isbn 0-9751933-6-8reefcatchments.com.au/files/2013/02/rcb631_mackay_coast...erosion prone area...

ISBN 0-9751933-6-8

© The State of Queensland, Environmental Protection Agency 2004

Copyright protects this publication. Except for purposes permitted bythe Copyright Act, storage, transmission or reproduction of all or anypart by any means is prohibited without the prior written permission ofthe Environmental Protection Agency.

Re488 January 2005

Produced by the Environmental Protection Agency

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Executive Summary 1

1 Introduction 3Study aimCurrent issuesStudy background

2 The study area 5IntroductionRegional settingMain geographical featuresHistorical overview

3 Coastal land use 9IntroductionLand use types

4 Geology 11

5 Soils 13IntroductionLandscape unitsAcid sulfate potential

6 Vegetation 17IntroductionVegetation associationsDune vegetation zonation andmanagementWeed managementVegetation conservation

7 Fauna 23IntroductionFauna of wetland habitatsFauna of terrestrial habitatsFauna of marine habitatsFauna and habitat conservation

8 Meteorology 27IntroductionClimatic summaryRainfall and hydrologyTropical cyclonesClimate variabilityClimate change

9 Water levels and currents 35IntroductionMean sea-levelTides and tidal flowsNumerical modellingOther influencesExtreme water levels

10 Waves 43IntroductionWave recordingWave hindcastingInshore wave conditionsExtreme eventsJoint probability of wavesand water levels

11 Surf zone processes 49IntroductionNumerical modelling

12 Sediment transport 51IntroductionLongshore transport modellingCross-shore sediment transport

13 Coastal topography 55IntroductionOffshore bathymetryTopographic features

14 Geological history 59IntroductionMean sea-levelPre-Holocene geologyHolocene deposition

15 Sediment supply and distribution 63IntroductionPioneer River tidal reachesPioneer River entranceTown BeachFar BeachShellgrit Creek to Bakers CreekHarbour Beach southHarbour Beach northLamberts BeachSlade Point BeachBypassing of Slade PointSlade Point western shoreBlacks BeachDolphin Heads and EimeoBucasia Beach

16 Coastal management 85IntroductionCoastal hazardsErosion prone area widthsShort-term erosionDune scarpingCoastline recessionSea-level rise due to climate changeResponse of tidal flats to sea-level riseStorm tide hazardCoastal management optionsRetreat optionBeach managementCoastal protection works

17 Management of individualbeaches 91IntroductionBakers Creek to Shellgrit CreekTown Beach and Far BeachPioneer River entranceHarbour Beach and Lamberts BeachSlade PointBlacks BeachDolphin Heads and EimeoBucasia Beach

18 Conclusions and recommendations 103IntroductionCommercial sand extractionEffects of the harbour wallsFuture monitoringSummary of Recommendations

Bibliography 107

Appendix A Aerial photography 111

Contents

Mackay Coast Study i

Tables

Table 1 Estimated resident population statistics by year . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Table 2 Breakdown of Mackay population by year . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Table 3 Population projections for Mackay area by year . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Table 4 Landscape units and soil types of Mackay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Table 5 Description of the vegetation associations found in Mackay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Table 6 Monthly and annual temperature and humidity statistics for Mackay in °C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Table 7 Mean daily evaporation (mm) for Mackay region 1889 to 1996 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Table 8 Average monthly and annual rainfall for Mackay region stations (mm) for 1870 to 1996 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Table 9 Highest and lowest annual rainfall values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Table 10 Tropical cyclone severity categories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Table 11 Tropical cyclones that crossed the coast within 50km of Mackay City . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Table 12 Predicted tidal planes for Mackay Outer Harbour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Table 13 Predicted storm tide levels for the Mackay region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Table 14 Recording periods, Mackay wave buoys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Table 15 Storm wave heights for selected return intervals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Table 16 Relative probability of tidal conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Table 17 Longshore current speeds and depths used in Unibest model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Table 18 Sediment sizes used in longshore transport model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

Table 19 Values of sediment and wave parameters used in sediment transport modelling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

Table 20 Predicted longshore transport rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

Table 21 Survey data analysis for Town Beach (refer figure 32 for location of profiles) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

Table 22 Survey data analysis for Far Beach (refer figure 32 for location of profiles) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

Table 23 Survey data analysis for Shellgrit Creek to Bakers Creek (refer figure 32 for profile locations) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

Table 24 Estimated sand and gravel extraction rates (103m3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

Table 25 Survey data analysis for Harbour Beach south (refer figure 32 for location of profiles) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

Table 26 Survey data analysis for Harbour Beach north (refer figure 32 for profile locations) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

Table 27 Survey data analysis for Slade Bay (refer figure 32 for profile locations) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

Table 28 Survey data analysis for Blacks Beach (refer figure 32 for location of profiles) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

Table 29 Survey data analysis for Bucasia Beach (refer figure 32 for location of profiles) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

Table 30 SBEACH parameter values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

Table 31 Storm erosion results, SBEACH (refer figure 32 for profile locations) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

Table 32 Estimates of potential long-term coastline recession . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

Table 33 Potential coastal recession associated with sea-level rise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

Table 34 Erosion prone area width calculations, Bakers Creek to Shellgrit Creek . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

Table 35 Erosion prone area width calculations, Shellgrit Creek to Illawong Park . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

Table 36 Erosion prone area width calculations, Illawong Park to Town Beach rock wall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

Table 37 Erosion prone area width calculations, Town Beach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

Table 38 Erosion prone area width calculations, East Point . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

Table 39 Erosion prone area width calculations, East Point to 800m south of the small craft harbour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

Table 40 Erosion prone area width calculations, immediately north of the Mackay Harbour breakwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

Table 41 Erosion prone area width calculations, Harbour Beach north . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

Table 42 Erosion prone area width calculations, Lamberts Beach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

Table 43 Erosion prone area width calculations, Slade Point Beach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

Table 44 Erosion prone area width calculations, Slade Point to McCready’s Creek . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

Table 45 Erosion prone area width calculations, Blacks Beach (south) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

Table 46 Erosion prone area width calculations, Blacks Beach (north) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

Table 47 Erosion prone area width calculations, Eimeo Beach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

Table 48 Erosion prone area width calculations, Bucasia Beach (south) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

Table 49 Erosion prone area width calculations, Bucasia Beach (north) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

ii Mackay Coast Study

Figures

Figure 1 Regional setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

Figure 2 Locality plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

Figure 3 Coastal geology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

Figure 4 Soil types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

Figure 5 Vegetation associations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

Figure 6 Habitat map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

Figure 7 Land–based monitoring sites: Pioneer River, Bakers Creek and Sandy Creek catchments and average

annual rainfall isohyets(mm) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27

Figure 8 Typical synoptic pattern, winter (30 June 1991) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28

Figure 9 Typical synoptic pattern, summer (3 January 1991) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28

Figure 10 Pioneer River peak flood discharge data at Mirani . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31

Figure 11 Mackay (Mount Bassett) wind roses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31

Figure 12 Tropical cyclone tracks impacting the Mackay region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32

Figure 13 Annual average occurrence of tropical cyclones, 1959–96 (based on Proh and Gourlay 1997) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33

Figure 14 Cumulative SOI data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33

Figure 15 1990 to 2100 sea-level rise for scenario IS92a (after IPCC 1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35

Figure 16 Data summary, S4 current meter (Oom shoal) 19–21 July 1992 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

Figure 17 Water level exceedance plot, Mackay Outer Harbour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37

Figure 18 Current measurement sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38

Figure 19 Location of Mackay waverider buoys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38

Figure 20 Peak mean spring flows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39

Figure 21 Effect on tidal velocities, pre and post Harbour construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40

Figure 22 Model results, Pioneer River medium flood event (5000m3/s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41

Figure 23 Fetch directions, Mackay waves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44

Figure 24 Percentage occurrence of wave height and period (1975–96; from DEH 1998) and wave direction from

composite wave record (1960–96) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45

Figure 25 Inshore directional wave climate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46

Figure 26 Comparison of inshore and offshore directional wave energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46

Figure 27 Directional distribution of extreme waves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .47

Figure 28 Predicted return period of tropical cyclone wave heights in the Mackay region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .47

Figure 29 Extent of sediment sampling by Jones (1987) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .52

Figure 30 Mean grain size versus sorting for sandy sediment units (from Jones 1987) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51

Figure 31 Cross–shore distribution of sediment transport at Harbour Beach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .53

Figure 32 Location of survey lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56

Figure 33 Representative beach profiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57

Figure 34 Pioneer River entrance (17/8/93) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .58

Figure 35 Slade Bay (14/8/93) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .58

Figure 36 Sea-level rise over the last 20,000 years (Gourlay and Hacker 1986) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .59

Figure 37 Geological history of Mackay region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .61

Figure 38 Sediment supply and distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .64

Figure 39 Location of sand and gravel extraction sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65

Figure 40 Aerial photograph, Town Beach to Harbour Beach south . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .66

Figure 41 Growth of Pioneer River tidal delta, 1962–93 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67

Figure 42 Bar topography, Pioneer River entrance, 1974–97 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67

Figure 43 Town Beach sand shoals (photography captured 17/8/1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69

Figure 44 Aerial photograph, Bakers Creek to Town Beach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .71

Figure 45 Aerial photograph, Harbour Beach north to Slade Point . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .74

Figure 46 Time series of upper beach movements, Harbour Beach north . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .75

Figure 47 Slade Point, 1962 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .76

Mackay Coast Study iii

Figure 48 Aerial photograph, Slade Point to Dolphin Heads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

Figure 49 Historical shorelines, Blacks Beach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .79

Figure 50 Aerial photograph, Dolphin Heads to Shoal Point . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .81

Figure 51 Historical shorelines, Dolphin Heads and Eimeo (photography captured 17/8/1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .82

Figure 52 SBEACH results for Harbour Beach (MAC122) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .87

Figure 53 Dune scarp component of coastal recession . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .87

Figure 54 Horizontal recession for Blacks Beach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .87

Figure 55 Area south of Pioneer River affected by 5m AHD storm tide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .89

Figure 56 Land tenure and revised erosion prone area widths, Bakers Creek to Town Beach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .92

Figure 57 Land tenure and revised erosion prone area widths, Town Beach to Harbour Beach south . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .94

Figure 58 Land tenure and revised erosion prone area widths, Harbour Beach north to Slade Point . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .96

Figure 59 Land tenure and revised erosion prone area width, Slade Point to Dolphin Heads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .99

Figure 60 Land tenure and revised erosion prone area width, Dolphin Heads to Shoal Point . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .102

iv Mackay Coast Study

The Mackay coastal region is characterised bya range of diverse natural features, including:

� a large tidal range, exceeding six metres;

� a network of sandy beaches including highdune systems;

� the Pioneer River estuary;

� substantial areas of coastal wetlandssupporting significant remnant lowlandhabitat; and

� extensive tidal flats, up to four km wide insome locations

The Mackay Coast Study was undertaken for theformer Beach Protection Authority as part of itscharter to provide advice and carry outinvestigations with respect to coastalmanagement. This report examines the 40kmsection of coast from Bakers Creek to ShoalPoint, to review and document the coastalresources and to describe the major coastalprocesses of the region. A number of generaland site-specific recommendations aredeveloped to guide future coastalmanagement decisions.

Site-specific investigations were undertakenfor the study, these include:

� data collection and assessment of coastalgeology and soils, including a review of thegeological history of the region;

� mapping of major vegetation associations;

� data collection and analysis of waves,currents, beach sediments and beachprofile surveys;

� numerical modelling of wave propagation,tidal hydrodynamics and sedimenttransport;

� assessment of available data relating tosignificant fauna and coastal habitats; and

� review and analysis of meteorologicalconditions.

The principal findings of the study arefocussed on issues relating to physicalcoastal processes. This includes a review of erosion prone areas for the region.

A number of areas of active coastal recessionthat may require management actions havebeen identified. These include parts of FarBeach and the northern section of HarbourBeach. The latter is the result of thecombined effect of the Mackay Harbourbreakwaters and the permitting ofcommercial sand extraction.

Along many parts of the Mackay coast,development has been allowed within theerosion prone area. This has led to theconstruction of protective rock walls and theassociated adverse effects on the adjacentbeaches. These areas, along with other low-lying suburbs set back from the shoreline,are subject to the risk of storm tideinundation. An important managementresponse against the threat of coastalerosion and storm tide flooding is themaintenance of the natural protectionafforded by the primary dune system.

It is concluded that coastal resources in theMackay region are highly sought after forcompeting uses including residential,commercial, tourism and recreation. Effectivemanagement is necessary to ensure that thenatural values and attributes of the coast arepreserved while economic development andexpected population growth areaccommodated. This report providessufficient detailed information on which tobase future coastal management decisions.

Executive Summary

Mackay Coast Study 1

Lamberts Beach.

2 Mackay Coast Study

Study aimThe favourable climate and the historicalpattern of development along the Queenslandcoast have led to widespread communityacceptance of the State’s beaches as valuablesocial assets. The recreational opportunitiesthat beaches provide and their naturalattractive appearance have encouragedextensive residential and commercialdevelopment of beach areas, often as closeas possible to the beach itself.

Aside from their recreational value and theirimportance as assets to tourism, beachesare an important component of the coast’snatural protection. The maintenance of widesandy beaches and well-vegetated dunesystems provides a natural barrier to stormwave energy and protects inland areasagainst extreme water levels. This feature isof particular importance in low-lying coastallands that can be prone to flooding.

A detailed knowledge of coastal processes isvital for effective coastal management andplanning. This report documents the resultsof an investigation into coastal processesoccurring along the Mackay coast in centralQueensland (a regional view is shown infigure 1). An overall view of regional coastalprocesses is presented, as well as detaileddescriptions of individual beaches in thestudy area. Recommendations on managementoptions for specific issues and individualbeaches have been developed, using theavailable information.

Current issuesPresent-day shoreline movements along theMackay coast are the natural consequencesof wind, wave and current forces acting onthe beach system. Similar movements havebeen occurring along this coast for thousandsof years. The beaches have remained becausenatural beach processes tend to maintain adynamically stable beach form, even wheresubstantial movements occur. In general, it isbeneficial to maintain these natural coastalprocesses so that they can continue unhindered.

Beach erosion is commonly regarded as aproblem only when it represents a threat toproperty and improvements. The cause of theloss of the beaches themselves is oftenoverlooked when the adjacent development

is under threat. However, the main issue isnot that beaches erode, but that developmenthas occurred within the zone of natural beachmovements. In many instances, attempts toprotect development from wave attack resultin degradation of the adjacent beaches, andachieve only limited success in propertyprotection, the original purpose. Thus, theproblems associated with deterioration ofrecreational beaches and erosion threat todevelopment are related.

At present, a large proportion of the beachesin the study area can accommodate shorelinechanges due to beach erosion withoutdetracting from the quality of the beach.However, in some areas erosion has threateneddevelopment, necessitating propertyprotection works that have resulted in theloss of the adjacent beach as a recreationalasset. While very few private properties areunder threat, increasing developmentpressures may create undesirable situationsunless adequate planning and managementconsiderations are incorporated into futuredevelopment proposals.

The continued existence of beaches in a form in which their aesthetic and recreationalpotential can be fully realised is threatenedin areas where artificial restraints have beenimposed on natural beach behaviour. As aresult of such interference, costly remedialaction is often necessary to prevent completeloss of the beach and to protect existingdevelopment from the threat of erosion.

Remedial action can range from expensivemajor works to relatively cheap managementprograms, depending on the nature of theproblem. Identification of the most appropriateremedial action is not simple and must bebased on an accurate explanation of the causeof the problem. The financial resourcesavailable to local authorities for beachprotection works are generally limited,increasing the need for such funds to be usedefficiently. The consequences of incorrectdecisions in beach protection matters can befinancially severe and physically disastrousfor the beach, thus beach protection proposalsneed to be based on a thorough knowledgeof local beach behaviour.

The commercial extraction of sand forreclamation of coastal lands and as rawmaterial for the construction industry has

been undertaken for many years in theMackay region. Sand extraction has beenfocused primarily around the Pioneer Riverand the adjacent beaches. The demand forcontinued access to these resources isexpected to continue.

The coastal issues that require specificconsideration in the Mackay region include:� natural, episodic beach erosion caused by

storm events;� fluctuations in the characteristics of tidal

inlets, particularly near the Pioneer Riverentrance;

� the risk of storm tide inundation;� the sustainable use of sand and gravel

resources;� effects of the Mackay Outer Harbour walls

on adjacent coastal processes; and� vulnerability of coastal areas to sea-level

rise and climate change.

Study backgroundThis study of coastal behaviour in the Mackayregion has been completed in accordancewith section 34 of the Beach Protection Act1968, which includes:

a) the giving of advice and making of reportswith respect to coastal management to theMinister, State Government departments, the Marine Board, local authorities, riverimprovement trusts and other persons; and

b) the carrying out of investigations,conducting of experiments and giving ofdemonstrations with respect to coastalmanagement.

In order to complete the study, the followingdata was required:

� physical description of beaches andhinterland;

� historical record of coastal developmentand coastal changes;

� photogrammetry of recent and historicalaerial photography of the area;

� water levels and currents;� meteorological conditions;� waves;� soils;� vegetation;� geology; and� beach profile surveys.

1 Introduction


IntroductionThe Mackay Coast study area is limited toabout 40km of predominantly sandy coastlineextending from Bakers Creek in the south toShoal Point in the north (figure 2). It containsdiverse natural physical features including:

� extensive tidal flats;

� estuaries and wetlands;

� sandy beaches, dune systems and rockyheadlands; and

� rocky islands and shoals.

Features such as rocky headlands, estuariesand rivers separate the coast into segmentedbut not necessarily isolated units. Behind the coastal barrier are substantial areas ofmarginal lowland. These typically containmangroves and marshland habitat that areimportant to marine and terrestrial fauna.

The study area lies fully within the MackayCity Council administrative boundary. MackayCity is the result of an amalgamation in 1994of the old Pioneer Shire Council and the thensmaller Mackay City Council. The localgovernment is now responsible for an area ofabout 3000km2 extending from Alligator Creekin the south to the O’Connell River in the north.The Mackay Port Authority is responsible forapproximately 200km2 of this area.

Regional settingThe Mackay region is centred around latitude21°10' south; the Great Barrier Reef and anumber of islands lie offshore. The region isbacked by the Clarke and Connor Ranges,which encompass the well-known EungellaNational Park and Finch Hatton Gorge.

The Mackay district falls within the CentralQueensland Coast bioregion (Sattler andWilliams 1999). The area is generally warm,wet and humid, although it can become verydry in winter and spring. The region is subjectto occasional severe cyclones that can causewidespread damage from high winds, coastalflooding and severe waves.

Much of the native vegetation has beenreplaced by agriculture and some urbandevelopment, especially in the lowland areas.A large proportion of the Mackay regionsupports a prolific sugar industry. Sugarcane

was introduced to the area in 1865 and the firstmill opened two years later. Since then, thePioneer valley has become one of Queensland’smajor sugar-producing areas, producing 1.61million tonnes of refined and raw sugar in 1997resulting in gross revenue of $532 million. Theregion’s production covers an area of about117,000ha, and represents about one-thirdof the Queensland total.

Beef production in the upper parts of thePioneer River catchment occupies about50,000ha and has an estimated value of$4 million. Forestry is also an importantindustry in the Mackay region.

Urban land has historically been limited.Urban expansion now poses pressure,especially in coastal areas that are currentlyused for agriculture.

2 The study area


Dolphin Heads and Blacks Beach in the background.


Figure 2 Locality plan

Mackay City Council has recognised thispressure and its strategy for urbandevelopment is directed at preserving arableland on a priority basis.

The Pioneer River is the predominantcatchment in the region; its area is 1,489km2.The catchment is relatively small comparedwith the Fitzroy River, located further south,with a catchment area of 142,645km2. Theaverage annual flows for the Pioneer andFitzroy Rivers are 900 million m3 and 6,000million m3 respectively.

The City of Mackay, with a population of62,548 in 1998, is the major service centrein the region. It serves the coal mininginfrastructure in the Bowen Basin to the west, as well as providing services to theagricultural industry and port-relatedfacilities.

Main geographical featuresThe major feature on the coast is the PioneerRiver, which divides Mackay into two areasof development. Weirs have been built atDumbleton, Marian and Mirani. The river istidal up to Dumbleton Weir, 16.5km from theriver mouth. In times of flood the PioneerRiver can be expected to deliver large quantitiesof water and sediment to the coast. Trainingwalls to improve navigation and for bankprotection have altered the natural river bankof the lower estuary.

The other significant catchment in the studyarea is Bakers Creek, a previous course of thePioneer River in relatively recent geologicaltimes. Shellgrit, McCreadys and Eimeo Creeksare other smaller watercourses flowing directlyinto the Pacific Ocean.

To the east and south of the Pioneer River areTown and Far Beaches, which feature extensivetidal flats. These intertidal areas, more thanthree km wide in places, form part of a largenearshore sediment deposit extending intoSandringham Bay. Much of the coastal areasouth of the river has been significantlyaltered by development activities over thepast 50 years.

To the north of the Pioneer River entrance isHarbour Beach, with Slade Point andLamberts Beach at its northern extremity.Near the centre of this section is the MackayOuter Harbour, with associated industrial

areas and the recent small boat marinadevelopment. Harbour Beach is the home ofthe Mackay Surf Lifesaving Club and has apatrolled swimming beach.

Further north is Blacks Beach, the longestcontinuous stretch of beach in the Mackayarea. Named after M.H. Black, the localMember of State Parliament in the 1880sand 1890s, it has been a popular holidaydestination for the local community since the1870s. Major tourist development started inthe 1970s, with holiday apartments, units,resorts and caravan parks being built alongthe shore.

Dolphin Heads, named for the resemblance ofthe headlands to the heads of two dolphins,is at the northern end of Blacks Beach. It hasa few private residences and a beachfrontresort. Eimeo, to the west of the headlandand overlooking Sunset Bay, has a number ofholiday units and a popular cliff-top hotel.

The northernmost beach in the study area isat Bucasia. Originally named Seaview, thetownship of Bucasia was renamed after FatherPierre Bucas, who ran an orphanage in Mackayfrom the early 1870s. It became a popularbeach and the Pioneer Shire Council builtconveniences and a bathing shed in 1923 toserve up to 200 people who camped thereduring holiday periods. More recently, resorts,caravan parks and holiday units have beenbuilt along the beachfront.


Pioneer River showing Cullen Island in the foreground.

Historical overviewFor thousands of years the coastal districtwas inhabited by the Yuwi community. TheYuwi lands stretch from Rabbit Island in thenorth to Cape Palmerston in the south. TheYuwi people relied on coastal resources andwere noted fish and shellfish eaters. Fishtraps can still be seen in Sand Bay just northof the study area.

The Mackay coast was surveyed in 1819 byLieutenant Philip King, and was first settledby Europeans in the early 1860s after theseparation of Queensland from New SouthWales in 1859. John Mackay arrived in 1860,in the company of seven other men, lookingfor new pastures for cattle. He was soonfollowed by other settlers. The settlement ofMackay was founded in 1862 and was declareda town in 1866. It has remained the servicecentre for the region despite considerabledifficulties in the provision of an adequateport for many years.

In 1862 the government ship Pioneer, under thecommand of Commodore Burnett, surveyedthe Pioneer River for a harbour. Agriculturewas centred around cattle and sheep farmingbefore sugar production began in 1865.

Mackay, six km from the river entrance, becamean official port in 1863. From the beginning,the depth of water and strong currents in theriver posed a problem for navigation. Wharvesand associated port infrastructure were builtalong the south bank of the river to handlesmall vessels. Larger vessels however, had toanchor at high water in the lee of Flat TopIsland, 4.5km south-east of the entrance, totransfer both cargo and passengers by lighter.

Over the next 75 years continual efforts weremade to improve shipping conditions withinthe river by dredging and construction of rocktraining walls. Many schemes to connect themainland to a proposed new port area atFlat Top Island were developed but did noteventuate, mainly because of the high cost ofconstruction. Some benefit was gained whenthe river broke through the northern bank at theentrance during a cyclone in 1898, forming animproved channel. However, the improvementwas short-lived and eventually a decision wasmade to construct a new port on the coastnorth of the river entrance.

Work began on the new harbour in 1935 andthe port was officially opened on 26 August,1939 by the Premier, the Hon. W. Forgan-

Smith. It was connected to Mackay and thehinterland by both road and rail. The numberof vessels currently using the port is still lowerthan the number that visited the river port in1926. However, the tonnage of cargo throughthe port has increased from about 110,000tonnes in 1926 to more than 2.5 milliontonnes in 1997 to 98.

The Pioneer Shire Council was formed in 1902,replacing the previous Divisional Board. TheCouncil initially had powers in the areas ofrailway building, town planning, health, publichalls and agricultural drainage. The City ofMackay was declared in 1918, and in 1994the adjacent Pioneer Shire Council wasabsorbed into Mackay City Council.


Mackay Harbour in 1997 prior to construction of the small boat harbour.

IntroductionSteady growth has been observed in theMackay region since settlement, coupledwith intermittephases of rapid growth andeconomic upturns in agriculture and farming.This expansion has largely been attributed tothe sugar industry, which remains the mostimportant regional industry. Increasedsugarcane production resulted in theestablishment of additional sugar mills,roads, a port and other services. Industriesother than agriculture usually fall into thecategory of service industries for the ruralsector and commerce. More recently, thetourism industry has played an increasinglyimportant role in the regional economy.

Mackay City Council’s Strategic Plan (MackayCity Council 1999) shows broad land usedesignations throughout the study area.Of interest are the following features:

� the extensive areas of coastal landsdesignated ‘Open Space and Recreation’;

� a new area of tourism developmentplanned for East Point, south of theharbour;

� planned completion of the reclamationworks in East Mackay, which will provideadditional residential areas and enable the connection of the road (BinningtonEsplanade) between Town Beach and Far Beach; and

� possible expansion of tourismdevelopment at the northern end of TownBeach adjacent to the Pioneer River.

Land use types

ResidentialExtensive areas of coastal land in thestudy area are used for residential purposes.A number of residential properties arelocated adjacent to the shoreline. In somecases, coastal erosion has threatenedproperties and prompted the construction of

rock walls. These have become significantfeatures along a section of Blacks Beach.Additionally, many residential areas arerelatively low-lying and are subject to the riskof flooding and storm-tide inundation.

Many residential areas south of the river havebeen reclaimed using coastal sand resources.At Town Beach reclamation works in 1964created a deep hole just offshore. Thedredged area, which is still visible, resultedin an erosion threat to the esplanade road,necessitating the construction of a rock wall.

A notable operation was carried out in 1985when the Land Administration Commissionremoved 280,000m3 of material from an area500m offshore to raise the level of aresidential area in East Mackay.

The population of the City of Mackay hasincreased steadily over the past few years(table 1). A large proportion of thepopulation growth has been in the northernMackay beach suburbs (table 2). Theincrease in population in the region isexpected to continue (table 3 shows theAustralian Bureau of Statistics populationprojections until the year 2011).

Recreation and tourismThe Mackay tourism industry is expanding andhas an estimated total annual turnover of$250 million. The coastal areas around Mackayhave been visited for recreation and fishingsince the late 19th century. Tourism was notsignificant until the late 1940s, when tours to

inland national parks and the Great BarrierReef islands began. Motels, caravan parksand resort developments at Far Beach andthe northern beaches are relatively recentand are competing with residential use forlands along the beachfront.

Statistics for the region show that the numberof official guest rooms is increasing at anannual rate of approximately four percent(Mackay Tourism and Development Bureau1998). A number of developments have beenrecently completed in the northern beachareas, including significant integrated resortand marina infrastructure at Harbour Beach.

Town Beach and Far Beach are close to thecity centre and are popular with both local

3 Coastal land use


Binnington Esplanade and protective rock wallat Town Beach.

Table 1 Estimated resident population statistics by year.

1987 1992 1997 Annual change Annual change1987 to 1992 1992 to 1997

Mackay City 51 597 55 895 62 442 +1.7% +2.3%

Queensland 2 675 107 3 032 834 3 401 232 +2.7% +2.4%

Table 2 Breakdown of Mackay population by year.

1991 1996 Annual growth rate 1991 to 1996

Persons Dwellings Persons Dwellings Persons Dwellings

Bucasia 2 009 749 2 398 913 3.9% 4.4%

Eimeo 918 330 1 357 524 9.6% 11.8%

Blacks Beach 627 252 820 233 6.2% –1.5%

Shoal Point 477 178 622 236 6.1% 6.5%

Mackay City 41 012 15 041 44 880 17 298 1.9% 3.0%

Table 3 Estimated resident populationstatistics by year.

Projection 2006 2011

High 86 030 93 220

Medium 82 810 88 040

Low 80 410 84 260

residents and tourists. Views of Round Topand Flat Top Islands, and the huge expansesof sandflats at low tide are an attraction.

Mackay is a departure point for island resortsand visits to the Great Barrier Reef. A number ofcruise boats and charter fishing boats are alsobased in Mackay. Moorings in the new smallcraft harbour provide facilities for larger vesselsthat use the fishing grounds off the coast.

Recreational fishing is a popular pastimethroughout the study area. Boat ramps givesmall boats access to creeks and nearshorefishing areas. Shore-based fishing is commonalong the area’s beaches and headlands.

CommercialCommercial fishing initially supplied only thelocal market, but since 1930 the industry hasdeveloped substantially. In 1934, 78 licenceswere issued at Mackay, increasing to 824 in1948, with 258 fishing boats and a yield ofabout 160t. By 1956, Mackay’s production wasabout three percent of the total Queenslandcatch and ten percent of the State’s barramundicatch. In 1970/71, 72t of mostly reef fish and67t of prawns were landed. By 1997/98, thetotal catch had reduced to 70t.

Although the aquaculture industry is developingthroughout the central Queensland coastalregion, it has not yet become significant inthe study area.

Sand and gravel extraction from the lowerreaches of the Pioneer River and coastal areasis a significant commercial activitysupporting the local economy. Over the lasttwo decades an average of 100,000m3 ofsand and gravel was removed annually fromthe lower reaches of the Pioneer River for theconstruction industry.

Significant quantities of sand are alsocommercially extracted from Bakers Creek,with an annual limit of 50,000m3. From 1984 to1990, permission was given annually to dredgeup to 40,000m3 of sand from the intertidalarea north of the entrance of Bakers Creek.However, the actual quantity reported ashaving been removed was below this limit.The section of Harbour Beach south of theharbour has provided a regular source of sand,with annual average extraction rates of theorder of 40,000m3 over many years.

A number of reclamation works using coastalsediments have been completed as part of thecity’s development. In 1978 about 620,000m3

of material was dredged from the PioneerRiver near Mackay city centre (Cullen Island)to reclaim the Caneland Shopping Centre sitenear the city centre. Extensive areas south ofthe Pioneer River have also been reclaimed,

mainly for residential development.

Weirs have been constructed on the PioneerRiver at Dumbleton, Marian and Mirani toprovide water for agriculture and for urbansupplies. These weirs have significantlyaltered the characteristics of the river andtheir effects are noticeable for manykilometres upstream.

Port of MackayThe Port of Mackay is an important part of thelocal economy, providing a valuable servicefor the export of sugar and grain, and theimport of petroleum, fertiliser and magnetite.The Mackay Port Authority also manages thelocal airport.

The construction of the harbour between 1935and 1939 was successful in establishing aport with largely all-weather and all-tide accessto most commercial shipping, thus overcomingnavigation problems in the river entrance.Relatively minor maintenance dredging isrequired to remove fine sediments thatbecome trapped in the low-energy conditionscreated by the harbour walls. As there are nosignificant freshwater inflows to the harbour,the major source of fine sediments is fromthe exchange of water with the nearshoretidal flows. Most of the material dredged fromthe harbour to maintain required depths isplaced in a disposal area approximately fourkm offshore from Slade Point.

Previously, capital dredging works have beencompleted to deepen various sections of theharbour. The dredged material was mainlysand and was typically pumped over thenorth wall of the harbour into the littoral zone.

ReservesThe only national park within the study areais the Reliance Creek National Park (14ha),located seven km west of Bucasia. The studyarea has two conservation parks. One (46ha)is located on the northern bank at theentrance to Bakers Creek and is a recurvingspit with mangrove stands providing animportant marine habitat and a nesting sitefor birds. The other is a geological formationat Mount Hector.

A special conservation reserve at thenorthern end of Harbour Beach, known asthe Slade Point Reserve, is managed jointlyby the Mackay City Council, the Departmentof Natural Resources, Mines and Energy andthe Environmental Protection Agency. Thisarea is especially important as it isrepresentative of the natural vegetationpatterns of the Mackay region. The AustralianHeritage Commission has placed the area onthe Interim List of the Register of the National

Estate. The area was nominated because ithas been identified as containing regionallysignificant vegetation and fauna communities.South of the Slade Point Reserve is a similararea maintained (for conservation purposes)by the Mackay Port Authority. Together, theseareas comprise an important tract of remnantwetland and dune system close to the urbanand industrial development of northernMackay.

‘Important Wetlands’ form the northern andsouthern boundaries of the study area(Commonwealth of Australia 1996). Theseare Sandringham Bay/Bakers Creek to thesouth, and the Sand Bay Wetlands north ofShoal Point. The Sandringham Bay/BakersCreek aggregation consists of freehold,leasehold and vacant Crown land. Sand Bayis a Fish Habitat Area (Management A) and ispartly State Marine Park, with the remainderconsisting of freehold and leasehold land.Both areas are significant because they areexamples of marine and estuarine wetlandsof the Central Queensland Coast bioregion.They have extensive expanses of intertidalmudflats backed by mangrove forest, and areparticularly important as fish and shorebirdhabitat.

Bassett Basin in the estuary of the PioneerRiver was declared a Fish Habitat Area(Management B) in 1993. It was previously awetland reserve and is managed to enhanceexisting and future fishing activities byprotecting fish habitat. The area consists ofsubstantial mangrove forest and tidal creeksthat are fish nurseries.


Slade Point Reserve.

Most studies of the coastal geology of theMackay region are based upon the Bureau ofMineral Resources regional study (Jensen etal. 1966). Three studies were commissionedby the Beach Protection Authority:

1. The Geological Survey of Queenslandundertook a seismic profiling survey in theregion from the Hillsborough Channel inthe north to Hay Point in the south,including interpretations of the shallowseismic stratigraphy in the area (Hegarty1983).

2. In 1986, the Geological Survey ofQueensland (Jones 1987) reported on thedistribution of the nearshore sedimentsnear Mackay, including an examination ofmore than 300 sediment samplescollected during March and April 1986.The report describes the distribution ofsediments along the Mackay coast, infersdirections of sediment transport, andinvestigates possible transportmechanisms.

3. The Water Resources Section of theDepartment of Natural Resources (formerlyin the Department of Primary Industries)studied terrestrial geology (DPI 1995). Thereport contains detailed descriptions ofgeomorphology, stratigraphy, agestructure, depositional processes and adiscussion of evolutionary models.

The coastal geology of the study area issummarised in figure 3. The surface geologyof the coastal region is dominated by twogroups:

� the primarily Palaeozoic (in the order of200 million years in age) volcanic andsedimentary bedrock outcrops of theCampwyn Beds. Examples of these outcropsinclude the prominent headlands, SladePoint, Dolphin Heads and Shoal Point; and

� the relatively recent Holocene (up to10,000 years in age) deposition of coastalsediments comprising the extensivesystem of sandy beaches formed throughthe region.

These two groups make up the majority ofthe coastal features in the Mackay region.Pleistocene age (2 million to 10,000 yearsbefore present [BP]) sedimentary depositsoccur extensively through the terrestrial partof the area, although the coastal exposuresare relatively limited. Exposures of these stiffclays can be seen in the mouths of Bakersand Shellgrit Creeks.

Pleistocene sediments are generallycomposed of silty clay to clayey sand andsometimes contain calcareous nodules.Colours range from mottled orange-brown togrey-green. Some areas of unconsolidatedPleistocene sediments are also found; theseinclude relict beach ridges north of thePioneer River. Part of the active nearshorezone also includes sediments derived fromthe Pleistocene period.

Analysis of records from a number of drillingprograms has enabled an estimate to bemade of the approximate underlyingPleistocene surface near the coast. From this,a representation of the historical shorelineprior to the most recent phase of Holocenedeposition was derived and preliminaryestimates of a sediment budget made (DPI 1995).

Discussions of the geological history and thepresent-day coastal sedimentation regimesare provided in later chapters.

4 Geology


The entrance Bakers Creek.

IntroductionThe Queensland Department of NaturalResources surveyed and mapped the soils ofthe Mackay coast on behalf of the BeachProtection Authority. Figure 4 provides asummary of the findings.

Landscape units are defined as areas oftopographic and geomorphic similarity. Soiltypes are defined as a group of soil profilesthat can be grouped according to the similarityof their morphological characteristics, andtheir occurrence is coherent enough to berepresented on a map. The study area hasbeen divided into four major landscape unitscontaining ten soil types (table 4).

Landscape units

Quaternary beach ridgesQuaternary beach ridges are comprisedpredominantly of siliceous sand dunes ofvarying heights. Up to four sets of dunesextend from the frontal dune. The dunesoften overlie the watertable at the margins ofestuaries, swamps or flood plains and haveburied mangroves and saline flats.

Andergrove soils are poorly sorted siliceoussands. They consist of littoral and aeoliandeposits of coarse-textured yellowish-brownsands. Coarse sands dominate, with a coarseto fine sand ratio usually greater than 1:4.This ratio is at a maximum in the hind dunesand at a minimum in the frontal dunes.Nutrient levels and water-holding capacityare extremely low in all Andergrove soils.Most of the urban development within thesurvey area has occurred on this soil type.

The watertables associated with theAndergrove watertable variant soil unit nearthe airport and at Shoal Point have extremelylow pH levels (less than 3.0) therefore, theacid sulfate potential of these areas is veryhigh. Watertables from the other areasranged in pH from 4.0 to 8.8, which may berelated to the presence of calcareous sandsediments.

Small areas of calcareous sands are alsofound on either side of the mouth of thePioneer River. These sands have high pHlevels (greater than 8.0 at depth), and oftenhave small rounded pieces of pumice on thesurface and shell grit in the soil profile.

Estuaries, swamps and flood plainsThis landscape unit comprises mangrovesadjacent to creeks, freshwater swamps, andsupratidal and intertidal flats. Cracking clayareas appear to have buried former areas ofsaline flats. All soils in this landscape unitgenerally have high to extreme acid-sulfatepotential.

Dundula soils are dark-grey cracking claysoils found in low-lying areas adjacent tomangroves. The soil is characterised by itsrelatively high clay content (35 to 40 percent).Because of the clay content and its landscapeposition, the soil is subject to frequentwet-season waterlogging and in some yearsmay not dry sufficiently to exhibit surfacecracking.

Fertility is moderate to high throughout theprofile. The pH is acid to neutral, althoughthis soil exhibits a very strong acid-sulfatepotential and high salinity at depth.

Saline flats and mangrove soils are high infertility, clay content, chloride and salinitylevels. The pH is neutral on the surface,decreasing to a very low level (3.5 at andbelow 1.5m soil depth), indicating a veryhigh acid-sulfate potential. Saline flats tendto be inundated only on large tides.

Swamp areas are subject to significantpermanent or seasonal freshwater ponding,generally adjacent to hind dunes. The largestoccurrence is in the Slade Point area.

These soils are loamy, being dominated100:1 by fine sand rather than coarse sand,although coarseness increases with depth.Fertility is moderate and decreases withdepth. The pH is moderately acid (5.7 to 6.3)and decreases significantly with depth. Thelow pH values may indicate a high acid-sulfate potential.

5 Soils


Table 4 Landscape units and soil typesof Mackay

Landscape unit Soil types

Quaternary Andergrovebeach ridges Andergrove watertable variant

Andergrove calcareous variant

Estuaries, swamps Dundulaand flood plains Mangroves

Saline flatsSwamps

Relict levees CameronPioneer red B horizon variant

Rises and hills Habanaon Andesite

Relict leveesRelict levee areas located away from thepresent coastline are often two to three metreshigher than the surrounding mangrove ordune areas, and have very contrasting soilsand vegetation. A small relict levee occursjust south of Mount Bassett.

The Cameron soil type is an alluvial brownuniform loam located on a slightly elevatedridge south of Mackay Airport. This soil areahas mostly been cleared and cultivated forsugarcane.

Loam textures are dominant in the subsoil,although the surface is often sandy and asandy buried layer is evident below 1.5m soildepth. The coarse to fine sand ratio is low,being less than 0.5 in the subsoil. Fertilitylevels are low and the pH is moderate(5.5 to 6.5). A very low pH (3.2) is evident inthe buried sandy layer, this reflects the acid-sulfate potential of this layer.

The Pioneer red B horizon variant is a neutralred duplex soil. It occurs on pronouncedridges above surrounding Andergrove soilsand mangrove or freshwater swamp areas.This soil has a sandy topsoil directly overlyinga red clay subsoil. The depth of topsoil variesfrom 25 to 35cm. Fertility levels appear to begood. Most of these areas have been clearedand cultivated to grow sugarcane or treecrops such as mangoes. The pH is neutraland salinity levels are very low.

Rises and hills on AndesiteA well-structured brown clay is associatedwith the low rises and hills on Andesite orsimilar volcanic rocks. This soil has varyingdepth to rock and a varying cobble amountwithin the soil profile. Rock areas are definedas areas of outcrop with little or no soil. Theyoccur north of the river at Mount Bassett,Slade Point, Dolphin Heads, Eimeo andShoal Point.

Habana is a brown well-structured clay soilwith a maximum soil depth to rock of about0.6m. Slopes of the land vary from twopercent in the less sloping areas to greaterthan 30 percent in the steeper areas.

Habana soil is a uniform clay soil (30 to40 percent clay) or a gradational soil with aclay loam topsoil (25 to 30 percent clay) witha gradually increasing clay content withdepth. The subsoil colours range from brownto reddish-brown. The profile is well-structured throughout, with general fertilitymoderate to high. The pH is generally neutraland salinity is low.

Areas such as Mount Bassett where there isabundant rock and little or no soil have beenmapped as rock. Areas of Habana withdeeper soil and less surface rock have beenused for sugarcane cultivation, although mostof these areas have now been developed forurban purposes and have been mapped asdisturbed in this survey.

Stability of slopes under urban developmentis a major concern within the survey area; inparticular the risk of mass movement(landslides) in the steeper areas.

Acid sulfate potentialA major acid-sulfate potential exists in manysurvey areas due to the history of formationof some of the soils and landscapes. Allareas of existing estuaries, swamps andassociated flood plains generally have highto extreme acid-sulfate potential.

Areas that have been buried by more recentdeposits, such as in the Bakers Creek areaand at Shoal Point (west of the Mackay–Bucasia road) also have high acid-sulfatepotential.

The relict levees, rises and hills on Andesiteand most of the sand dune areas appear tohave little or no acid sulfate potential. Theexception is the Andergrove watertablevariant soil type. Analysis of the watertableindicates that it has very low existing pH andhigh acid-sulfate potential at specificlocations.


Bedrock outcropping Harbour Beach north.

IntroductionBeach Protection Authority commissionedthe Queensland Herbarium to undertake avegetation and floristic survey of the Mackaycoast, extending south to Hay Point(Batianoff and Franks 1997). A detailedvegetation survey of the area immediatelynorth of Mackay Harbour was conducted forthe Mackay Port Authority. Sattler andWilliams (1999) also detail the regionalecosystems of the area.

The study area is dominated by rural land (48 percent) and urban land (13 percent).Land with remnant native vegetation coversabout 33 percent of the study area. Theremnant native vegetation is comprised ofwetlands (80 percent) and terrestrialvegetation (20 percent).

A total of 1,123 species of plants have beenrecorded. Of these, 800 (71 percent) arenative, 310 (28 percent) are exotic, and 13 (one percent) are Australian plants notindigenous to the Mackay area. Elevenvegetation associations have been mappedin the study area (figure 5 and table 5).

Vegetation associations

Saline flatsSaline flats are the most extensive vegetationassociation found in the study area. Theyinclude areas of mangroves and intertidalherblands. Extensive tracts occur aroundReliance Creek, Slade Bay, Bassett Basin,Bakers Creek and Sandringham Bay.

Mangroves cover 19 percent of the study areaand 74 percent of all intertidal vegetationareas. Twenty-one mangrove species wererecorded, representing just over half of the38 known Australian species. The mangrovestructural formations of Mackay vary fromclosed forests to low scrublands, with two toeight metre high closed scrubs being mostcommon. Many communities consist ofmonospecific stands of Ceriops tagal,Rhizophora stylosa and Avicennia marina.

Intertidal herblands cover the remainingintertidal vegetation areas. Intertidalherblands are comprised of saltmarsh andsaltpan vegetation. These areas occur on thelandward edge of the intertidal zone. The soilsare often hypersaline due to evaporation andinfrequent tidal inundations. The intertidalherblands vary from open herbland to closedgrassland. They are usually dominated bySporobolus virginicus.

Sandy seashore, strand andlittoral vegetationSandy seashore vegetation is found ondunes along exposed and sheltered beaches.Mackay’s sandy seashore vegetationconsists of 227 species, 40 percent of whichare introduced. Beach strandline herblandsoccur on high-energy sandy coasts on mobileforedune areas.

6 Vegetation


Table 5 Description of the vegetation associations found in Mackay

Vegetation association Sub-units and description

Saline flats a) Mangroves — vary from closed forests to low scrublands; 21 species recorded; communities vary from monotypic to mixed stands.

b) Intertidal herblands — vary from open herbland to closed grassland; Sporobolus virginicus is widespread.

Sandy seashore Strandline — foredunes colonised by Spinifex sericeus open grassland, landward of which is an Ipomoea pes-caprae zone.

Casuarina woodland — dominated by Casurina equisetifolia var. incana.

Casuarina woodland with beachscrub — dominated by C. equisetifolia var. incanawith rainforest species scattered throughout.

Freshwater swamp with Freshwater wetland areas of swamp grasslands, swamp sedgelands treeless herbland and open water herblands.

Freshwater swamps Melaleuca leucadendra open forest — dominated by M. leucadendra often forming with melaleuca monospecificstands and found in low-lying areas.

Melaleuca dealbata open forest — dominated by M. dealbata with the occasional eucalypt species such as E. platyphylla and E. tereticornis growing on coastal beach ridges. These areas are drier than the areas where M. leucadendra dominate.

Melaleuca viridiflora open forest — dominated by M. viridiflora. Often with eucalyptemergents. Found on wet dune sandy soil. Regrowth areas characterised by monospecific stands of M. viridiflora.

Riparian forest Estuary riparian forest — occurs on lower reaches of tidal waterways. Intertidal marginssupport mangrove low closed forest dominated by Rhizophora stylosa and Avicenniamarina and landward areas support eucalypt/melaleuca open forest.

Tidal mid-reach riparian forest — narrow band of mangroves usually dominated by Aegiceras corniculatum with adjoining eucalypt open forest.

Freshwater mid-reach riparian forest — occurs on levee banks. Includes wetland vegetation and gallery forests.

Freshwater upper-reaches riparian forest — consists of mixed gallery open forest dominated by Casuarina cunninghamiana subsp. cunninghamiana.

Lowland littoral rainforest Emergent sparse canopy dominated by Terminalia sericocarpa. Includes mid-dense tree canopy, an understorey of tall shrubs and sparse groundcover.

Hill and headland rainforest Range from simple to complex notophyll vine forests.

Eucalypt open forest Corymbia tessellaris open forest.including a number ofdifferent forest types

Eucalyptus crebra open forest.

Mixed eucalypt open forest.

Beach scrub Patches of rapidly growing rainforest species growing on sandy seashore areas.

Rocky shore vegetation Closed grassland and closed herbland that grow on rocky shores.

Disturbed Vegetation cleared for cultivation or development.

These unstable beachfront areas arecolonised by Spinifex sericeus opengrassland. S. sericeus open grassland occursas a continuous zone along Harbour Beach,Shoal Point to Blacks Beach and Far Beach.

A second band of strand herbland is foundlandward of the S. sericeus open grassland. It usually includes Ipomoea pes-capraesubsp. brasiliensis. In sheltered areas andalong low-energy sandy coasts, strandherbland is more prominent and replacesS. sericeus open grassland. The strandherbland is also present between mangrovesand terrestrial forested vegetation.

Beach ridge and dune casuarina low woodlandand open forest is the most dominant woodyvegetation landward of strand herbland. Thedominant species is Casuarina equisetifoliavar. incana. It forms low woodlands and openforests seven to twelve metres high. Largeareas of C. equisetifolia var. incana, as seenbetween Slade Point and East Point, mayindicate recent coastal accretion and/or dunedisturbances. Beach ridge and dune casuarinavegetation with beach scrub elements isusually found behind both exposed andprotected beaches. However, north of East Point,a large area of C. equisetifolia var. incanaopen forest occurs with beach scrub elements.

Freshwater swamp with treeless herblandAquatic treeless herblands include swampgrasslands, swamp sedgelands and openwater herblands. A total of 104 plant species,including 85 native species (82 percent), wererecorded from treeless freshwater wetlands.The flora includes emergent grasses, rushesand sedges frequently found in shallow waterand/or wetland edges. The deeper and openwater areas support many floating submergentaquatic plants.

Freshwater swamp with melaleucaopen forest and woodlandThe melaleuca open forests and woodlandsof the Mackay Coast are among the moresignificant native wetland vegetation typesfound within the study area. These wetlandforests support 193 native (63 percent) and113 introduced (37 percent) vascular plants.

Melaleuca leucadendra open forests areparticularly important and are found in low-lying coastal areas at Slade Point, Far Beachand McEwens Beach (locally known asMcEwans Beach). M. leucadendra dominatesthis forest type, forming a mid-dense canopy18–30m tall, often as monospecific stands.The secondary canopy and shrub layer ispoorly developed and groundcover is sparse.

Melaleuca dealbata open forests occur oncoastal beach ridges of low relief on sandysoils at Shoal Point and Dunrock, and nearDudgeon Point. These sites are considerablydrier than those found with M. leucadendraopen forest. The canopy is mid-dense, 15 to25m high, and dominated by M. dealbatawith occasional eucalypt species such asEucalyptus platyphylla, E. tereticornis andCorymbia tessellaris growing on the raisedbeach ridges. The lower canopy is sparse, fourto twelve metres tall, and comprised mainlyof littoral rainforest species. The shrub tosmall tree layer and groundcover are sparse.

Melaleuca viridiflora low woodland to lowopen forest occurs as natural formations oras regrowth after clearing. The disturbedcommunities are easily identified bymonospecific stands of M. viridiflora.

Small areas of M. viridiflora low woodlandoccur on wet dune sandy soils near SladePoint. Larger areas of M. viridiflora openforest with emergent eucalypts occur on morefertile coastal plains soil such as those foundnear Slade Point and near Mount Hector.

Riparian forestRiparian forests occur along the majority ofthe creeks in the study area as well as alongthe Pioneer River. Specialist riparian plantspecies also occur, such as Casuarinacunninghamiana subsp. cunninghamiana.Some mangrove species are included asriparian as they provide a transitional zonebetween tidal marine channels and drylandvegetation.

Riparian forests are the second mostdiverse assemblage in the study area, with309 (71 percent) native and 127 (29 percent)introduced species. The high speciesrichness of riparian forests results from thecombination of aquatic, wetland, dryland,rainforest and open forest species growingwithin one ecosystem.

Estuary riparian forests occur on the lowerreaches of tidal waterways. The intertidalmargins support mangrove low closed forestfour to twelve metres tall. The low estuarybanks are typically sandy beach ridgesand/or a coastal plain consisting of a mixtureof alluvium sand and gravel. Melaleuca/eucalypt open forest up to 18m tall occurslandward of the mangroves.

Tidal mid-reaches riparian forest occurs inmost creeks within the study area becausethe tidal range is large. The tidal limits vary,extending between two and eight km inlandfrom estuarine areas. A narrow mangrovefringe occurs in the middle reaches. Adjoiningthis zone are eucalypt open forests up to25m tall.

Freshwater mid-reach riparian forest occurs onlevee banks at Reliance, Bakers and LouisaCreeks. The zonation pattern includes awetland vegetation zone, a gallery rainforestzone and a eucalypt open forest zone.

Much of the freshwater upper-reach riparianforest vegetation type occurs inland, outsidethe 5km wide coastal study strip. It includesmixed-gallery open forest in creek beds andlower-terrace slopes and eucalypt openforest on upper-terrace slopes.


Mangroves in McReady’s Creek

Lowland littoral rainforestMost of the lowland littoral rainforests thatoccur on fertile alluvial soil in the Mackayregion have been cleared for sugarcanecultivation. Two small areas of lowlandlittoral rainforest remain along the middlereaches of Reliance Creek and the uppermiddle reaches of Louisa Creek (nearTimberlands). These areas have a largenumber of native species (226) and arerelatively weed-free.

Hill and headland rainforestHill and headland rainforest occurs as small,isolated fragments on slopes or on well-developed headland soils. Rainforestpatches occur on Mount Bassett, on hillsnear the Blacks Beach area, and onheadlands at Dolphin Heads and Eimeo.Despite the small size, hillside and headlandrainforest has a high native diversity (209species) and a very low proportion ofintroduced species (seven).

Hill, headland, lowland and dune eucalypt open forestEucalypt open forests are found on a varietyof soils and topography along the MackayCoast, from dune systems and well-developed alluvial soils to rocky substrates.The eucalypt open forest complex of theMackay coast is the most diverse nativevegetation type found within the study area.It supports 356 (70 percent) native and 152(30 percent) introduced vascular plants.

Eucalypt open forests dominated byCorymbia tessellaris are most often found insandy soils of alluvial plains and beach ridgesystems landward of coastal Casuarinaequisetifolia var. incana.

C. tessellaris open forest with beach scrubunderstorey is closely associated withcoastal areas and sandy substrates, usuallyfound landward of the casuarina woodlandzone at Bucasia, Shoal Point, Blacks Beach,Slade Point, Andergrove, Far Beach andBakers Creek.

Open forest characterised by thepredominance of Eucalyptus crebra in themid to upper layers of the formation occurson hillsides and undulating areas, such asrocky skeletal soils. The majority of this foresttype is found around the Hay Point–MountHector area and near Louisa Creek.

The eucalypt open forest associations of theMackay Coast may intergrade and form amixed unit. Mixed eucalypt open forestoccurs in stony soils mainly on low hills. Thismixed unit may adjoin E. crebra open forest.

Sandy seashore rainforest beach scrubBeach scrub consists of many rapidlygrowing rainforest species. Some 194(76 percent) native species have beenrecorded in this unit. This vegetationassociation is found in sheltered areaslandward of the casuarina zone.

Beach scrub varies from relatively simpledune open scrub of a few rainforest speciesto more complex, rich closed forests.Species-rich closed forest up to 16m talloccurs at Shoal Point, Harbour Beach, BlacksBeach and Hay Point.

Rocky shore vegetationRocky shores occur at Shoal Point, DolphinHeads, Slade Point, Lamberts Lookout,Mount Hector and Hay Point. Shinglebeaches associated with headlands occur atDolphin Heads and Lamberts Lookout. Theseaward sides of these headlands are sheerand the vegetation on lower slopes is sparseand/or windswept. Closed grassland andclosed herbland occur on the more exposedsections, with closed heaths and closedscrubs containing occasional emergents onless exposed sections. Species richness isvery high, with 197 (70 percent) nativespecies and 86 (30 percent) introducedspecies.

DisturbedAbout 70 percent of all native vegetation hasbeen cleared for sugarcane farming orresidential purposes. Natural vegetation hasalso been disturbed, destroyed or severelymodified by the establishment of pasture,small crop farming and other land usesincluding roads.


Dune vegetation on Bucasia Beach.

Dune vegetation zonationand managementTwo distinct zonation patterns can be observed:

� along the exposed coastline, such as atBucasia Beach and Harbour Beach. Thezonation sequence includes a beach zone,foredune area, and a hind dune and swalearea; and

� along the low-energy beach ridgecoastlines such as Slade Bay Beach, TownBeach and McEwens Beach. The zonationsequence includes a tidal flat area, beachzone and beach ridge zone, behind whichis an estuary zone.

Sandy shore stability and plant diversitydepend on the presence of specialisedseashore zonations. Most beaches along theMackay coast require all of the majorvegetation zones to maintain the specialistspecies required for natural beach stability.

In places such as Shoal Point Beach,northern parts of Blacks Beach and TownBeach, all strand vegetation has beeneroded. Native plants cannot perpetuatewhere the processes of active erosion, fire,trampling and grazing persist. For example,fire-sensitive Casuarina equisetifolia var.incana and beach scrub vegetation arefrequently replaced by open scrubs after anoutbreak of fire.

As a result there are many disturbed sectionsof the coast that do not show an idealisedzonation pattern. These areas are nowheavily infested with invasive plants such as Panicum maximum, Lantana camara var.camara, Psidium guajava, Agave vivipara,Opuntia stricta and Brachiaria mutica.

Weed managementWeed infestation is a major factor affectingthe native vegetation of the Mackay coast,and the control of these weeds requiresactive management. Within the Mackay studyarea, 310 species (28 percent) of the totalflora are naturalised exotics not native toAustralia. The area also has 56 species ofenvironmental weeds that are seriouslyinvasive.

The vegetation associations most susceptibleto weed invasions are sandy seashores,melaleuca forests, rocky seashores, eucalyptopen forests, riparian forests, beach scrub andfreshwater treeless herbland. The vegetationassociations that are relatively free of weedsinclude mangrove areas, hill and headlandrainforest and lowland littoral rainforest.

The infestation of environmental weeds isslightly different from the occurrence ofgeneralised weeds. Environmental weedsare more successful in riverine habitats.Moderately susceptible habitats are rockyshores, melaleuca swamps, sandy shores,beach scrubs and open forests. Habitats withlow susceptibility are saline flats, lowlandand hillside rainforests, and aquatic flats.Significant environmental weeds includeDalbergia sissoo, Syzygium cumini andPsidium guajava.

The presence of weeds alters the naturalzonation patterns present in the Mackayarea. For example, Panicum maximum andLantana camara var. camara affect naturalprocesses along Mackay’s sandy seashores,especially in the Casuarina equisetifolia var.incana woodlands. When fires are lit, the fuelbuilt up by Panicum maximum and Lantanacamara var. camara causes hot fires thatdamage and effectively replace the fire-sensitive species C. equisetifolia var. incana.Natural establishment of tree seedlings istherefore retarded in dune areas degraded bydense covers of these weeds.


Vegetation conservationThe majority of remaining vegetation typescould be preserved by incorporatingrelatively small areas of high habitat diversityin a series of green corridors. These corridorswould be shaped as a ‘T-square’incorporating a coastal strip and a riparianzone. The coastal zone preservation areascould include Slade Bay, Sandringham Bayand Dalrymple Bay T-square green corridors.

Collectively, these proposed terrestrialconservation areas cover less than fourpercent (about 1100ha) of the total studyarea. However, the areas include most of theremaining lowland and seashore vegetationtypes. These green corridors include about75 percent of all locally endangered plants.

At least four important coastal sites lie withinthe mapped area.

1. Louisa Creek gallery forest and estuary.This site supports gallery forest andlowland closed forest (at Timberlands)surrounded by sugarcane farming andurban development. Currently this species-rich vegetation is almost free of weeds.The lower banks of Louisa Creek andadjoining hillsides near Dudgeon Pointsupport important remnant stands ofcoastal eucalypt open forest. It should benoted that this site lies to the south of thestudy area.

2. Sandringham Bay–Bakers Creekaggregation. This wetland is listed as awetland of national importance. The areaincludes diverse wetland sites at McEwensBeach and Dudgeon Point. Sandy Creeksupports the only known coastal-zonepopulation of Eucalyptus ravertiana inQueensland.

3. Slade Bay corridor. This coastal siteenhances the outstanding landscapefeatures of Mackay City. The Slade Pointdune area and Mount Bassett rainforesthave high conservation values, and theunique Melaleuca leucadendra openforest has very high conservation value. Asubstantial portion of the proposed SladeBay T-square green corridor is alreadyproclaimed as the Slade Point Reserve forNatural Resource Management. Theincorporation of sites at McCreadys Creek,Andergrove, Slade Bay, Slade Point,Harbour Beach and Mount Bassett into alarge group will result in a more resilientand diverse unit for conservation.

4. Shoal Point corymbia/banksia dune openforest. The area covers about 10ha ofundisturbed Corymbia tessellaris andBanksia integrifolia open forest. Thiscommunity is rare and atypical of theentire study area.


Slade Bay and McReady’s Creek.

IntroductionA review of the fauna observed in the Mackaystudy area has been undertaken with anemphasis on commercially valuable, and rareand threatened species.

The following discussion is presented interms of major habitat types, which closelyfollow the vegetation associations. A summarymap showing the distribution of these habitattypes is given in figure 6. These habitats canbe represented by three broad categories:

� wetland habitats;

� terrestrial habitats; and

� marine habitats.

Fauna of wetland habitatsWetlands are a prominent feature of theMackay study area and the habitat includesbeaches, tidal flats, freshwater swamps,saline flats and estuaries.

The extensive wetland around SandringhamBay and Bakers Creek has been listed as awetland of national importance because itis an example of a marine and estuarinewetland in the Central Queensland Coastbioregion (Sattler and Williams 1999). It issignificant because of the extensive expanseof intertidal and shallow-water habitat, thediversity of the shoreline and the extent ofthe mangroves. It is recognised as anationally-important area for shorebirds.

The terrestrial wetlands of the study area,which include mangroves and freshwaterswamps, are critical habitat for false water-rats. False water-rats, listed as vulnerable,have recently been rediscovered in theMackay study area.

These wetlands are also considered to be of national importance for shorebirds. TheMackay region has been ranked sixth outof 13 regions in Queensland in terms of thetotal number of shorebirds present. TheMackay area is of international significancefor the Mongolian plover, eastern curlew,great knot and sooty oystercatcher, and ofnational significance for the terek sandpiper,bar-tailed godwit and ruddy turnstone.

Wetlands in general, not only mangroveareas, are critical for many fisheries species.All tidal wetlands, including intertidal flatsand channels, sandbars, river banks andclaypans, contribute to ecosystem complexity,which enables fisheries resources to feed,grow and reproduce to complete their lifecycles.

These areas are important habitat for a numberof notable species including barramundi,grey mackerel, sea mullet, school mackerel,whiting, mud crab and tiger prawns.

BeachesThe Mackay area is characterised by anumber of wide sandy beaches. This habitattype includes sandy beaches and vegetatedforedunes. Beaches are inhabited by avariety of organisms that are often specialisedand usually restricted to this zone.

Shorebirds are the most conspicuous faunainhabiting these beaches. The beaches areparticularly important as high tide roostingsites. More than 1000 birds have beenrecorded roosting at high tide on Town Beachand Far Beach/Bakers Creek. Other importanthigh-tide roosting sites where more than300 birds have been recorded includeShoal Point, the Pioneer River mouth and anarea south of the study area aroundMcEwens Beach.

Notable species reliant on the beaches in thearea include eastern curlews, little terns,beach stone-curlews and flatback turtles.There are eight resident pairs of beach stone-curlews, and about 50 to 60 turtles nestannually on the beaches.

7 Fauna


Tidal flats and estuariesA gentle slope sheltered from the prevailingsouth-easterly waves, the presence of riverand creek entrances, and a large tidal rangecombine to form extensive intertidal sandflatsand mudflats. The most extensive areas arein Sandringham Bay, the area around themouth of Bakers Creek, and at Town Beachand Far Beach.

The tidal flats are important foraging habitatfor the large number of shorebirds thatcongregate in the area. Extensive estuarineareas occur around the entrances to AlligatorCreek, Bakers Creek, Pioneer River andReliance Creek.

Estuaries are the meeting place of salt andfresh waters. Rich in nutrients, they areimportant habitats for adult marine animalsand critical nursery habitat for the juvenilesof many species. Notable species reliant onthese estuaries include barramundi, mullet,eastern king prawns, banana prawns, crabs(mud and sand) and mackerel (school and grey).

Freshwater swampsFreshwater swamps scattered throughout thearea include areas of treeless swamps andmelaleuca swamps. There are freshwaterswamps at Shoal Point and Slade Point.

These swamps are characterised by seasonalperiods of inundation and are an importantseasonal habitat for a variety of organismsincluding wading birds. They are importantfeeding areas, and during periods ofinclement weather are important roostingsites. Notable species reliant on thesefreshwater swamps include the black-neckedstork and radjah shelduck.

Saline flatsSaline flats include intertidal herblands andmangrove areas. Extensive tracts are foundaround Reliance Creek, Slade Bay, BakersCreek, Sandringham Bay and in the BassettBasin around the Pioneer River.

The ecological values of saline flats havebeen well documented; they are ecologicallyhighly productive, are important habitatsfor adult marine animals, and are criticalhabitat for juveniles of many marine species.Notable species that are dependent on thesemangroves to complete their life cycle includebarramundi, mud crab and banana prawn.

Bassett Basin is particularly important forbarramundi as the freshwater ponds thatflow into it create a unique tidal habitat.Other notable species that are dependent onsaline flats include estuarine crocodiles.

Fauna of terrestrial habitatsThe terrestrial habitats of the Mackay studyarea are dominated by the town of Mackayand the surrounding sugarcane farms.

Open forestsMost of the open forests found in the Mackayarea are small, fragmented, remnant patches.The most extensive remnant block is behindDudgeon Point. A large number of themammals, birds, reptiles and amphibiansfound here are reliant on open forests asimportant foraging and nesting habitat. Nonotable species are known to be reliant onthese open forests.

RainforestsIsolated remnant rainforest patches occuraround Reliance Creek, Louisa Creek, MountBassett, Blacks Beach and Dolphin Heads.A few strips of littoral rainforest occur alongBakers Creek, Louisa Creek, Reliance Creek,Leila Creek and Sandy Creek. Patches ofbeach scrub are dotted throughout some ofthe open forest and foredune areas. Theseoccur behind McEwens Beach, Bakers Creek,Lamberts Beach, Harbour Beach, BlacksBeach and Bucasia.

The rainforests of the study area are smalland fragmented. They are not likely to belarge enough to harbour any significantpopulations of rainforest specialists. Theyare, however, important temporary habitat fora wide variety of generalist species that movefrom one area to another. They are used byrainforest specialists such as Torresianimperial-pigeons that feed in these areas asthey migrate up and down the coast. Nonotable species are known to be reliant onthese rainforests.

Rocky headlandsThe study area’s numerous rocky headlandsinclude Shoal Point, Eimeo, Dolphin Headsand Slade Point. Rocky shore habitatssupport a wide variety of specialised fauna.Sooty oystercatchers, which are occasionallyseen in the area, are a notable speciesusually associated with rocky shores.


Tidal flats are important foraging habitat for migratory shore birds.

Fauna of marine habitatsThe tidal flats and estuaries of the area giveway to a gently sloping ocean floor. A fewreefs and moderate seagrass beds occur inthe inshore waters. Flat Top and Round TopIslands are small continental islands justeast of Mackay. The Great Barrier Reef liesapproximately 180km east.

Operating within the Mackay study area are atrawl fishery, a tropical inshore finfish fishery,a crab fishery and a limited reef-line fishery.During the period from 1994–95 to 1997–98,the commercial fishing industry harvested onaverage 108t per annum of fisheries resourcesfrom the region. The main species harvestedwere king prawn, shark, banana prawn, crab,mackerel, mullet, bug, and barramundi.

OceansOceanic waters are important habitat for avariety of pelagic and benthic species.Commercial species dependent on thesewaters include king prawns, banana prawns,crabs (sand and mud), bugs, mackerel, sharkand mullet. Other notable fauna that frequentthe oceanic waters of the study area includeIrrawaddy dolphins and humpback whales.

ReefsReefs are present at Dudgeon Point, OysterRock, Flat Top Island, Dangerous Reef, SladeIslet, Slade Rock and around Shoal Point.They comprise rocky reefs and coral reefs.Rocky reefs attract a wide variety of marineanimals because they are a prominentfeature in an otherwise featureless marineenvironment, and coral reefs are well knownfor their diversity. Notable species reliant onthese reefs include red-spot king prawns,loggerhead turtles and flatback turtles.

Seagrass bedsSmall beds of seagrass occur at Round TopIsland, Flat Top Island and Slade Point.Seagrass beds are ecologically importantbecause they are highly productive, theytrap and stabilise coastal sediment, and theyare critical habitat for a number ofcommercial and protected species includingbanana prawns, tiger prawns, dugongs andgreen turtles.

Fauna and habitatconservationWithin the Mackay study area are a numberof protected areas including fish habitatreserves at Sand Bay and Bassett Basin,Bakers Creek Conservation Park, and theSlade Point Reserve for Natural ResourceManagement.

It has long been recognised that thepreservation of biodiversity requires thedevelopment of a comprehensive andrepresentative system of protected areas. Toachieve this goal, the assessment, planningand management of protected areas must beundertaken in a bioregional context.

Regional ecosystems are the primary unit forthe development of a comprehensive andrepresentative system of protected areas. Itis thought that the identification andadequate preservation of a representativesample of the different regional ecosystemswill ensure that biodiversity is maintained.

The Mackay study area lies within the CentralQueensland Coast bioregion, which is centredon the high-rainfall coastal lowlands, hillsand ranges around Mackay. Ten regionalecosystems occur in the Mackay study area(Sattler and Williams 1999, Ball 1998). Threeof these ecosystems are classified asendangered and three are classified as of concern.

The endangered regional ecosystems thatoccur in the area are freshwater swamps,Corymbia intermedia-Eucalyptus platyphyllawoodland and Eucalyptus tereticornis grassywoodland.

The usefulness of the regional approach toidentifying and managing protected areaswithin the study area is limited because mostof the remnant vegetation associations occuras small, fragmented areas. However,extensive areas of freshwater swamps occurthroughout the study area.

The use of regional ecosystems is notappropriate for all species. This approachdoes not address the conservation needs ofspecies that are rare and threatened, or havepatchy distributions. Planning for theconservation of biodiversity should alsoinclude other complementary strategiesfocusing on the specific requirements of theparticular species of concern.

Seventeen species listed in the QueenslandNature Conservation Act 1994 have beenrecorded from the Mackay study area. Thearea is particularly important for flatbackturtles, beach stone-curlews, eastern curlewsand false water-rats. These species arereliant on the wetlands, particularly themangroves, freshwater swamps, beaches andtidal flats of the Mackay study area.


A significant number of turtles nest annually on the beaches in the Mackay Region.

IntroductionPhysical coastal processes in the Mackayregion are directly affected by meteorologicalconditions. The dominant east to south-easterly trade winds have an important effecton wave conditions and are primarilyresponsible for the formation of sand dunes.Rainfall in coastal catchments has animportant bearing on fluvial sedimentsupply, along with the growth of vegetation.

The most significant meteorological eventsoccurring in the region are tropical cyclones.

Cyclones and tropical lows generate extremeconditions of wind, waves and water levels,and are often responsible for storm surgesand high rainfall leading to flooding andshort-term beach erosion.

Variability in the climate influences seasonalconditions. The three most dominant formsof variability affecting coastal Queenslandare the El Niño/Southern Oscillation (ENSO),the Inter-decadal Pacific Oscillation (IPO) andgreenhouse-induced climate change.

A review of the region’s meteorology has beenundertaken, primarily using temperature,rainfall, wind and miscellaneous climate datafrom the Bureau of Meteorology. TheQueensland Department of NaturalResources supplied stream gauging data forthe Pioneer River and tropical cyclone datawere from Lourensz (1981) and the Bureau of Meteorology (figure 7 shows the Mackayregion and the locations of the various land-based data monitoring sites).

8 Meteorology


Figure 7 Land–based monitoring sites: Pioneer River, Bakers Creek and Sandy Creek catchments and average annual rainfall isohyets (mm)

Climatic summaryThe climate of the Mackay region is stronglyinfluenced by the subtropical ridge of highpressure generally located to the south of theAustralian continent. Cells of high pressurecreate an anticlockwise circulation resultingin a moist onshore flow of air, known astrade winds, which occur throughout theyear. In winter, the ridge of high pressure istypically centred around 30°S and minimumrainfall conditions are experienced. Insummer, high pressure systems are typicallycentred around 40°S. The onshore windshave a longer passage over warmer seas,resulting in a high moisture content of the airmass and higher rainfall. Synoptic patternsreflecting these typical conditions are shownin figures 8 and 9.

Near the coast, the local wind regime isaffected by the sea breeze. The strength ofthe sea breeze is determined by themagnitude of the temperature differencebetween the land and the sea, and isgenerally greatest in the spring and earlysummer months, peaking in mid-afternoon.The direction of the sea breeze isapproximately normal to the generalcoastline orientation, north-easterly in thecase of the Mackay region. Wind is discussedin more detail elsewhere in this chapter.

In the summer months, tropical cyclones andtropical lows can exert considerableinfluence on northern Queensland weatherpatterns. These systems often interact withregions of high pressure over southernAustralia to produce strong pressuregradients over the whole of eastern Australia.The Mackay region is too far south to beregularly affected by the north-westmonsoon.

Average summer temperatures for Mackayrange from a minimum of 22 degrees to amaximum of 30 degrees and average winterdaily temperatures range from 11 degrees to24 degrees. The maximum recordedtemperature at Mackay (Mount Bassett) is39.4 degrees and the minimum recordedtemperature is 3.8 degrees. The temperaturerange generally increases with distance fromthe coast, primarily due to the cooling effectof sea breezes.

Humidity, unlike temperature, tends todecrease with distance from the coast.Highest values of humidity occur in themornings of the late summer months (forexample, the average level of 9 a.m. humidityin May is 82 percent). The minimum humidityfalls to about 54 percent in August andSeptember. The average humidity variesduring the day, due mainly to the influence ofthe sea breeze (table 6 shows temperatureand humidity data for the Mackay region).

Evaporation rates, linked to temperature andhumidity, tend to be highest aroundNovember in the Mackay region, with a7.8mm/day average. The lowest rates aretypically in June, with a 3.4mm/day average.Locations further inland have higherevaporation rates than coastal areas(evaporation data are shown in table 7).


Figure 8 Typical synoptic pattern, winter (30 June 1991)

Figure 9 Typical synoptic pattern, summer (3 January 1991)


Table 6 Monthly and annual temperature and humidity statistics for Mackay in °C

Station Years of record J F M A M J J A S O N D Annual

Mackay (Mount Bassett) Elevation 30.2m AHD 1959 to 1996

Mean maximum 37 30.0 29.5 28.5 26.6 24.1 21.9 21.2 22.4 25.0 27.4 29.1 29.9 26.3

Highest maximum 37 37.2 38.7 34.7 33.8 29.2 29.1 29.7 29.3 32.2 34.9 34.9 39.4 39.4

Mean days >30°C 37 15.7 10.5 4.7 0.6 0.0 0.0 0.0 0.0 0.3 2.1 8.6 14.8 57.3

Mean minimum 37 23.4 23.2 22.1 20.0 17.1 13.7 12.7 13.9 16.5 19.5 21.8 22.9 18.9

Lowest minimum 37 17.2 17.8 13.1 12.0 7.1 4.6 3.8 5.0 7.9 10.6 14.9 15.3 3.8

Mean days <2°C 37 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

HumidityMean 9 a.m.:

air temp. °C 37 27.3 26.8 25.8 23.7 20.8 17.7 16.9 18.7 22.0 24.9 26.6 27.4 23.2

wet-bulb temp. °C 36 24.0 24.0 23.1 21.3 18.6 15.4 14.5 15.9 18.3 20.5 22.3 23.4 20.1

dew point temp. °C 36 22.3 22.6 21.6 19.8 16.9 13.3 12.3 13.4 15.4 17.7 19.9 21.3 18.1

relative humidity % 43 75 79 78 80 80 77 76 74 68 66 67 70 74

Mean 3 p.m.:

air temp. °C 45 28.6 28.3 27.5 25.8 23.4 21.2 20.4 21.4 23.6 25.9 27.5 28.5 25.1

wet-bulb temp. °C 45 24.5 24.6 23.7 22.1 19.9 17.4 16.7 17.6 19.2 21.1 22.8 23.8 21.1

dew point temp. °C 36 22.4 22.8 21.7 20.0 17.7 14.5 13.7 14.7 16.3 18.2 20.4 21.6 18.7


Mackay (Post Office) Elevation 11.0m AHD 1870 to 1987

Mean maximum 49 30.3 29.8 29.0 27.3 24.7 22.6 21.9 23.0 25.2 27.5 29.0 30.2 26.7

Highest maximum N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A

Mean days >30°C N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A

Mean minimum 50 23.3 23.1 22.0 19.4 16.1 13.4 11.7 12.5 15.4 18.6 20.8 22.5 18.3

Lowest minimum N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A

Mean days <2°C N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A

Mackay (Te Kowai) Elevation 13.7m AHD 1889 to 1996

Mean maximum 69 30.9 30.3 29.5 28.0 25.7 23.7 23.3 24.6 26.7 28.8 30.4 31.3 27.7

Highest maximum 25 40.5 38.1 37.8 33.9 30.5 30.0 29.0 35.8 34.7 36.0 38.9 38.0 40.5

Mean days >30°C 21 17.4 11.0 8.3 2.5 0.1 0.0 0.0 0.4 1.9 5.0 12.9 15.6 75.2

Mean minimum 68 21.8 21.8 20.7 17.9 14.5 11.7 10.2 10.9 13.5 16.6 19.2 20.9 16.5

Lowest minimum 25 16.7 17.2 10.8 8.0 3.3 1.5 0.5 1.5 5.0 6.1 12.5 15.0 0.5

Mean days <2°C 20 0.0 0.0 0.0 0.0 0.0 0.1 0.4 0.0 0.0 0.0 0.0 0.0 0.5

HumidityMean 9 a.m.:

air temp. °C 68 27.8 27.0 26.1 24.0 21.0 18.3 17.6 19.4 22.7 25.7 27.5 28.3 23.7

wet-bulb temp. °C 67 24.3 24.2 23.4 21.4 18.6 16.0 15.2 16.3 18.6 20.9 22.4 23.7 20.3

dew point temp. °C 19 22.4 22.6 21.8 19.9 17.3 14.1 12.8 13.7 14.8 17.4 19.3 21.0 17.7


Mean 3 p.m.:

air temp. °C 10 29.2 28.3 28.0 26.4 24.0 22.3 21.8 23.0 24.9 26.6 28.0 29.8 25.7

wet-bulb temp. °C 10 24.4 24.4 23.5 22.2 19.6 17.6 16.6 17.3 18.8 20.7 22.1 25.2 20.4

dew point temp. °C 11 21.7 21.9 21.1 19.0 16.4 13.7 12.2 12.8 14.5 17.1 18.9 N/A 17.0


Table 7 Mean daily evaporation (mm) for Mackay region 1889 to 1996

Station Years of record J F M A M J J A S O N D Annual

Mackay (Te Kowai) 20 7.1 6.1 5.7 4.8 3.7 3.4 3.5 4.5 6.0 7.3 7.8 7.5 5.5

Rainfall and hydrologyRainfall within the Mackay region is highlyvariable and has a marked seasonality.Seasonal variations are due mainly to theprocesses associated with the migration of thesubtropical ridge and the input from tropicallow pressure systems (monthly rainfall averagesfor selected recording stations within theregion are given in table 8).

Approximately 70 percent of the annualrainfall is recorded in the four-month periodfrom December to March. The meteorologicalsystems that influence this seasonal deluge are:

� tropical cyclones and rain depressions;

� upper troughs, with easterly inflowing winds;

� upper troughs and middle latitude frontsoccurring in westerly winds; and

� convectional instability developing insouth-easterly air streams, which mainlyinfluence the coastal section.

Thunderstorms contribute greatly to monthlyrainfall totals. The Department of NationalDevelopment (1965) estimated that 70 to 80percent of all September to December rainfallresults from thunderstorm activity.

Annual rainfall totals are quite variable in theregion. Throughout eastern Queensland,rainfall has a strong association with theSouthern Oscillation and can explain as muchas 40 percent of the rainfall variance (Partridge(ed.) 1994). Differences in air pressurebetween the regions of Darwin and Tahiti area measure of the strength of the Southern

Oscillation. When the Southern OscillationIndex is strongly positive, cyclone genesis andthe subsequent paths are closer to the northernQueensland coast. Additionally, trade windsare stronger, resulting in a higher delivery ofmoist air and above-average rainfall.

Due to the very high proportion of annualrainfall occurring during the summer months,the failure of summer rains has historicallyled to drought conditions. The worst droughton record occurred during the period 1900 to1903. Successive summer rains failed,leading to heavy stock and crop losses andflow in the Pioneer River was interrupted.Conditions of below-average rainfall leadingto drought or semi-drought were recorded inthe periods 1911 to 1916, 1918 to 1920, 1922to 1926, 1930 to 1933, 1943 to 1949, 1951to 1952, 1965, 1982 and 1992 to 1995.

The coastal topography has an importanteffect on the local meteorology. The ruggedClarke, Connor and Denham Ranges risesharply from the coastal plains to elevationsin excess of 1250m. In the immediate regionof Mackay the onshore trade winds aredeflected upwards (this is known as orographicuplift) as they approach the mountain rangesclose to the coast, and this can result in heavyrainfall (figure 7 shows the distribution ofaverage annual rainfall and clearly showsthat the highest concentration of rainfallwithin the region is around Eungella on theClarke Range). The amount of rainfall generallydecreases with elevation but also increasesimmediately adjacent to the coastline.

The lowest monthly rainfall generally occursin September. The distribution of theSeptember average rainfall is quite differentfrom the annual distribution. The maximumaverage rainfall recorded is not at an inlandlocation but in Mackay.

The most intense rainfall recorded in theregion occurred during the February 1958rain depression. The Bureau of Meteorology(1965) reported that, at Finch Hatton, the 24-hour total for this event reached 878mm,Australia’s second highest 24-hour rainfalltotal. Approximately 530mm of this rainfallwas recorded over a five-hour period.

Flooding within the Mackay region occurspredominantly in summer and tends to be theresult of high rainfall from tropical cyclonesor rain depressions. The floods resulting fromthe February 1958 event caused widespreaddevastation, and bridges were completelywashed away in neighbouring catchments. ThePioneer River at Mirani reached a record heightof 52ft 10in (15.85m water depth) duringthis event (Bureau of Meteorology 1965).

Another extreme event captured on recordresulted from rainfall associated with thedevastating January 1918 cyclone. A total of1411mm was recorded between 22 to 24January 1918. The Pioneer River at Miranipeaked at a water depth of 14.1m (Bureau ofMeteorology 1965). This event also causedflooding of rivers along the coast from Gladstoneto Townsville (highest and lowest annualrainfall data within the Mackay region areshown in table 9).


Table 8 Average monthly and annual rainfall for Mackay region stations (mm) for 1870 to 1996

Station Years Annual J F M A M J J A S O N D Annualof record rain days

Blue Mountain 40 N/A 209 220 149 60 36 54 38 17 25 42 65 131 1046

Dalrymple Heights 60 N/A 380 481 380 208 137 98 79 69 33 65 95 202 2220

Doraville 8 N/A 241 307 97 39 51 28 16 68 20 41 75 269 1113

Eton 40 N/A 326 288 226 85 53 47 35 22 22 42 67 150 1363

Farleigh Mill 40 N/A 397 383 317 160 103 75 39 29 35 47 74 162 1821

Finch Hatton 84 86 312 374 270 128 83 65 46 40 30 48 86 174 1653

Gargett 40 N/A 292 326 260 92 70 58 52 34 25 40 83 146 1478

Kuttabul 40 N/A 474 379 309 111 66 56 37 21 13 58 75 162 1761

Mackay (Mount Bassett) 37 129 298 306 281 148 113 61 44 29 14 38 86 193 1608

Mackay (Post Office) 80 110 335 318 308 152 94 68 41 26 40 46 74 164 1665

Mackay (Te Kowai) 107 118 353 347 289 141 93 61 37 28 29 45 79 183 1684

Mirani 27 N/A 265 336 219 112 92 41 38 35 22 53 98 193 1496

Mount Charlton 44 N/A 352 418 292 142 101 50 34 36 20 57 106 215 1826

Netherdale 40 N/A 339 321 267 115 66 94 50 33 34 46 70 152 1587

Pleystowe 40 N/A 377 349 299 128 77 58 41 33 35 49 78 152 1676

Sarina 88 105 379 396 295 131 81 56 39 31 26 56 106 201 1804

Walkerston 40 N/A 364 341 270 129 74 57 37 25 29 44 76 154 1600

Figure 10 shows a summary of flood peakdischarges for the Pioneer River at Mirani forflows greater than 500m3/s to the end of1999. Flood flows corresponding to majorrainfall events have been highlighted.

Mackay (Mount Bassett) is the official Bureauof Meteorology station for the region and hasoperated continuously since the closure ofthe aerodrome station in 1959. The Mackaywind recorder is situated close to the coast(Harbour Beach) but its location relative toMount Bassett affects recordings from thesouth-west to north-west sectors. Exposureto the east is excellent, but topographicacceleration effects result in an overstatementrelative to the offshore wind climate.

The predominant wind direction is the south-easterly trade winds, and this is reflected in thewind roses for Mackay (as shown in figure

11). The wind roses also show the effect ofthe north-easterly sea breeze, which isparticularly noticeable in the afternoonsduring summer and spring months.

During autumn and winter, the passage ofcold fronts embedded in the subtropical highpressure zone can result in periods of southerlyand south-westerly winds. During theafternoons, the sea breeze influence causesa greater occurrence of winds from the south-easterly sector.Most extreme wind events inthe region are associated with tropicalcyclones. Tropical cyclone Kerry produced thehighest recorded wind gust for the Mackayregion. Wind gusts are in the order of 1.5times greater than the average 10-minutewind speed. Recorded at 8.30am, 1 March1979, the easterly wind peaked at 141km/h.Extensive wind damage associated with

tropical cyclone Kerry was reported fromSarina to just north of Mackay. It is probablethat much stronger winds could haveoccurred during tropical cyclones beforeinstrumentation was installed.


Figure 10 Pioneer River peak flood discharge data at Mirani

Figure 11 Mackay (Mount Bassett) wind roses

Table 9 Highest and lowest annual rainfall values

Station Highest annual Lowest annual rainfall (mm) rainfall (mm)

Dalrymple Heights 4351 893

Doraville 2268 610

Finch Hatton 3581 603

Mackay (Te Kowai) 3455 632

Mirani 3078 509

Mount Charlton 3818 669

Sarina 3428 848

Tropical cyclonesA tropical cyclone can be described as anintense low pressure systems which formover warm ocean waters at low latitudes. Inthe southern hemisphere the horizontal windcirculation of a tropical cyclone rotates in aclockwise direction, as viewed from space.

For a weather system to be classified as atropical cyclone, the central pressure must bebelow 1,000hPa and 10-minute mean windspeeds must exceed 63km/h (gale force). TheBureau of Meteorology categorises tropicalcyclones according to the strongest windgust (specified in table 10).

Tropical cyclones affecting the Mackay regionare usually generated in the Coral Sea. Severalenvironmental conditions must be met for atropical cyclone to form (Gray 1968, 1979):

� warm ocean waters (of at least 26.5 degrees)throughout a depth of approximately 50m;

� an unstable atmosphere, conducive todevelopment of widespread thunderstormactivity;

� a minimum distance of at least 500kmfrom the equator, to provide sufficientCoriolis force;

� a pre-existing near-surface disturbancewith sufficient vorticity and convergence(tropical cyclones cannot be generatedspontaneously); and

� low values (less than about 10m/s) ofvertical wind shear between the surfaceand the upper troposphere.

Between November and April is generallyregarded as the tropical cyclone season. TheBureau of Meteorology has compiled a data-base of all tropical cyclones in the Queenslandregion for the period from July 1909 to April

1995. Only six tropical cyclones crossed thecoastline within 50km of Mackay City duringthis period and all occurred in the first half ofthe century (table 11 provides details ofthese events and figure 12 shows the tracksfor major tropical cyclones that have affectedthe Mackay coast).

Proh and Gourlay (1997) examined theoccurrence of tropical cyclones in theQueensland region using Bureau ofMeteorology data. Their data were re-analysedusing a different statistical method (figure 13provides the distribution of the averageannual occurrences for all cyclones in theperiod 1959 to 1996). It highlights theexpected high incidence of these events inthe Mackay region.

The region can be influenced by cycloneevents that do not necessarily cross the coastin close proximity. On Christmas Eve 1971,tropical cyclone Althea crossed the coastadjacent to Townsville, approximately 325kmnorth-west of Mackay, causing noticeableimpacts. Similarly, although tropical cycloneKerry did not pass over the Mackay region, itwas still significant enough to cause recordwind gusts.

The most significant tropical cyclone to affectthe Mackay region since 1909 occurred in1918, when an unnamed cyclone crossedthe coast at approximately 7.30am onMonday, 21 January. Early that morning, thebarometer on Flat Top Island had steadilydropped to 948hPa, until the needle restedon the rim of the barometer and was unableto record any lower readings. In Mackay, thewind swung from south to east to north atthe height of the cyclone, indicating that theeye passed slightly to the north of the town.The official pressure recording was 933hPa(Mackay Post Office) however, the pen of thebarogram had rested on the flange at thelower end of its limit for half an hour.

The cyclone had a devastating impact onMackay. A storm surge of 3.7m accompaniedthe cyclone. Over the period 22 to 24January, 1411mm of rainfall was recorded,resulting in an estimated peak flood dischargeof more than 9800m3/s in the Pioneer River.


Table 11 Tropical cyclones that crossed thecoast within 50km of Mackay City

Date Central pressure (hPa) Category

26 December 1916 985 1

15 December 1917 996 1

21 January 1918 933 4

27 February 1929 985 2

18 March 1940 987 1

8 February 1949 994 1

Figure 12 Tropical cyclone tracks impacting the Mackay region

Table 10 Tropical cyclone severity categories

Category Strongest gust (km/h)

1 <125

2 125–170

3 170–225

4 225–280

5 >280

As a result of the cyclone, 31 people perishedand property damage was estimated at£1million (1918 value). Residents reportedthat wind caused most of the damage toproperty, but nearly all fatalities resultedfrom the impact of the storm tide.

Climate variability

The climate fluctuation known as El Niño/Southern Oscillation (ENSO) is the mostprominent form of climate variability acrossthe Indo-Pacific region. In northern Australiait has a statistically significant impact onrainfall and other weather elements includingtropical cyclones (Nicholls 1992; Nicholls etal. 1998; Callaghan and Power, submitted).

The phenomenon is closely coupled withcharacteristic changes in upper oceantemperature patterns across the tropicalPacific Ocean. The period of the ENSO cyclevaries from a season or two to a few years.

The El Niño/Southern Oscillation is commonlydescribed by the Southern Oscillation Index(SOI). The El Niño phase (corresponding tonegative SOI) is characterised on a statisticalbasis by lower rainfall and fewer tropicalcyclones near the Queensland coast. Upperocean temperatures are typically lower aroundnorthern Australia and warmer in the EquatorialCentral to Eastern Pacific. The opposite LaNiña phase is characterised by higher rainfall,larger numbers of tropical cyclones and morewind. Upper ocean temperatures are generallywarmer around northern Australia and lowerin the Equatorial Central to Eastern Pacific.

It is important to understand that every ENSOevent is different, and the statistically moreprobable variations do not occur over everyregion during every event (figure 14 showsthe cumulative trend in monthly SOI since1957). It is evident that the overall trend wasdominated by El Niño events from the mid-1970s to mid-1998.

Recently, Power et al. (1999) highlighted thepotential importance for the Australian climateof a long-term cycle of sea temperatures inthe Pacific Ocean. This cycle is thought to belinked with changes in the slow, large-scalethermo-haline circulation of the Pacific Ocean.The oscillation is known as the Inter-decadalPacific Oscillation (IPO), and it occurs on timescales of 10 to 30 years or so. It also appearsto have a modulating effect on the way thatENSO events evolve. Callaghan and Power(submitted) describe a possible modulatingeffect of the IPO on tropical cyclone activity,including evidence to suggest that damagingimpacts in Queensland are more likely duringthe negative or cooler Pacific phase of the IPO.


Figure 13 Annual average occurrence of tropical cyclones, 1959 to 1996 (based on Proh and Gourlay 1997)

Figure 14 Cumulative SOI data

Satellite photograph of TC “Kerry” in the Coral Sea,April 1979 (Source: Bureau of Meteorology)

Climate changeThe potential impact of global warmingarising from the enhanced greenhouse effecthas become a major scientific and socialissue in recent years. Greenhouse warmingoccurs when solar radiation absorbed by theearth is re-emitted as heat energy back intothe atmosphere, where it is partly trapped bygreenhouse gases. These gases then re-emitthe radiation in all directions, furtherwarming the atmosphere and the earth’ssurface. The process is a natural one; withoutthese gases, the earth’s surface would beapproximately 33 degrees cooler. However,human activities have markedly increasedthe level of greenhouse gases in theatmosphere. This is expected to raise globaltemperatures, leading to changed climates.

The World Meteorological Organization’s(WMO) December 1998 annual Statement onthe Global Climate indicated that, globally,the 1990s were the warmest decade sinceinstrumental measurement started in the1860s. Recent scientific evidence based onpre-instrumental proxy climate data, mostlyfrom sites in the northern hemisphere,indicate the 1990s were the warmest decadeand the 1900s the warmest century duringthe past 1000 years.

A global consensus report on climate changeis provided by the Intergovernmental Panelon Climate Change (IPCC) of the WMO andUnited Nations Environment Program (UNEP).It is updated approximately every five yearsfollowing an intensive review by hundredsof scientists. Although tropical cycloneshave apparently varied on a regional basisover decadal time scales, IPCC (1995) andHenderson-Sellars et al. (1998) highlightuncertainties in past records and thedifficulties in discerning any long-termtrends. Henderson-Sellars et al. (1998)indicate the possibility of a modest increasein the maximum potential intensities oftropical cyclones.


IntroductionThe Mackay coastal region is subject toconsiderable variation in water levels andwater flows caused by a number of majorinfluences. The daily astronomical tide, witha maximum range of more than 6m, has adominant effect and the outflow of thePioneer River has an important localisedeffect. Seasonal large-scale weather patterns,interspersed with tropical cyclones or otherstorm events, can also have a marked influenceon regional water levels and currents.

A detailed assessment of the hydrodynamicsof the region has been undertaken for thisstudy, including:

� a review of all available information andprevious studies;

� the acquisition of water level and currentdata throughout the study area, includingvertical current profiling; and

� numerical hydrodynamic modelling of thetidal influence at both the regional scaleand local scale.

Mean sea-levelMean sea-levels are affected by geological(eustatic and tectonic) changes and potentialanthropogenic (human-induced) relatedimpacts. Although changes in the meansea-level occur very slowly, they are highlysignificant in the understanding of the coastalmorphology of the region. The characteristicsof a coastline comprised mainly of sandybeaches are highly responsive to changesin mean sea-level.

Over geological time scales, the Holoceneperiod (from 10,000 years BP) has featuredextensive variations in mean sea-level,primarily in response to global temperaturechanges. These changes have been a resultof the combination of specific sea (eustatic)and land (tectonic) movements, each relativeto the other. It is commonly accepted that thepresent sea-levels were reached approximately6500 years BP. Before this, during the mostrecent glacial period, sea-levels were in theorder of 160m below modern levels.

Following the relatively rapid post-glacialsea-level rise during the early Holocene,mean levels have been relatively stable atpresent levels.

There is evidence that the local sea-levelaround Mackay may have been as much astwo metres above modern levels around themid-Holocene (Hopley 1983; Masselink andLessa 1995). This is discussed further in thedescription of the geological history of theregion.

A review of modern sea-level records byGornitz and Lebedeff (1987) indicates a trendof about one to two mm/a rise in mean sea-level globally, attributed in this instance tonatural eustatic effects alone. The NationalTidal Facility (NTF) has undertaken an analysisof long-term sea-level observations at a numberof locations on the Australian coastline(PCTMSL 1999). The analysis indicates anoverall average of 0.3mm/a increase in meansea-level based on a network of 27 tidegauges with a minimum of 23 years of data.

Tidal records have been available in theMackay region since 1948 and, albeit withsome considerable gaps, exist in a digitisedform reaching back to 1960. The BeachProtection Authority’s storm tide gauge hasbeen operating in Mackay Harbour since1975. Assuming no tectonic contaminationof the record, an increasing trend of 1.24mm/ahas been determined by the NTF for 24.3years of data (PCTMSL 1999).

Anthropogenic changes due to the greenhouseeffect may also be capable of raising coastalwater levels by a further 0.2 to 0.9m over thenext 100 years if expected climate change

trends are not reversed. There is indisputableevidence that levels of greenhouse activegases such as water vapour, nitrous oxide,ozone and chlorofluorocarbons in theatmosphere have steadily increased sincethe industrial revolution, mainly due to theburning of fossil fuels.

One possible consequence of theseincreasing levels is a rise in the mean globaltemperature. As a result, anthropogenicallyinduced eustatic sea-level rise may alsooccur. While debate continues about thepossible natural feedback mechanisms thatmay be occurring to attenuate these effects,and continued efforts are made to reversethe trend in greenhouse emissions, it isprudent to consider the possible range ofimpacts such a sea-level rise might have ona coastal region such as Mackay.

Since greenhouse gas emissions depend onfuture human activity, predictions of theireffects cannot be made with certainty. TheUnited Nations International Panel on ClimateChange has developed a series of likelyscenarios, which are designed to investigatea range of possible climate impacts throughthe use of sophisticated numerical climatemodels (IPCC 1995). The current bestestimate is that sea-level will rise by 49cm bythe year 2100, with a range of uncertainty of20 to 86cm. Over a 50-year planning periodto 2050, the best estimate of greenhouse-related sea-level rise is 20cm (this scenariois shown in figure 15).

9 Water levels and currents


Figure 15 1990 to 2100 sea-level rise for scenario IS92a (after IPCC 1996)

Tides and tidal flowsThe Mackay region experiences some of thehighest astronomical tides in Australia,exceeded only by those of the north-westernAustralia coastline between Port Hedlandand Darwin. The large tide range results instrong tidal streams, often in excess of0.5m/s in some locations. In conjunctionwith the relatively flat beach profiles, a tidalexcursion of more than 2.5km is common insome areas, notably in the coastal sectionsouth of the Pioneer River entrance.

The gravitational attraction of the moon andthe sun combine to generate the tidalvariation in the world’s oceans. This variationis in the form of long-period waves, whichtravel through the ocean basins in complexpatterns dictated by the seabed topographyand the shape of the coastlines. In the south-western Pacific Ocean the main tide waveapproaches the Australian east coast from aneasterly direction.

In the Mackay region, the tide wave isconsiderably modified by the influence ofthe continental shelf and the Great BarrierReef. The tide is semi-diurnal (high wateroccurs twice daily) with a marked diurnal(daily) inequality.

The relatively shallow water of thecontinental shelf and the topography resultin a significant amplification, which reachesnear-resonance in the vicinity of Broadsound,to the south of Mackay. The mean springrange at Mackay is 4.56m and the range fromhighest to lowest astronomical tide is 6.41m.Strong tidal flows are driven by the variationin tidal characteristics along the coast.

The shallow water also causes a distortionand a noticeable asymmetry of the tide waveand associated tidal flows (figure 16 showsan extract of water level and current datarecorded at Oom Shoal 7km east of SladePoint and 9.9m depth).

The following characteristics are noted:

� there is a marked variation in successivehigh waters but little variation insuccessive low waters;

� the flood tide runs south towardsBroadsound;

� low water occurs 3h before mean sea-levelbut high water occurs 3.3h after mean sea-level; and

� on average, the ebb stream runs for 6.3hand the flood stream runs for 6.2h,although variations of up to 20min onthese times have been observed.

A consequence of these effects is a slightlystronger ebb stream to the north and a phaselag of the tidal stream with the times of highand low water. Peak ebb flows occur aboutone hour after high water and the peak floodstream is approximately one hour after lowwater.

The characteristics of the tide can be describedaccurately by a set of harmonic constituentsderived from a long time-series of water levelobservations. A standard harmonic analysisyields more than 100 constituents that canbe used for accurate tidal predictions. Thelongest periodicity considered in a harmonicanalysis is generally taken as 18.6 years. Thehighest predicted water level over an 18.6year ‘epoch’ is known as the HighestAstronomical Tide (HAT). Correspondingly,the lowest predicted water level is the LowestAstronomical Tide (LAT), which is commonlyused as a chart datum for reporting depthsfor navigation purposes.

Table 12 shows the tidal planes for MackayOuter Harbour, the standard port in the region,taken from the Queensland Tide Tables(Queensland Transport 1999). The BeachProtection Authority’s storm tide gauge, inoperation since 1975, is the primary tidegauge in the region (figure 17 providespercentage exceedance data for MackayOuter Harbour tides).

As part of the field data acquisition undertakenfor this study, specific measurements weremade to investigate the tidal characteristicsof the region. Simultaneous water level andcurrent recordings were obtained for anumber of locations as shown in figure 18.These were made by pressure recorders andelectromagnetic current meters deployed onthe seabed, along with vessel-mountedcurrent meters.

A series of recordings were obtained with anacoustic doppler current profiler (ADCP),deployed from a small vessel, which enableddirect measurement of the vertical structureof the flow. Data was obtained over a numberof transects in the vicinity of Mackay Harbourand the adjacent coastline.


Figure 16 Data summary, S4 current meter (Oom shoal) 19–21 July 1992Table 12 Predicted tidal planes for Mackay Outer Harbour

Relative to Relative to chart datum (m) AHD (m)

Highest Astronomical Tide (HAT) 6.41 3.47

Mean High Water Springs (MHWS) 5.28 2.34

Mean High Water Neaps (MHWN) 4.06 1.12

Mean Low Water Neaps (MLWN) 1.94 –1.00

Mean Low Water Springs (MLWS) 0.72 –2.22

Lowest Astronomical Tide (LAT) 0.00 –2.94

Numerical modellingTo assist in the quantification of tidal flowsacross the study region and to extend thevalue of the limited field measurements,numerical modelling of tides in the Mackayregion was undertaken using two modelsdeveloped in the MIKE 21 HD modellingsystem (DHI 1998). MIKE 21 HD simulatesunsteady two-dimensional flows in one-layer(vertically homogeneous) fluids by solvingthe vertically integrated form of the Navier-Stokes equations using an alternating-direction, implicit finite-difference technique.A review of the field data of vertical currentprofiles indicated that the flows are wellmixed and the depth-integrated assumptionof the two-dimensional model is justified.

A regional model (50 by 70km) with grid sizeof 500m was prepared to cover the coastbetween Cape Hillsborough and south of HayPoint (the extent of the model is shown infigure 19). The boundaries of the model werepositioned to coincide with locations of waterlevel recording stations. Nested within theregional model, a local model (16 by 36km)was constructed with grid size of 100m.

The open boundary conditions of theregional model were derived from theavailable water level measurements, whichincluded typical spring and neap tideperiods. Bed friction and eddy viscosity(turbulent mixing) parameters werecalibrated to provide the optimum matchbetween simulated and recorded waterlevels and currents at a range of locations inthe model domain.

Boundary conditions for the local model werederived from the regional model. Theoperation of the model was then verifiedagainst recorded water level and current dataat locations close to the centre of the studyarea.

A representative distribution of peak meanspring flows for ebb and flood streams(figure 20) indicates tidal currents in theorder of 0.5–0.6m/s throughout the region.

Characteristics of the tidal flows include:

� the primarily cross-shore flows at lowwater levels on the tidal flats;

� the disturbance that various featuresincluding headlands, islands and reefscause to the overall flow patterns; and

� the influence of the harbour walls.


Figure 18. Water level exceedance plot, Mackay Outer Harbour

Figure 19 Location of Mackay tide gauges and waverider buoys


Figure 20 Peak mean spring flows

An examination of the effects of the harbourwalls on the tidal flows was undertaken(figure 21 shows typical tidal velocities for apoint approximately 500m seaward of theharbour before and after construction) andindicates that velocities may have increased byup to 30 percent. A similar examination of therelative effects of the recent harbour extensionworks has shown that no detectable change intypical tidal flows in this area has occurred.

Other influencesThe dominant oceanic current along theeastern Queensland coast is the East AustralianCurrent. This is part of the general SouthPacific circulation and extends from the CoralSea along the coast to southern New SouthWales. A description of the East AustralianCurrent is given by Cresswell (1987).

At locations near Cape Moreton and CapeByron the current has been observed to flowat velocities in the order of 2m/s, but in theMackay region the effect of the East AustralianCurrent is negligible. The main component ofthe flow occurs near the edge of the continentalshelf seaward of the Great Barrier Reef. Therelatively high flow resistance of the reefmatrix reduces the component of the EastAustralian Current inside the Great BarrierReef to almost zero.

Freshwater flows can have a significantlocalised effect on coastal hydrodynamics.The Pioneer River is the region’s majorcatchment system and episodically produceshigh discharge flows that can extend largedistances into coastal waters. Discharges of4,000m3/s are known to have caused floodingin Mackay, although peak flows of up to10,000m3/s have occurred. The interaction ofhigh-discharge flood flows with nearshoretidal flows is highly dependent on the stateof the tide (figure 22 shows indicative modelresults for a medium flood event in thePioneer River interacting with the nearshoretidal currents).

Short-term variations in water levels andcurrents in the region are primarily caused bywind. The standard persistent south-easterlytrade wind flow in the region during the dryseason months leads to a weak northerlycurrent along the coast. This seasonallydependent flow results in an associatedwater level increase, which can be extractedfrom the harmonic analysis of tide data.

Of particular interest are high wind events suchas tropical cyclones, which can significantlyaffect coastal water levels and short-termcurrents. Storm surges are a major hazard inthe region.

Extreme water levelsThe understanding of the likely effects ofextreme events is important for quantifyingpotential coastal hazards of coastal erosionand storm tide inundation. A severe stormsuch as tropical cyclones can be expected toinitiate significant localised coastal changedue to the combined impact of increasedwater levels, extreme currents and high waveattack. This may result in loss of upper beach,possible dune breaching or overtopping, andreshaping of offshore banks and shoals. Thepossible coexistence of a storm tide with anexisting flood condition in the Pioneer Riverwould increase river flood levels aboveexpected values.


Figure 21 Effect on tidal velocities, pre and post Harbour construction

During the period from November through toMay, Mackay is vulnerable to the effects ofsevere tropical cyclones, which are capableof inducing storm surges of up to five metresin magnitude. While the high tidal rangeprovides some protection from inundation,numerical and statistical studies show thatMackay’s risk of exceeding normal tide levelsis amongst the highest of any section of theQueensland coast (Harper 1998).

In January 1918, Mackay was the site of oneof the most significant storm surges ever seenin Australia. The events surrounding that dayhave been summarised by Gourlay and Hacker(1986). A severe tropical cyclone with a centralpressure of approximately 935hPa crossedthe coast just north of the settlement andgenerated a storm surge of approximately3.7m. This combined with the tide at the

time to produce a storm tide level of 5.4mAHD, extensively flooding Mackay by up totwo metres above HAT. This event isestimated to have an average recurrenceinterval of approximately 500 years. Severalships moored at the wharves were sunk,disabled or washed ashore. The northern halfof the Sydney Street bridge was washedaway after a ship had been driven against itsdownstream side by the storm tide. Two daysafter the storm tide impact, the extensiverainfall generated by the cyclone hadproduced a flood in the Pioneer River, whichapparently reached levels similar to that ofthe storm tide.

In recent years the ackay region has notbeen subject to any serious storm tide threats.In 1956, tropical cyclone Agnes caused a1.4m surge, and when tropical cycloneAlthea crossed the coast near Townsville in 1971, Mackay registered a 0.9m surge. In March 1997, tropical cyclone Justin wascentred some 500km offshore and generateda storm surge of almost 0.8m. As this eventcoincided with spring tides, maximum waterlevels exceeded HAT by a small margin.

In 1985 the Beach Protection Authoritycommissioned Blain, Bremner and Williamsto complete a study of the joint probabilityaspects of surge and tide in the Mackay region(BPA 1985). This was based partly on theearlier numerical hydrodynamic modellinginvestigations by Sobey et al. (1977) andHarper et al. (1977). These early studiesprovided depth-integrated numericalhydrodynamic model results for a series ofnine design cyclones (three tracks each ofthree different intensities) located to causepeak surge conditions at or near Mackay. The model was based on a five-nautical mileresolution and included the shape of thecoast, the undersea bathymetry and theGreat Barrier Reef, but did not consider tidaleffects.


Figure 22 Model results, Pioneer River medium flood event (5000m3/s)a) ebb tide b) flood tide

Table 13 Predicted storm tide levels for the Mackay region

Site Storm tide relative to AHD Wave set-up50yr 100yr 500yr 1000yr 10,000yr (m)(m) (m) (m) (m) (m)

Hay Point 3.9 4.2 4.9 5.2 6.2 0.3

Mackay 3.8 4.1 4.9 5.2 6.2 0.5

Slade Point 3.7 4.1 4.8 5.1 6.1 0.5

Shoal Point 3.7 4.0 4.7 5.0 6.0 0.5

The BPA (1985) study extended the 1977 workby using the numerical model predictionswithin a statistical simulation model. Thisallowed the predicted surge from a cyclone ofany intensity to be combined with a randomlygenerated astronomical tide to determine thetotal storm tide level. The statistics of cyclonecharacteristics were also developed for allcyclones within a region 300 nautical milesnorth–south and 150 nautical miles offshorefor the period 1939 to 1980. An averagefrequency of occurrence of 0.76years betweencyclones entering that region was derived.

These results were then assessed in terms ofthe probability of exceedance of storm tidelevels at a number of sites (table 13) for arange of return periods. Separate values forpeak wave set-up values were also includedin the report recommendations (table 13).


IntroductionWave effects are a critical component of theregional coastal processes. Wave action andwave-induced currents in the nearshore zoneare generally the principal mechanisms ofsediment transport and coastal erosion.

The Mackay region is afforded someprotection against Coral Sea wave energyby the Great Barrier Reef. However, the outerreef formations extend more than 100km to the east at this latitude and create arelatively wide continental shelf with a south-easterly fetch in the order of 500km. Thisfeature, when considered with the dominantsouth-easterly wind direction, provides themechanism for significant localised wavegeneration (figure 23 illustrates the fetchesrelevant to the Mackay wave climate).

Locally generated wind waves, referred to assea, are the most important component ofthe wave climate in the region. The swellcomponent, waves generated from distantsources, is of less importance. The CapricornChannel is the major opening in the Reefthrough which swell propagates into the area.

A detailed assessment of the wave climate of the region has been undertaken. Studieshave included:

� an analysis of recorded wave data;

� estimation of the long-term, directionalwave climate through hindcasting; and

� numerical modelling of wavetransformation processes to determinewave climate information at inshorelocations.

Wave recordingWave recording has been undertaken for theBeach Protection Authority in the Mackayregion since 1975. A near-continuous seriesof wave data is available for the stationlocated near Bailey Islet, approximately 30kmoffshore from Mackay, from September 1975(figure 19 shows the position of waverecording sites in the region).

In the period 1988 to 1990, wave data wasrecorded for a number of inshore sites. Thesesites have different exposures to waveconditions compared to the Mackay stationdue to the sheltering effects of adjacent

headlands and the wave transformationeffects of the offshore bathymetry (table 14lists the active recording periods of thevarious stations).

The standard wave recording and analysisprocedure is described in the wave datasummary report for the Mackay region (DEH1998). Recorded data are analysed andarchived in the form of wave spectra and anumber of standard sea state parameters.Parameters include:

� significant wave height (Hsig), the averageof the highest one-third waves in a record;and

� peak spectral period (Tp), the wave period corresponding to the peak of thewave spectrum.

Where both sea and swell waves coexist, thewave spectra tend to have a distinctive multi-modal shape. Analysis of wave spectrawas undertaken to assess the relativecontribution of sea and swell components tothe total wave climate. This analysis wasbased on a procedure that examines theshape of the spectra to determine the ‘split’frequency. Typical swell wave componentsare less than 0.5m therefore it wasconcluded that swell can be excluded fromthe overall wave climate.

The Mackay wave recording station has beenoperated primarily as a non-directionalsystem. In April 1995 the equipment wasupgraded to enable directional wave recording.Data analysis is similar to analysis of thenon-directional wave data but it also providesdirectional spectra. The standard sea-stateparameter that describes wave direction isthe mean direction corresponding to thepeak of the spectrum. The directional wavedata, combined with a wave hindcastingstudy, enable a directional wave climate forthe region to be estimated.

Wave hindcastingHindcasting is the prediction of historicalwave conditions from recorded wind data.The 22 years of recorded wave data havebeen supplemented with a hindcasting studyto determine a long-term average directionalwind wave climate. This has provided:

� a more reliable long-term average byextending the data record back to 1957, a total of almost 40 years;

� wave direction information; and

� filling in of gaps in the recorded wave data.

The wave hindcasting was based on winddata recorded at three locations by the Bureauof Meteorology: Mackay (Mount Bassett),Creal Reef (150km north-east of Mackay) andGannet Cay (350km east-south-east of Mackay).The wind data input was a composite fromthe three sites, verified against a short-termrecording station established on Bailey Isletfor the Beach Protection Authority.

Wind wave predictions were computed usingSEARAY, the simplified fetch-limited spectralwave growth model developed by Walker (1989).This required the establishment of a radialgrid centred on the Mackay wave recordingsite near Bailey Islet. Measured wave datahas been used to verify the operation of themodel and other supporting assumptions, aswell as supplanting modelled data for theperiods when measurements wereunavailable (figure 24 summarises the waveclimate for the region over the period 1960to 1996 derived from recorded data and thewave hindcasting). The majority of all wavescome from the east-south-east and south-east sectors, with significant wave heightsless than 1.0m and a period of three toseven seconds.

10 Waves


Table 14 Recording periods, Mackay wave buoys

Buoy Period

Mackay 19/9/1975 – present

Harbour Beach 11/3/1986 – 7/4/1987

Blacks Beach 12/5/1987 – 6/5/1988

Bucasia Beach 19/5/1988 – 11/5/1989

Far Beach 6/2/1990 – 18/2/1991

Inshore wave conditionsWaves propagating from deeper water toinshore areas of the Mackay region undergoa transformation process influenced mainlyby the change in water depth. This is alsoaffected by the high tidal range and strongtidal currents in the region.

The MIKE 21 Nearshore Spectral Wavemodelling system was used to describe thepropagation, growth and decay of short-periodand short-crested waves from the offshorearea to the shore. By using a finite differencetechnique, the model accounts for the effectsof wave refraction, shoaling, bottom frictionand wave breaking (DHI 1998).

A wave model for the region was constructedover three grids corresponding to the majordirectional sectors of south-east, east andnorth-east. The bathymetry in each grid wasdigitised at a resolution of 500m by 125m.Data from the inshore wave recording stationswere used to verify the operation of the model.More than 1,300 model runs were undertakento construct inshore directional wave climatesfor four locations. Wave climate informationwas described with a resolution of 0.5mwave height, two seconds wave period and10° wave direction.

Additional model runs were undertaken toassess the effects of the tidal elevation andtidal currents on the propagation of wavesacross the region. The tests indicated thatthe wave-current interaction and tide rangehave little overall effect on the nearshorewave climate. The maximum observed effecton wave height was in the order of sevenpercent, but when the approximately equalprobability of ebb and flood conditions isconsidered, the overall bias is negligible(figure 25 summarises the inshore directionalwave climate data determined from themodelling).


Figure 24 Percentage occurrence of wave height and period (1975 to 1996; from DEH 1998)and wave direction from composite wave record (1960 to 1996)

Extreme eventsExtreme wave events can have a majorimpact on the Mackay coastal region. Severewave conditions are often associated withtropical cyclones, although Coral Sea lowpressure systems and, to a lesser extent, tradewind surges also cause high wave conditions.

An analysis was conducted on the Bailey Isletrecorded wave data, supplemented withhindcast information, to develop estimates ofextreme wave statistics. A set of 58 peak stormwave heights was derived from the availabledata over the period September 1975 toDecember 1997.

Synoptic records were reviewed for all theidentified storms in order to classify eventsinto common types. The dominant stormcategory is the tropical low pressure system,which includes tropical cyclones, Coral Sealows and ex-cyclones. These systems havethe potential to generate sustained periodsof onshore gale force winds and are oftenenhanced by the effects of adjacent areas ofhigh pressure lying to the south of the region.A number of lower energy storms (10 out of58) were attributed to trade wind events.

An analysis of the inter-arrival times of theset of identified storms has shown that thereis a high likelihood (almost 50 percent) thatan event will be followed by another within60 days. This clustering of events is importantin the assessment of beach erosion due tothe cumulative effects of severe storm wave conditions.

Estimates of extreme wave statistics havebeen calculated from the set of peak stormwave height data following the methodrecommended by Goda (1988). Only stormevents attributed to tropical cyclones andtropical lows were considered. Data for thetrade wind storm type were excluded fromthe analysis, primarily because of the limitedpotential of this type to generate extremewave conditions.

The calculation of extreme wave statisticshas enabled estimates to be made ofextrapolated values of storm wave heightsfor a range of return intervals (table 15). It isnoted that the highest peak wave height inthe data set for tropical cyclone Justin (March1997) corresponds to an average returninterval of approximately 32 years. This isnotable since Justin did not cross the coastnear Mackay. Peak wave conditions (threehourly average Hsig of 4.74m) occurred whenthe system was centred approximately500km offshore.

The historical record indicates a significantnatural variability in the occurrence of severestorm events. Much of this variability isassociated with the correlation of tropicalcyclone activity with the Southern Oscillation.

The negative phase of the SouthernOscillation generally coincides with coolersurface temperatures in the Coral Sea andtends to promote the persistence of westerlywinds aloft, leading to a reduced number oftropical cyclones in the region.


Figure 25 Inshore directional wave climate

Figure 26 Comparison of inshore and offshore directional wave energy

It is apparent that the period of availablewave recordings has coincided with agenerally negative trend in the SouthernOscillation Index (figure 14) and a relativelyquiet period in tropical cyclone activity alongthe east coast of Queensland. It is considered,therefore, that the calculated statisticsprobably underestimate the potentialextreme values over the longer term.

The direction of storm waves can have animportant bearing on the overall effects oncoastal processes. Estimates of wavedirection at the time of the storm peak havebeen determined from the wave hindcastingand the recorded directional wave spectra(figure 27) indicating a strong bias to the

east to south-easterly sector. This is largelydue to the restricted fetches for all otherdirectional sectors.

Joint probability of wavesand water levelsThe overall effect of high wave conditions oncoastal processes is highly dependent on thewater level. For example, a severe stormcoinciding with neap tide conditions wouldhave less impact on beaches than a moremoderate event in conjunction with a largespring tide. In the Mackay region, considerationof the large tide range is critical in evaluatingthe impacts of extreme events.

The probabilities of waves and water levelsare not independent due to the commonforcing of extreme waves and storm surgesby tropical cyclones and other severe events.Numerical simulation of the two effects inconjunction is required to correctly estimatejoint probabilities.

A storm tide risk assessment study wasundertaken at nearby Hay Point (BBW 1984)and included some limited spectral wavemodelling. The wave model results were thencombined with the storm tide results toassess the joint probability of wave heightand storm tide level. The study also includedMackay as a reference point (figure 28summarises these results in terms of thelikelihood of experiencing a given significantwave height at the same time as a givenstorm tide level. For example, there is a 45percent chance of not exceeding a five metrewave height at or above the 100-year returnperiod storm tide level and only a 30 percentchance at the 500-year return period level).

At the lower end of the range, extreme waveestimates from the BBW study correspondclosely with the values derived from therecorded data (table 15). The extreme valueassociated with the 50-year return period isestimated as a height of 5m (compared with4.9m given in table 15), the 100-year valuebeing 5.4m (compared with 5.2m in table15). The extreme wave height associatedwith a 1000-year return period is estimatedas 7m.


Table 15 Storm wave heights for selected return intervals

Average return interval (years) Hsig (m)

2 3.4

10 4.2

50 4.9

100 5.2

Figure 27 Directional distribution of extreme waves

Figure 28 Predicted return period of tropical cyclone wave heights in the Mackay region

IntroductionA large proportion of coastal sedimenttransport throughout the Mackay regionoccurs in the surf zone. In order to makereasonable estimates of sediment transportrates, it is therefore necessary to accuratelyquantify the key surf zone processes.

Waves propagating into shallow water undergoa number of transformation processescaused by the influence of the seabed. Thewave face becomes steeper and reduces inforward speed and the oscillatory motionbecomes more asymmetric. This processcontinues as the depth decreases until thewave form becomes unstable and breaks.Broken waves continue across the surf zonebefore finally dissipating in the swash zone.Important processes to consider include:

� the onshore flow, or mass transportof water;

� a corresponding return flow directedoffshore that may be in the form of arelatively weak diffuse flow and/orchannelled into rip currents;

� the generation of oscillatory currentsat the seabed;

� a local increase in water level, known aswave set-up; and

� the generation of a steady state longshorecurrent by waves approaching theshoreline at an angle.

The wave-induced longshore currents interactwith the nearshore tidal currents and areoverlain with the orbital current field of eachindividual wave. The net cross-shore currentsgenerated by the balance between onshorewave-driven flows and return flows alsointeract with tidal currents, particularly on thewide intertidal areas. The shallow water waveprocesses are complex and difficult to describecomprehensively. The large tidal range andstrong nearshore tidal currents in the Mackayregion add to the complexity.

Only limited field data of surf zonehydrodynamics in the Mackay region areavailable. These data include COPE (CoastalObservation Programme — Engineering)observations of nearshore waves andcurrents and a short-term current meteringcampaign undertaken for the BeachProtection Authority in 1992.

The data show longshore current velocities ofup to 1m/s and the strong influence ofnearshore tidal flows.

Numerical modellingQuantifying surf zone processes has beenundertaken using the Unibest CL+ (version5.01) numerical modelling system developedby Delft Hydraulics (1999). The Unibest modelcomputes the wave and current distributionacross an arbitrary beach profile, taking asinput the wave and current conditions at theseaward end of the line. Using linear wavetheory, empirical formulae and energy balanceconsiderations, the model determines:

� wave decay through the surf zone;

� wave set-up;

� wave-induced steady state longshorecurrents; and

� the near-bed orbital currents.

A number of assumptions are present in themodel formulation; these include the use oflinear wave theory in the surf zone and theassumption of straight and parallel nearshoredepth contours. Additionally, Unibest CL+does not consider cross-shore flows. Despite these limitations, this approach is

considered to be sufficiently accurate for thepresent study in estimating longshoresediment transport rates.

The model computes longshore currentsacross a profile from the balance betweenwave radiation stresses and friction. Thefriction component is dependent on oscillatoryand steady state velocities. The intensity anddistribution of the modelled wave-inducedlongshore currents is dependent on wavecharacteristics and the bottom roughness(kb). The choice of values for this parameter iscritical in the representation of longshorecurrents and, therefore, sediment transportin the model. The value adopted for theparameter kb was 0.25. This choice providedthe closest agreement between the modeland field data.

11 Surf zone processes


Blacks Beach and COPE Station in the foreground. COPE data provided valuable verification of numerical models.

Table 16 Relative probability of tidal conditions

Condition WL (m) % occurrence

slack 0.00 24

neap flood –1.00 24

spring flood –2.22 13

neap ebb 1.12 26

spring ebb 2.34 13

The strong effects of the tide in the regioninfluenced the selection of boundaryconditions for the Unibest CL+ model. Fivetidal conditions were used, corresponding toflood/ebb and neap/spring combinationsalong with a slack water case. The relativeprobability of each case was derived from thewater level probability density function andan assessment of tidal flow data (table 16).

Wave climate and tidal current data wereextracted from the numerical models (fortidal current details see table 17).

The surf zone processes at Mackay arecomplicated by topography, bathymetry andthe large tidal range. The Unibest CL+ modelis one-dimensional and does not considerthe two-dimensional effects of tidal flats andoffshore shoals. The wide tidal flats south ofthe Pioneer River mean that the surf zone canextend as far as 4km from the dunes at lowtide. The bays in the lee of headlands pose asimilar problem, to a lesser extent.

The shoals at Blacks Beach reduce the waveheight reaching the beach. The combinationof the sheltering effects of Slade Point andthe nearshore shoals leads to complex surfzone processes at Blacks Beach.


Table 17 Longshore tidal current speeds and depths used in Unibest model

Beach Spring ebb Neap ebb Neap flood Spring flood Depth(m/s) (m/s) (m/s) (m/s) (m AHD)

Far/Town –0.30 –0.13 0.13 0.18 11.2

Harbour (S) –0.47 –0.20 0.24 0.38 14.3

Harbour (N) –0.56 –0.26 0.29 0.47 14.8

Blacks –0.31 –0.18 0.16 0.22 7.5

Bucasia –0.36 –0.18 0.19 0.30 11.2

IntroductionUnderstanding of coastal sediment transportis an important component in coastal zonemanagement. Sediment flows shape thesystem of dunes, beaches and offshorebanks that are crucial for coastal protectionand beach amenity. Estimates of longshoresediment transport rates within the studyarea are required for an assessment of theoverall sedimentation regime and canprovide an insight into potential long-termchanges in the shoreline position andsediment budget.

Sediment transport in the Mackay coastalregion is driven primarily by the action of wavesand tidal flows. In general, waves from thepredominant south-easterly sector and thedominant northward-setting ebb tidal streamcombine to drive sediment in a generallynortherly direction through the study area.

The large tidal range of the region has animportant bearing on sediment transportpatterns due to the variation of water level atthe shoreline as well as the generation oftidal currents. Both steady state and oscillatoryflows play important roles in sedimentdynamics, and the two interact with eachother via the wave and current boundarylayers. It is therefore critical that the two areconsidered together, even though waves andtidal currents are generated by independentprocesses.

Longshore transportmodellingA number of empirical and semi-empiricalsediment transport formulae have beendeveloped for use in coastal applications.The commonly used formula of van Rijn (1989)is appropriate for use in the Mackay regionas it considers the processes of entrainment,transportation and deposition under theaction of waves and steady currents.

The application of this formula in this studywas primarily through the Delft Hydraulicssoftware system Unibest CL+ (version 5.01).Unibest CL+ is a one-dimensional modellingsystem only. It combines a model of nearshorehydrodynamics and the sediment transportmodel to determine longshore sedimenttransport perpendicular to a fixed profile.

A major assumption in this approach is thatthe local coastal section is treated asprismatic: that is, the local nearshore depthcontours are assumed to be straight andparallel. This assumption is acceptable overrelatively long and continuous coastal sections,but it does not allow detailed study of two-dimensional sediment transport aroundcomplex topography (as in the lee of headlands).

Estimates of net sediment flows wereaveraged over time periods considerablylonger than individual tidal cycles or stormevents. This provided estimates of long-termaverage net sediment transport rates due tothe wave climate and the tidal current climateassociated with the astronomical tide.Nearshore wave and current conditions areinput into Unibest in the form of a climate,each condition being assigned a relativeduration. The model integrates the resultsfrom each condition to determine the totalaverage sediment transport rate.

The sediment transport formula of van Rijnuses D50 and D90 parameters to representthe sediment size. The values adopted forthis study are derived from average COPEmeasurements of sediment size and areshown, along with their corresponding fallvelocities, in table 18. The density of thesediment was taken as 2650kg/m3. Jones(1987) conducted an extensive sedimentsurvey further offshore (sample locations areseen in figure 29). This study classifiedsediment units by the mean grain size andthe degree of sorting (figure 30).

The Unibest CL+ model assumes thesediment size is constant across the profile,but analyses of sediment samples showthere is some variation in sediment sizesacross most profiles.

This was taken into account in the modelcalibration process (values adopted for othersediment and wave parameters are shown intable 19).

12 Sediment transport


Figure 30 Mean grain size versus sorting forsandy sediment units (from Jones 1987)

Table 18 Sediment sizes used in longshoretransport model

Beach D50 D90 ws�m �m (m/s)

Far Beach 700 1000 0.079

Harbour Beach 500 950 0.059

Lamberts Beach 550 1000 0.065

Blacks Beach 350 750 0.040

Bucasia Beach 350 750 0.040

Table 19 Values of sediment and waveparameters used in sediment transportmodelling

Parameter Symbol Value

Wave breaking constant �c 1

Wave breaking parameter �2 0.7

Wave bed friction coefficient fw 0.01

Bottom roughness (m) kb 0.25

Current bottom roughness (m) rc 0.10

Wave bottom roughness (m) rw 0.10

Seawater viscosity (m2/s2) � 1.0 x 10–6

Porosity p 0.40

Reference height ratio a/h 0.01

Table 20 provides the summary output fromthe model for the four locations. The resultsshow a net average transport rate alongHarbour Beach south of about 36,000m3/amoving northwards. Volumetric analysis ofsurvey data at Harbour Beach, taking intoaccount the documented sand extractionrates in this area, has been used to verify themodelled transport rate. This model was thenapplied throughout the study area.

Figure 31 shows the distribution of longshoresediment transport across the profile atHarbour Beach south. The results show thatsediment transport is negligible beyond apoint approximately 500m offshore.

The longshore sediment transport rates havebeen derived from long-term average wave andtidal current conditions. Analysis of thecalculated rates at Harbour Beach shows that50 percent of the total longshore sedimenttransport occurs when the offshore waveconditions exceed a threshold in the order of 1.7m. This value represents an annualexceedance of five percent, therefore it is clearthat a large proportion of longshore sedimenttransport at Mackay occurs episodicallyduring higher wave energy events. The overallsedimentation patterns are therefore sensitiveto variations in the wave climate.

The transport rate reduces further north fromthe Pioneer River:

� on Harbour Beach north the rate is reducedslightly due to the change in the coastlineorientation compared to Harbour Beachsouth; and

� at the northern end of Blacks Beach, theestimated rate is reduced again. Thedifference is in the order of 5000m3/a andis attributed to the rate of supply to thenearshore shoals.

Cross-shore sedimenttransportThe short-term erosion of beaches in responseto storm wave conditions is well known andis an important consideration in coastalmanagement planning. An equally importantresponse is the shoreward transport ofsediment during moderate wave conditionsto rebuild the upper beach and dunes.

The prediction of sediment transport across abeach profile is relatively more complex thanthe prediction of longshore transport rates. Ingeneral, the net rate and direction of cross-shore sediment transport are the result of abalance between several mechanismsincluding:

� onshore movement driven by theasymmetry of wave orbital currents in thesurf zone;

� the offshore-directed return flow;

� the effects of bound long waves;

� currents generated by the incoming andoutgoing tides; and

� aeolian (wind-driven) transport of sanddriven onshore by the predominantlysouth-easterly winds acting over drysections of the beach.

The macrotidal environment accentuates thelatter two mechanisms, particularly over theareas of wide intertidal flats.

Numerical models of cross-shore sedimenttransport processes generally fall into twocategories, according to the characteristictime scale used to resolve sediment motion(Larson 1996). Microscale models attempt todescribe the processes under individual wavesand overall results are gained by integratingover time. Mesoscale models simulate thetime-averaged processes, which are the resultof many waves. Typically, mesoscale modelsare more reliable in describing broadscalebeach profile changes, such as short-termerosion in response to storm events. Thesemodels are less successful in simulatingonshore sediment transport and details suchas the formation of nearshore bars.

No attempt has been made to undertakegeneralised numerical simulation of cross-shore transport rates as part of this study.Modelling of short-term storm erosion usingthe SBEACH model has been used as part ofthe review of erosion prone areas. This isdescribed in the discussion of short-termerosion. Some information on cross-shoresediment transport has been inferred fromsurvey data and analysis of aerial photography.This was primarily used for the assessmentof movement of shoals in Slade Bay.


Figure 31 Cross–shore distribution of longshore sediment transport at Harbour Beach

Table 20 Predicted longshore transport rates

Beach Survey profile Longshore transportrate (m3/a1)

Town/Far MAC108 –

Harbour (S) MAC124 35 900

Harbour (N) MAC134 32 900

Blacks MAC159 28 000

Bucasia MAC179 20 200

IntroductionThe coastal topography in the study areacomprises a number of complex features thatreflect the interaction of the underlyinggeological formations with the continuingfluvial and coastal processes.

Topographic information has been compiledfrom a number of sources including:

� existing navigation charts and topographicmaps;

� beach profile survey data; and

� aerial photography.

Beach profiles were surveyed over 60 BeachProtection Authority standard lines by theDepartment of Transport (previously Departmentof Harbours and Marine) through the regionin 1971, 1977, 1978, 1979, 1981, 1986,1992 and 1997 (figure 32 shows the locationof all survey lines in the study region).

Low-level aerial photography (at scale1:12,000) was captured for the BeachProtection Authority in the Mackay region inMay to June 1974, August 1977, November1978, July 1981, June 1985, June 1991, June1993 and October to November 1997. Aerialphotography before 1974 was undertaken atvarious scales and coverages; most notableare the 1947 to 1948 data, captured atscales of 1:30,000 and 1:32,000.

QASCO Surveys Pty Ltd was commissioned to undertake a photogrammetric study of theregion to provide topographic information onthe nearshore and shoreline areas based onthe June 1993 photography. Additionally, a comparison of historical shorelines(represented by the Highest AstronomicalTide contour) was made for the 1947 to 1948and May to June 1974 photography. A pre-1900shoreline was also constructed from historicalfield surveys to provide a qualitative view ofcoastline changes.

Offshore bathymetryThe continental shelf in the region is relativelywide and slopes gently to the 100m isobath,located approximately 200km offshore.Depths are less than 30m in most parts. The bathymetry is relatively complex, withnumerous islands and shoal patches,notably Blackwood Shoals to the north-eastand Viscount Shoals to the south-east.

The Great Barrier Reef is located 100 to 120kmoffshore of Mackay. A significant opening(the Capricorn Channel) lies to the south-eastof the region. The configuration of the reefand the continental shelf offshore fromMackay have a significant influence on thehydrodynamics of the region.

Dudgeon Point and Hay Point lie to the southof the study area. These headlands, formingthe lower section of Sandringham Bay, havea significant coastal control over thesouthern section of the Mackay region.

Topographic featuresThe main topographic features of the region,along with representative beach profiles, issummarised in figure 33. The profile acrossFar Beach (MAC108) is typical of the coastalsection south of the Pioneer River entrance.The beach is characterised by wide tidal flatsbacked by a low frontal dune system. The tidalflats are significant, with a very flat gradientextending out to more than 2.5km offshore.The elevation of the tidal flats typicallyslopes from approximately mean sea-level tomean low water level at the seaward edge.

The dunes in this section are often quite low,having a typical height of 5 to 7m AHD.Behind the dunes are a number of small,back-barrier creek systems that drain acrossthe tidal flats. From behind the dunes, thetopography slopes gently landward throughSouth Mackay and East Mackay. These areasare relatively low-lying, with typicalelevations of 4.5 to 5m AHD.

The topography around the Pioneer Riverentrance shows a distinct delta formationwith significant subtidal features extendingout towards Flat Top Island. The coastalalignment is offset by approximately 800meither side of the river (figure 34). This sectionof coastline has shown the most change overrecent history, reflecting the high fluvial inputof sediments from the Pioneer River to thecoastal system.

The Harbour Beach profile (MAC122; figure 33)shows a distinct difference from the Far Beachprofile, having a much narrower intertidal areaand a higher dune system. The dunesincrease in height from south to north alongthis section, rising to more than 20m AHDnear Slade Point. Some dune areas have beenlevelled for residential and port purposes,mainly around the central section of the beach.

Behind the dunes are areas of low-lyingfreshwater and tidal wetlands, most notablyBassett Basin. The coastal alignment iscontrolled by the significant rock outcrop ofSlade Point and, to a lesser extent, theMackay Harbour walls. Other rock outcropsare evident including Slade Islet, DangerousReef and the small rock outcrop that separatesHarbour Beach from Lamberts Beach.

The beach profiles in this section generallyshow a monotonically-increasing, concave-upward slope and comprise two distinct parts:a relatively flat intertidal zone extending frombelow the mean water level and a steep,reflective upper beach.

13 Coastal topography


North of Slade Point, the embayments ofSlade Bay and Sunset Bay have formedbetween rocky headlands. These twosections are topographically quite similar.Common features include:

� wide intertidal areas formed from thedeposition of sediments in the lee ofheadlands (figure 35);

� beach barrier systems backed by lowdunes and tidal wetlands;

� shallow estuaries of McCreadys Creek andEimeo Creek draining into the southerncorner of the embayments; and

� narrowing beaches at the northern end ofthe embayments backed by rocky cliffs.

The Blacks Beach profile (MAC159; figure 33)is typical of the northern end of Blacks Beachand shows a significant sandy shoalapproximately 200m offshore. The beachshows a concave-upward morphology similarto that of Harbour Beach, although theinshore gradient is steeper and the dunes aremarkedly lower.

Bucasia Beach (MAC179; figure 33) isbacked by high dunes in the order of 10 to15m AHD. Rock outcrops are presentapproximately 2.5km offshore. All othertopographic aspects of the beach areotherwise very similar to Blacks Beach.


Figure 34 Pioneer River entrance (17/8/93)

Figure 35 Slade Bay (14/8/93)

IntroductionA study of the geological evolution of theregion provides an understanding of thepresent-day configuration of the Mackaycoast and an insight into the continuingcoastal processes.

The period of geological history of mostrelevance is the Quaternary period, whichextends from about 1.8 million years BP andcomprises the Pleistocene epoch (1.8 millionto 10,000 years BP) and the Holocene epoch(from 10,000 years BP to present).

A number of background studies of thegeological history of the region are available,including studies commissioned by the BeachProtection Authority. In addition, Gourlay andHacker (1986) provide a detailed descriptionof the sedimentation processes in thePioneer River and include a discussion of thegeomorphology of the river and the adjacentcoastal areas. More recently, Masselink andLessa (1995) provided a discussion of thegeomorphology of the Bucasia area.

Mean sea-levelOver geological timescales, shoreline erosionand deposition processes are closely linkedto variations in mean sea-level. During theQuaternary period, global sea-levels havevaried considerably in response to variationsin the extent of the polar ice fields. Duringthe last glaciation, about 18,000 years BP,water levels were approximately 120m belowpresent levels and the shoreline was beyondthe present location of the Great Barrier Reef.Post-glacial sea-level rise, known as themarine transgression, began about 15,000 to12,000 years BP and reached present levelsabout 6500 years BP (mean sea-levels overthe past 20,000 years are schematicallyshown in figure 36).

Sea-level changes over the later Holocenetended to vary across the region due to localisostatic movements in response to the waterload on the continental shelf. Stephens (1993)concludes that the peak of the transgression(approximately 1m above the present meansea-level) occurred about 5000 to 4000 yearsBP in the Proserpine region, then graduallyfell to reach the relatively constant modernlevel about 3000 to 1000 years ago. Gourlayand Hacker (1986) reported no evidence ofhigher sea-levels around Mackay.

Masselink and Lessa (1995) discuss thepossibility that a wave climate and tidalrange different from those of the present mayhave existed in the region during the periodof sea-level rise leading up to the peak of themarine transgression. Due to the rapidaverage sea-level rise of 13mm/a, the growthof the Great Barrier Reef may have significantlylagged behind the water level. The effects ofthe reef in providing shelter from Pacific Oceanwave energy and amplification of the tidewould also have lagged, therefore creating atide and wave window. Masselink and Lessacontend that wave energy reaching theshoreline during this period may have beenhigher than present day conditions.

Pre-Holocene geologyExtensive outcrops of bedrock are seen alongthe coast and the offshore islands. This rockis part of the Palaeozoic Campwyn Beds inthe south and the Tertiary Cape HillsboroughBeds in the north. Notable bedrock featuresalong the coast include Dudgeon Point,Slade Point, Dolphin Heads and Shoal Point.These features have had a strong influenceon the formation of the modern-dayshoreline. Other prominent features includeMount Bassett, Flat Top Island, Round TopIsland and Slade Islet. Mount Bassett is anintrusion of a more recent Cretaceousmicrodiorite formation.

The upper parts of the Pioneer River catchmentare dominated by the mountainous terrain ofConnor Range. This range is composed ofigneous granitic formations known as theUrannah Complex, which are more recentthan the Campwyn Beds. These rocks areimportant in that they are relatively prone toerosion and they decompose to sand ratherthan silts. It is likely that an extensive erodedsurface underlies the alluvium in the vicinityof the present coastline. The present-daycoastal sediments are derived predominantlyfrom material eroded from the Pioneer Rivercatchment.

14 Geological history


Figure 36 Sea-level rise over the last 20 000years (Gourlay and Hacker 1986)

The late Pleistocene land surface consolidatedduring the last glacial sea-level low. Throughoutthe region, sequences of Pleistocene agealluvial sands and clays overlie the bedrock,and near the coast they are mostly coveredby the more recent Holocene deposition. ThePleistocene sequences can be seen behindthe back barrier wetlands (figure 37).

North of the Pioneer River a number of relictbeach ridge formations of Pleistocene agehave been identified, notably in the Andergrovearea. South of the Pioneer River, thePleistocene clay surface is seen approximately300m behind the shoreline, rising graduallylandward. A relict Pleistocene depositintersecting the coastline has been identifiedin the vicinity of Dolphin Heads (figure 37).

Holocene depositionThe deposition of sediments during theHolocene has resulted in the formation of thepresent coastline. Once sea-level rise slowedto the present trend approximately 6500years BP, the coastline began to developtowards equilibrium with the new continentalshelf and wave climate. Onshore transport ofsand and other sediments from the offshorecontinental slope, which included submergedriver flood plains and deltas, contributed tothe progradation of beaches during the earlyHolocene.

Sediments are derived from two main sources:the pre-existing sand deposits drivenlandward during the marine transgressionand the more recent fluvial deposits from thePioneer River. Analysis of the surficialsediments (Jones 1987) indicates that thePioneer River is the most significant modern-day supplier of sediments to the Mackay coast.

South of the Pioneer River the median grainsize of sediments in the nearshore zone is inthe order of 0.7mm. The grain size variesmoving north from the Pioneer River. At HarbourBeach the median grain size is typically 0.55mm,while at Blacks Beach and Bucasia thevalues reduce to 0.35mm.

A delineation of two major marine sedimenttypes can be made using grain size analysis.The finer-grained sediments with relatively lowcarbonate content (primarily shell fragments)are found on the beaches and in the nearshorezone to a depth of approximately –10m AHD.These deposits are attributed to the recentsupply from the Pioneer River. The relict sanddeposits transported shoreward during themarine transgression are identified as coarser-grained sediments with higher carbonatecontent; these are found further offshore (thezone of delineation between the two majormarine sediment types is seen in figure 37).

The present-day shoreline configuration islargely controlled by the major bedrock outcropfeatures of Dudgeon Point, Slade Point, DolphinHeads and Shoal Point. These structures arerelatively erosion-resistant and have formedcontrol points for the adjacent beach systems(a schematic distribution of the historicalgeology in the region is seen in figure 37).

Gourlay and Hacker (1986) describe therelatively recent changes to the course andcatchment of the Pioneer River. Untilcomparatively recent times the course of thelower Pioneer River followed the presentpaths of Sandy Creek and then Bakers Creek,cutting through the Pleistocene coastal plain.

The evidence suggests that the uppercatchment was not as large as its presentconfiguration, resulting in lower rates offluvial supply of sediments to the coast atthat time.

At an estimated 3500 years BP, the PioneerRiver was redirected to its present locationand, due to changes in the upper catchment,now carries a significantly higher sedimentload. The development of the Pioneer Riverestuary and the adjacent coast into theirpresent-day forms began at this time.


Far Beach and Town Beach showing the complex coastal features of the Pioneer River entrance.

The mechanism of sandy barrier morphologyis described by Masselink and Lessa (1995).As the outer ridges developed in response torising sea-levels, the areas behind thembecame sheltered, allowing fine sedimentsto accumulate to form the extensive tidal andfreshwater wetland areas north of the PioneerRiver. The height and extent of the barrierformation is strongly related to sediment supply.The extensive deposits of the dune fieldsimmediately north of the river entrance canbe attributed to the large rate of sedimentsupply to the coast from the Pioneer River.

Jones (1987) theorised that during theinterval between 6500 and 3500 years BP alarge delta formed in Sandringham Bay to thesouth of Mackay. This delta has since erodedand been reworked to its present configuration,and has supplied significant volumes of sandto the tidal flats and the beaches to the north.Due to the comparatively lower rate of fluvialsupply from the previous courses of thePioneer River, the dune systems of Far Beachand Town Beach are lower in height andwidth than those of Harbour Beach. Themechanism of barrier formation was similarto that of the beaches north of the river,resulting in low-lying areas behind the beachridge of similar, but less developedmorphology.

Calculation of the average annual supplyof sand to the northern beaches has beenattempted, using radiocarbon datingfrom borehole samples. A total sand supplyto the beaches in the order of 25 000m3/aover the past few thousand years has beenestimated. It is also likely that a considerablevolume of sand has bypassed the delta andbeaches to be deposited further along thecoast or offshore. The offshore seismicsurvey reported by Hegarty (1983) indicateda sedimentary lens of considerable thicknessnorth-east of Green Island overlying thePleistocene (clay) seismic basement. Thestrong tidal flows north of Slade Point andShoal Point have acted to direct sedimentsto nearshore sandy shoal deposits.

Features identified in the offshore seismicprofiling investigation reported by Hegarty(1983) included a series of inner continental-shelf shoal systems, including the BlackwoodShoals north-east of Shoal Point. The systemshad varying morphology and seismiccharacteristics, and were interpreted by Jones(1987) as relict sand wave deposits developedduring the marine transgression. Althoughthey have a strong fluvial character, thesesediments also contain indicators of themarine environment in which they now occur.

Such indicators include a relatively highbiogenic calcium carbonate content and theshaping of the deposits by tidal currents intosandbanks and sand waves.

The estimated sedimentary supply to thebeaches and to deposits offshore from thestudy area during the Holocene totals250million m3, an annual volume of40,000m3. In addition, a considerablevolume of sediment has been deposited inSand Bay, north-west of Shoal Point. Jones(1987) concluded that the Pioneer Rivercould not have provided all the sediment forthe delta, beaches and these additionaldeposits. Some of the sediments in theoffshore shoals may have been eroded fromthe Pleistocene surface or the abandoneddelta during the marine transgression. It istherefore not possible to derive sedimenttransport rates from the geological evidence.


Shoal Point and Sand Bay.

IntroductionAn outline of the present-day sediment supplyand distribution patterns of the Mackay coastcan be inferred from the geological history ofthe region along with the analysis of recent data.

Data analysis undertaken for this studyconsists of:

� volumetric analysis of beach survey dataincluding hydrographic surveys andprofiles recorded for the Beach ProtectionAuthority’s COPE program spanning theperiod from 1971 to 1997;

� the comparison of historical shorelines byQASCO Surveys Pty Ltd using the 1947 to1948, May to June 1974 and June 1993photography and a pre-1900 shorelineconstructed from historical field surveys;

� a photogrammetric study of the PioneerRiver entrance using the available BeachProtection Authority aerial photography;and

� estimates of coastal longshore sedimenttransport fluxes based on analysis of waveconditions and tidal flows.

The work by Gourlay and Hacker (1986) onthe Pioneer River estuary and the study ofthe impacts of sand and gravel extraction onthe Pioneer River tidal reaches by GutteridgeHaskins and Davey Pty Ltd (GHD 1998) alsoprovide further information on the localprocesses (a representation, not to scale, of the sediment supply and distributionthroughout the study area is given in figure 38).

Pioneer River tidal reachesGourlay and Hacker (1986) conducted anextensive investigation of the Pioneer River,using the results from several physical modelstudies to determine the overall dynamics ofthe river and catchment system. One of thekey findings of this study was that the PioneerRiver is the major source of sedimentsforming the tidal flats and sandy beaches ofthe coast adjacent to the entrance.

Gourlay and Hacker describe how the hydrologyof the region, along with the nature of thePioneer River catchment and its geology, leadsto a comparatively high fluvial sedimentsupply rate. Prior to the construction of theweirs, an average rate of sediment supply in

the order of 200,000m3/a was estimated; thisincludes both bed load and suspended load.More recent estimates of the average sedimentyield from the Pioneer River catchment to theestuary have been made by GHD. Taking intoaccount a range of factors including thetrapping of sediments by upstream flow-control structures, estimates of the rate ofsupply of sand and gravel material to thePioneer River estuary vary between12,000m3/a and 55,000m3/a (GHD 1998).

An additional consideration is the effect ofthe weirs in reducing the maximum value ofmajor flood discharges. For a given extremerainfall event in the Pioneer River catchment,the magnitude of the peak discharge will beinfluenced by the storage effects of the weirs.Since the rate of sediment transport isproportional to the flow velocity raised to thepower of approximately three, this has apotentially significant effect on the net fluvialsupply rate to the coast.

The sedimentation patterns in the tidal reachesof the Pioneer River are complex and arecomplicated by anthropogenic effects suchas flow-control structures and commercialsand and gravel extraction operations. Theconstruction of weirs at Mirani, Marian andDumbleton has led to impoundment of largevolumes of the coarser bed material sediments,thus reducing the supply to the lower reaches.

Significant volumes of material have beenextracted from within the tidal reaches of thePioneer River and the adjacent coastal areas

since settlement began. Much of this extractionis undocumented. GHD (1998) outline therates of extraction from the various licensedsites from available records (figure 39 detailsthe various extraction sites). Over the period1976 to 1997, the average annual extractionrate under permits from the Mackay PortAuthority and the Queensland Departmentof Environment and Heritage (nowEnvironmental Protection Agency wasapproximately 88,000m3/a. This does notinclude extraction operations on the coast.

Some sections of the tidal reaches showevidence of bank erosion due to continuingnatural processes and/or associated withstructures such as training works and bridges.There is also recent evidence of accretion insome sections, including an area in thevicinity of Cullen Island and in Bassett Basin.The gradual infill of Bassett Basin is a resultof the reworking of lower estuary sedimentsby tidal flows and aeolian transport fromHarbour Beach. This infill is partially artificialbecause the construction of the training wallon the northern bank of the river has limitedthe flushing of Bassett Basin by flooding.

Overall, it is highly probable that the tidalreaches of the Pioneer River are nowexperiencing a net loss of sediments due to thecombined actions of flow-control structures,commercial extraction activities and naturalprocesses. GHD (1998) recommended thatthe permitted rate of extraction within thetidal reaches of the river be reduced from100,000m3/a to a more sustainable rate of 22,000m3/a.

and distribution15 Sediment supply


Sand extraction operations in the Pioneer River.

Pioneer River entranceThe behaviour of the Pioneer River entrance haschanged significantly since the constructionof the training walls at the river mouth (figure40). These works were originally constructedbetween 1887 and 1892, followingrecommendations of the eminent Englishharbour engineer Sir John Coode. The northernwall was modified to its present alignmentshortly after the breakthrough of the northernspit in 1898.

Gourlay and Hacker (1986, p114) summarisedthe changes to the Pioneer River bar thatoccurred more than 100 years ago:

‘In 1898, during cyclone Eline, the positionof the mouth of the Pioneer River wasaltered dramatically when the river brokethrough the original elongated East Point.Before the cyclone occurred, the riverflowed out to sea in a south-south-westerly direction parallel to the existingEast Mackay foreshore. The original EastPoint was the southernmost tip of a longthin low spit extending two km southfrom the present East Point. It was abouttwo m above high water level at itsnorthern end and less than 0.5m abovehigh water level further south.

It would appear to have been formedfrom sand brought down by the river intimes of flood and deposited on the barseaward of the river mouth. This sandwould then have subsequently moved bywave and wind action, both onshore andalongshore in a southerly direction, to form the spit.’

The mechanism for growth of the spit involvedthe transport of sediments to the bar by out-flowing currents associated with ebb tides andfloods. The sediments were then reworkedlandward and into a bank structure by waveaction. This resulted in an elongated spit thatextended southward with a slight westwardcurve at its seaward end. Gourlay and Hackerreported that the river had broken throughthe spit several times before the 1898 eventbut had always reformed to approximatelythe same general configuration.

The preferred alignment for the main riverentrance channel is presently towards thesouth-south-east. The extensive sand depositsno longer form a continuous spit structureand have the appearance of a subtidal delta.Only small sections are above the 0m AHDlevel, and one or more minor secondarychannels periodically form close to East Point

on generally east to north-easterly alignments.These secondary channels are associatedwith ebb tidal flows. The peak ebb tidal flowoccurs close to high water and the near-fieldflow is directed generally northward. Thepreferred ebb tide discharge from the estuaryis therefore across the delta towards thenorth-east.

The changes to the overall sedimentationpattern of the entrance area can be attributedto the effects of the training walls. The northerntraining wall armours the inside of the riverbank and limits the supply of sediment to thearea immediately downstream of the wall’send. This results in a terminal effect – thecharacteristic erosion of an unprotectedcoastline adjacent to a hard structure whichtends to promote the formation of thesecondary channel running eastward fromEast Point and limits the vertical growth ofthe spit. The southern training wall acts todeflect the outgoing flow eastward andreinforces the general tendency to depositsediments in the area south-east from theriver mouth. The sedimentation patternsare also influenced by the frequency andintensity of flood and storm events, and the impacts of sand extraction.


SOUTH

PACIFIC

OCEAN

Figure 39 Location of sand and gravel extraction sites


Figure 40 Aerial photograph, Town Beach to Harbour Beach south

Before the changes in 1898, the primarysediment deposition zone was further southand inshore of the present location. Over thepast 100 years the main deposition zone hasbeen in a delta pattern in the area betweenthe trained river entrance and Flat Top Island.The seaward limit of the delta is graduallyextending into the lee of Flat Top Island andis increasing in volume.

Gourlay and Hacker (1986) noted this trend ofaccretion and predicted that the coastline wouldeventually form a tombolo in the lee of FlatTop Island. The average annual accumulationof sediments on the entrance bar wasdetermined to be in the order of 40,000m3,although this was thought to fluctuate inaccordance with the episodic nature of floodflows in the Pioneer River.

A sequence of aerial photographs captured in 1962, 1974 and 1993 is seen in figure 41.The 1962 and 1993 photographs show theprimary channel with approximately thesame length. The 1974 photograph shows amuch shorter channel. This can be attributedto the effects of the flood events of 1968 and1970. The length of the channel is thereforeperiodically reduced by major flood events,which also have the effect of pushing sedimentseaward and extending the width of the delta.The photographs show the main ebb tidalchannel extending southward between 1974and 1993 in response to the growth of thesubtidal spit at East Point. The period since1974 has been characterised by a lack of amajor flood in the Pioneer River. Gourlay andHacker’s figures 6.14 and 6.16 show thesechanges for the period from 1887 to 1979.

The primary mechanism ofcontinuing deposition at thePioneer River entrance appears to be a widening of the delta in a generallysouth-easterly direction. Resultsof a photogrammetric analysis were used, inconjunction with an analysis of hydrographicsurvey data, to update the earlier estimatesof accretion rates (figure 42 summarises theanalysis of aerial photography in the vicinityof the river entrance from 1974 to 1997). An average accretion of 55m3/m/a has beenevaluated from survey data, in conjunctionwith aerial photography and can be assumedto be representative across the river entranceover a distance of 800m. The net rate of accretion is thereforeestimated to be 44,000m3/a, which


Figure 42 Bar topography, Pioneer River entrance, 1974–97

Figure 41 Growth of Pioneer River tidal delta, 1962–97

(a) 1962 (c) 1993(b) 1974 (d) 1997

compares closely with Gourlay and Hacker’sestimates. It is noted that this estimate islimited by the available data. To improve theaccuracy of future estimates, more detailedhydrographic surveys of the entrance areaare required.

Gourlay and Hacker (1986) predicted that thelow water mark (represented by the –3m AHDcontour) at the outer edge of the deltaformation would continue to progradeseaward to meet the -3m AHD contour of FlatTop Island by approximately 2042. Based onfour surveys of beach profile MAC114 between1977 and 1992, the average rate of advancehas been evaluated as 6.8m/a, supportingthe 1986 prediction.

Town BeachThe section of coast immediately to the southof the Pioneer River entrance (figure 40) hasshown a trend of accretion over recent history.Following the major flood event of 1898, theremnants of the spit that previously formedthe northern bank of the river broke away fromthe entrance system and migrated onshore tothe northern section of Town Beach. Thispattern of onshore migration of sand shoalsat the northern end of Town Beach is clearlyevident from the photogrammetric analysis ofthe aerial photography data (figure 43).

South of the Pioneer River, sedimenttransport processes are characterised by theonshore movement of sand across the tidalflats. The major supply of sediments to TownBeach is from the river entrance bar on thesouthern side of the main ebb tide channel.Sediments are deposited here by the outgoingtidal and/or freshwater flood flows anddriven onshore, primarily by the action of thepredominantly south-easterly waves.

The present-day accretion of the northern endof Town Beach is also strongly influenced bythe southern training wall structure in theriver entrance, which has anchored the beachand isolated it from the river flows. Beforethe wall was constructed, this section waseffectively part of the lower estuary.Sediments were transported into the rivermouth by wave action, entrained by the flowsin the lower estuary and recycled back out onto the entrance bar. The wall now interruptsthis process, resulting in a greater rate ofaccretion.

In general, the morphology of the TownBeach shoreline changes relatively slowly.The large tide range has a significant controlover the inshore sediment transportprocesses, due to the following phenomena:

� wave energy reaches the upper beach foronly a limited amount of time around highwater;

� waves are strongly affected by refractionand friction losses over the tidal flats andtypically generate only weak longshorecurrents at the shoreline; and

� inshore tidal flows tend to be cross-shoreand are strongly affected by friction losses.

The net rate of longshore sediment transportis difficult to assess as the processes aredominated by cross-shore wave effects and,to a lesser extent, tidal currents. The UnibestCL+ analysis indicates that the longshoretransport rate is relatively low and directednorthward. At a location near the southernend of Town Beach, a net rate of less than1000m3/a to the north has been estimated.

For the Town Beach section, data areavailable for only two survey lines, MAC114and MAC116. Analysis of beach profilesurvey data during 1977 to 1997 indicates agradual accretionary trend (table 21). This isdemonstrated by the advance of the MHWScontour (2.3m AHD) at MAC116 by anaverage of 1.85m/a.

Table 21 also shows the volume change ofthe upper beach between the 0m and 500mchainages. The apparent erosion of MAC114is a result of changes of the relict tidal delta ofa small creek that has been moving onshoreand alongshore since drainage works in EastMackay diverted the flows during the 1960sand is not indicative of the general trend.

The slow accretion observed on the MAC116upper beach profile (approximately 1m3/m/a)is supported by the photogrammetric data(figure 43). At the northern end of TownBeach, the area adjacent to the high watermark has slowly consolidated. There is alsoevidence of accretion adjacent to thesouthern training wall.

Analysis of the photogrammetric data hasalso provided an estimate of accretion rates,although it is not conclusive. The total areacovered by the 0m AHD contour on the tidalflats immediately south of the river entranceshows a weak trend of accretion although islimited by the spatial extent of the data. Thedata show large fluctuations over time, whichis probably indicative of the accuracy of theanalysis. The size of the 0m AHD contourarea is increasing at about 2,500m2/a,corresponding to a seaward advance of the0m AHD contour in the order of 2m/a.Assuming a slope of 1:250, this translatesinto a uniform increase in the bed level of8mm/a and corresponds to a rate ofaccumulation in the order of 4000m3/a.

Over recent history, the Town Beach coastlinehas changed considerably as a result ofengineering works and natural processes. Atthe beginning of the 20th century, the EastMackay area was a low-lying wetland areapartially inundated by tides and prone toflooding, like the present area adjacent toEast Gordon Street. Several major sandextraction campaigns for reclamation workshave been undertaken to establish thepresent-day residential lands.

An unknown volume of material was used inthe original East Mackay reclamation works,bounded approximately by Goldsmith, EastGordon, Hoey and Evan Streets. The detailsof quantities, timing and the location ofborrow areas are not available, but it is likelythat the majority of the material was sourcedfrom the remnants of the pre-1898 East Pointspit, just offshore from the reclamation area.

Binnington Esplanade and the subdivisionbehind it were reclaimed in 1964, mainlyusing sand dredged from the tidal flatsimmediately seaward. Erosion problemssoon occurred and a rock wall wassubsequently constructed to protect theroad.


Flat Top Island showing accretion of river sediments.

The dredged area has gradually infilledthrough onshore and longshore sedimenttransport, although it can still be seen inrecent aerial photographs.

In 1985, the Land Administration Commission(LAC) commissioned the dredging of280,400m3 of sand for further reclamation ofresidential lands. The reclamation was locatedon the southern side of the small creek at thesouthern end of Town Beach, locally knownas Pothole Creek, effectively extending theoriginal reclamation area. The borrow area,located approximately 500m offshore, haspartially infilled although it is still clearlyvisible in 1997 aerial photography.

As part of the East Mackay reclamation works,the drainage for the area was diverted southinto Shellgrit Creek. The small creek at thesouthern end of Town Beach, locally known asPothole Creek, subsequently closed, resultingin changes to the inshore sand deposits. Thedeposits, which were the tidal delta of thecreek, have since migrated onshore andalongshore.

Longshore transport has resulted indeposition of the sand on either side of thecreek entrance, and towards the aforementionedborrow area near Town Beach.

It is likely that this process will continue,resulting in accretion seaward of theBinnington Esplanade rock wall.


Figure 43 Town Beach sand shoals (photography captured 17/8/1993)

Table 21 Survey data analysis for Town Beach (refer figure 32 for location of profiles)

Survey profile Volume to 0m contour MHWS (+2.3m) contour Shoreline (4.6m AHD contour)(m3/m/a) (m/a) (m/a)

MAC116 1.12 1.85 2.01 (4m contour)

MAC114 –9.45 – –0.25

Table 22 Survey data analysis for Far Beach (refer figure 32 for location of profiles)


MAC112 –1.56 –0.02 –0.29

MAC111 –3.40 –0.88 –0.08

MAC110 –3.28 –0.42 –0.66

MAC109 –2.87 –1.24 –1.29

MAC108 1.29 –1.91 –1.85

Far BeachAs at Town Beach, sediment transport in thevicinity of Far Beach is mostly cross-shorewith a weak northerly component. At thesouthern end of Far Beach, the net longshoresediment transport close to the shoreline isapproximately zero, although the grosslongshore rate is significant. At the northernend of Far Beach, the net longshore sedimenttransport at the shoreline is directed northwardat an estimated rate of less than 1,000m3/a(an image of Far Beach is given in figure 44).

Before the late 19th century changes to thePioneer River entrance, this longshoretransport rate was approximately balancedby an onshore supply of sediments from theestuary. The historical entrance of the PioneerRiver was located just offshore from thecentre of Far Beach and provided a continuingsource of natural beach replenishment.Therefore over the past 100 years, theonshore supply of sediments to Far Beachhas been reduced, resulting in constantshoreline realignment.

Numerical modelling illustrates the indicativeflows associated with a medium flood eventin the Pioneer River interacting with thenearshore tidal currents and shows themechanism for deposition of sedimentssouth of the river entrance during floodevents. The actual sedimentation patternsduring a flood event are influenced by the

tidal conditions during the period of peakdischarge. Ebb tidal flows tend to turn theriver discharge towards the east away fromthe coast. The input of fluvial sediments tothe intertidal area offshore from Far Beach istherefore highly episodic as it depends on theoccurrence of a flood event in conjunctionwith favourable tidal conditions.

Analysis of the beach profile survey data iscomplicated by the characteristics of thearea. The very flat profiles and the slowlychanging nature of sand shoals on the tidalflats make it difficult to evaluate trends. Inparticular, volume calculations are highlysensitive to small survey datum errors overthe tidal flats that extend for more than 3km.

Analysis of the available survey data for FarBeach during 1971 to 1997 indicates a trendof erosion (table 22). Southward fromIllawong Park, there has been an overallaverage loss of volume above the 0m AHDcontour in the order of 3m3/m/a and anaverage recession of the MHWS contour ofalmost 0.9m/a. The rate of erosion ismarkedly lower between Illawong Park andTown Beach.

The Far Beach coast has been considerablyaffected by human activities. There has beena history of sand extraction activities aroundFar Beach, mostly undocumented, both in thedune areas and on the nearshore tidal flats.Until recently, many areas of dune vegetation

were heavily disturbed by pedestrian andvehicle use, resulting in lowered dune levels.

The highest rate of recession of the upperbeach has been observed at the southernend of Far Beach near the entrance ofShellgrit Creek. This is partially related to thefluctuations of the primary ebb tide channelof the creek. Modifications to the EastMackay stormwater drainage system over thepast 20 years have probably resulted ingenerally higher flows through the creekentrance and subsequent changes to thelocal coastal alignment.

Illawong Beach Resort, previously MuddiesCrab Farm, has been established near thebeach adjacent to the entrance of ShellgritCreek. The design of the recent upgrade ofthe resort complex recognised the potentialfor a serious storm erosion event and aprotective rock wall was included as part ofthe works to provide a line of defence. Thiswall forms part of the lagoon in front of theresort and to date has not been exposed tostorm conditions.

A rock wall has also been constructedseaward of Illawong Park recreation reserveto halt the rate of coastal recession. This hasresulted in a localised drop in beach levelsand a noticeable recession of the adjacentcoastline. These effects are partially relatedto the effects of the rock wall itself, but areindicative of the continuing erosion trend.


Rock wall constructed seaward of Illawong Park

Table 23 Survey data analysis for Shellgrit Creek to Bakers Creek (refer figure 32 for profile locations)


MAC106 insufficient data

MAC104 –5.03 –0.73 –0.61


MAC100 2.40 2.08 2.02

Shellgrit Creek to Bakers CreekAs at Far Beach and Town Beach, the coastalsection south of Shellgrit Creek is stronglyinfluenced by the nearshore tidal flats (figure44). Sediment transport is dominated bywave-driven cross-shore processes across thetidal flats, with a weak southward longshorecomponent at the shoreline. It can be inferredthat the null point of net longshore transportis in the vicinity of Shellgrit Creek.

Due to the sheltering effect of Dudgeon Point,the net longshore transport is southwardalong the inshore zone. The southwardsediment transport towards Bakers Creekleads to a general trend of accretion aroundthe creek entrance and a gradual growth ofthe spit. The zone adjacent to the tidalchannel is influenced by wave–currentinteractions and tends to form a low bank.

Geological evidence indicates that the spitforming across the creek entrance has grownsouthward relatively slowly since the PioneerRiver established its present course morethan 3500 years ago (DPI 1995).


Figure 44 Aerial photograph, Bakers Creek to Town Beach


Episodic flood events in Bakers Creekperiodically flush the entrance, resulting in irregular erosion/ accretion behaviour of the spit.

Interpretation of aerial photography indicatesthat sediments entrained in the ebb tide flowsare transported seaward towards the edge ofthe tidal flats. At the seaward edge of thetidal flats, the influence of the predominantsouth-easterly waves transports the sandback onshore and northward. Further inshore,the transport turns southward towards thecreek entrance, completing a circulation.

Geologically, this area appears to be stillreaching equilibrium following the change inthe course of the Pioneer River more than3500 years ago. The tidal prism of BakersCreek was reduced significantly and thecreek system has been gradually infillingsince. As the catchment is assessed ashaving low potential to export sediments tothe coast (Jones 1987), the source of theaccretion is derived from marine sediments.Most of this accretion would have been fromthe relict delta system soon after the changesto the river; however, it is likely that theinfilling is continuing, although at a low rate.

In Sandringham Bay the estuaries of Sandyand Alligator Creeks behave in a similarmanner. Overall, the system is a complexinteraction of sediment flows undergoingconstant redistribution in response to tidalcurrents, flood events and storm waves. Tothe south of Dudgeon Point, the coast isprimarily comprised of a series of pocketbeaches and it is likely that very little netsediment transport enters Sandringham Bayfrom the south.

Analysis of the available survey data between1971 and 1997 is not conclusive (table 23).The results are variable along the coastalsection and are affected by analysis difficultiescaused by the very flat profiles. In general,the coastline appears to be relatively stablewith a small overall accretion trend of theupper beach, particularly at the southern end.

Commercial sand extraction has beenpermitted in the Bakers Creek estuary and onthe tidal flats adjacent to the creek entrance,although the actual rates of extraction havebeen relatively low compared to the activitiesin the Pioneer River and along Harbour Beach.Any changes to the adjacent beaches as aresult of these extraction works are unable tobe detected from the available survey data.

Harbour Beach southBefore the construction of the harbourbetween 1935 to 1939, Harbour Beachformed a linear beach system from East Pointthrough to Slade Point. The beach is relativelyexposed to the prevailing wave climate andis characterised by strong nearshore tidalcurrents flowing northerly on the ebb andsoutherly on the flood. The continuous supplyof sand from the Pioneer River entrance andthe regular onshore winds have combined togenerate extensive sand dune formations asshown in figure 38.

Tidal flows have a considerable effect onsediment transport along Harbour Beach. Thecharacteristics of the tides in the region resultin a stronger flow in the direction of the ebb.In conjunction with the predominantly south-east wave climate, the net sediment transportis to the north.

At the southern end of Harbour Beach,longshore transport rates are locally veryhigh where the Pioneer River delta attachesto the shoreline. The position of the shorelinefluctuates slightly as shoals merge with thebeach; these features gradually wash out inthe northerly littoral drift.

The southern breakwater of the Mackay OuterHarbour extends across the full width of thenearshore zone where most of the longshoretransport is occurring, and acts as an almost

Southern end of the study area showing Bakers Creek in the background and Shellgrit Creek in the foreground.


complete barrier to the northward transportof sand. Aerial photography shows that theshoreline has accreted immediately updrift ofthe southern breakwater since the harbourwas constructed. The pre-construction coastalalignment has been affected for approximately800m south of the walls.

Following the recent construction of the smallboat harbour extending south of the originalharbour walls, this process is expected to berepeated. In the absence of artificial sandremoval, the coastline would accretesignificantly.

There is potential for a small rate of sedimenttransport to naturally bypass the harbour walls.Numerical modelling has indicated that thepredicted rates of natural bypassing are verylow in comparison with the transport ratesalong the beach; however, if the accretionprocess were left to continue, this rate wouldincrease. This could result in a significantreduction in depth in the harbour entrance.

In the inshore region adjacent to the harbour,the tidal flow characteristics and waveconditions are affected considerably by thebreakwaters. Tidal flows downstream of the

harbour wall are reduced for several hundredsof metres. Upstream flows are acceleratedslightly and diverted offshore close to theharbour walls. The residual tidal flows – thenet movement of water over a full tidal cycle– are therefore directed towards the harbourand with a small offshore component.

Significant quantities of sand have beenextracted from the southern section ofHarbour Beach since the harbour was firstestablished in 1935. The current permitted rateof extraction is up to 70,000m3/a for twosites between East Point and the harbour(GHD 1998). Table 24 provides estimates ofsand extraction over the period 1980 to1992; during this time the average rate ofextraction has been 45,000m3/a.

A condition of the extraction permits requiresthat surveys of the beach and inshore areasin the permit area are undertaken so that theremoval of sand does not cause localisederosion. The analysis of survey data andCOPE profile data indicates that this sectionof coast has remained relatively stable overthe past 25 years (table 25).

Coastal accretion has occurred south of the harbour walls.

Table 25 Survey data analysis for Harbour Beach south (refer figure 32 for location of profiles)


MAC120 2.06 0.71 0.50

MAC122 0.31 0.10 –0.15

MAC124 –1.08 0.42 0.41

Table 24 Estimated sand and gravel extraction rates (103m3)

Source: Gourlay and Hacker Pioneer River Mackay Harbour Board Estimates Total

Site: Upstream Cullen Pioneer Harbour Outer Harbour Pioneer of Hospital Island River Beach to Lamberts Beach River

Year 1969 25* 150.0

1970 25* 30.4

1971 25* 30.4

1972 25* 30.4

1973 25* 120.0 30.4

1974 972* 25* 30.4

1975 25* 30.4

1976 79.9 25* 79.9

1977 119.8 25* 119.8

1978 88.3 322.0 25* 410.3

1979 59.9 150.0 25* 209.9

1980 203.1 150.0 203.0 75.0 353.1

1981 105.4 113.0 54.0 113.0

1982 90.0 90.0 108.0 90.0

1983 122.0 60.0 122.0

1984 167.0 28.0 167.0

1985 70.0 18.0 70.0

1986 69.0 27.0 69.0

1987 52.0 16.0 340.0 52.0

1988 76.0 21.0 76.0

1989 98.4 17.5 98.4

1990 92.4 26.1 92.4

1991 73.4 42.9 73.4

1992 58.0 46.6 58.0

Total: 746.4 622.0 2256.2 815.1 610.0 2436.7

Average: 34.4 20.0 105.9

N.B. * indicates approximate value only.


Figure 45 Aerial photograph, Harbour Beach north to Slade Point

Harbour Beach northNorth of the harbour to Slade Point, thebeaches are similar in character to HarbourBeach south, although the dune systems aremarkedly higher towards the northern end.Apart from the levelling of dunes associatedwith the harbour construction and someisolated commercial sand extraction activity,the area remains intact. Slade Point Reserveand the Mackay Port Authority ConservationReserve have been established to protect theconservation values of the high dune fieldsand freshwater wetlands in this area (figure45 shows the 1997 aerial photograph).

The harbour walls are of sufficient scale tosignificantly shelter the beaches immediatelyadjacent from wave conditions. This effect,in conjunction with the altered tidal current

residuals, results in the tendency foraccumulation of sediments immediately to thenorth of the harbour walls. The accretion ofsediments has been assisted by the placementof significant quantities of dredged sand onthe beach north of the harbour as part of theMackay Port Authority’s capital dredging worksprogram. More than 610,000m3 of mainlysandy material was placed between 1968 and1988. The majority of this material has beentransported northward in the littoral flow, butsome has remained in the deposition zone inthe lee of the harbour walls. Survey data andaerial photographs show a small trend ofbeach accretion for up to approximately 1kmnorth of the breakwater. Information suppliedby the Mackay Port Authority indicates thatundocumented volumes of sand extractedfrom Harbour Beach south were periodicallydeposited downdrift of the northernmostharbour wall.

The survey data show an erosion trend ofabout 19m3/m/a approximately in the centreof the northern section of Harbour Beach(table 26). The upper beach, represented by the4.6m AHD contour, shows a consistent recessionof 0.85m/a. From these results, it is apparentthat the blocking effect of the harbour and theextraction of sand are resulting in continuingdowndrift erosion. A time series of the horizontaldistance between the COPE pole and the 4.6mAHD contour under the COPE upper beachprofile surveys clearly shows the continuingerosion trend (figure 46).

Analysis of the available survey data over theperiod 1971 to 1997 is summarised in table26. The results support the above descriptionof the recent changes to this coastal section.Taken as a whole, the northern 1km of HarbourBeach is estimated to be eroding at an averagerate of more than 7000m3/a.

A previous management practice was to stripvegetation from sections of the dune system

of Harbour Beach north to encourage sand toblow inland. At the time it was anticipated thatdevelopment would eventually extend into thewetland area behind the dunes, which wouldrequire a large volume of fill. It was consideredthat it was significantly less expensive to letnature fill the area with wind-blown sand.

The rate of net longshore sediment transportat the centre of Harbour Beach north has beencalculated as 33,000m3/a. This is close to thecomputed rate south of the harbour and isconsistent with the equilibrium alignment ofthe beach before the construction of the harbour.

A coastline model of Harbour Beach hasbeen established using Unibest CL+, whichsimulates the movement of the averageposition of the shoreline in response tochanges in the longshore sediment transport.In the section north of the harbour, the modelsimulates the downdrift erosion caused bythe blocking effects of the harbour walls, andincludes the sand placement. The simulationwas run for a 50-year period assuming nosand placement occurs north of the harbour.For this case, the model indicates a recessionin the order of 80m at the centre of HarbourBeach north.


Figure 46 Time series of upper beach movements, Harbour Beach north

High dunes at the northern end of Harbour Beach

Table 26 Survey data analysis for Harbour Beach north (refer figure 32 for profile locations)


MAC130 26.84 0.18 0.17

MAC132 18.50 0.46 –0.04

MAC134 –18.61 –0.21 –0.85

Lamberts BeachLamberts Beach is separated from HarbourBeach by a small bedrock outcrop thatintrudes slightly into the longshore sedimenttransport flow (figure 45). Aerial photographyshows a shallow inshore shoal often forms atthe southern end of the beach as a continuationof the main sediment transport pathway.

The upper beach in this section takes the formof a pocket beach alignment between thetwo rocky outcrops at either end, although itsconfiguration is sustained by the throughputof longshore sediment transport. The strongertidal flows and the greater exposure to wavescombine to generate a slightly higher energyregime than that at Harbour Beach. As aconsequence, Lamberts Beach tends to besteeper and has a generally coarser mediangrain-size.

Volume changes on Lamberts Beach arerepresented by only one survey profile. MAC137commences in the centre of Lamberts Beach.The adjacent profiles MAC136 and MAC138have been established on the rocky headlandsat each end of the beach and therefore do notprovide information on upper beach changes.

Analysis of the MAC137 survey data, consistingof six dates, indicates a trend of erosion overthe period 1971 to 1997. Above the –10mAHD contour, the centre of the beach has anaverage loss of more than 10m3/m/a. Applyingthis rate to the effective length of the beach,the average loss has been 6,200m3/a.

Similarly, the upper beach of MAC137 hasreceded by an average of 0.8m/a. This erosiontrend is indicative of the overall downdrifterosion observed on Harbour Beach north.

Slade Point BeachSlade Point Beach faces approximately north-east and has a potential longshore sedimenttransport rate much higher than the actualsupply. As a result, this section has a small-volume sandy upper beach perched on amainly rocky substrate backed by rocky cliffs.The upper beach is episodically supplied bycross-shore sediment transport processes andis dependent on the favourable combinationof high water levels and accretionary waveconditions.

Examination of historical aerial photographyshows that a quantity of aeolian sand onceexisted behind the Slade Point headland(figure 45 shows this in 1997 and figure 47shows this in 1962) .

It is likely that this source of overland sedimenttransport constituted a proportion of thesupply of sand to Slade Point Beach in the past.

Residential development of Slade Point hasnecessitated stabilisation of the dunes,thereby reducing the overall supply of sandto the area.

Bypassing of Slade PointThe continuation of the net northwardsediment transport along Lamberts Beachand Slade Point, driven by longshore wave-induced currents and tidal flows, bypassesthe headland and disperses in a complexpattern. At the headland, sediment transportseparates into two distinct pathways:

� west across the intertidal flats of SladeBay; and

� north-west to a nearshore sand shoalsystem east of Blacks Beach.

The sediment transport across Slade Bay isfurther separated by the channel of McCreadysCreek (figure 38 shows these processesschematically and figure 48 shows the 1997aerial photography from this area).

The bypassing of Slade Point tends to beepisodic in response to the variability of thewave climate and results in a series of sandshoals forming in the lee of the headland.This process is strongly associated with stormwave events. Storms with a predominantlyeasterly component produce relatively lowlongshore transport from Lamberts Beach buta high transport across Slade Bay, thusproducing a net deficit of sand in the lee of

the headland. Events with a mainly southerlycomponent tend to produce the opposite.High transport rates along Lamberts Beachmove large quantities of sediment aroundthe headland, which then accumulate in therelatively sheltered zone as a series ofdistinct banks.

The migration of shoals across the intertidalplatform is further interrupted by lateral tidalflows in and out of the bay and the creeksystem. The shallow braided channel tendsto accentuate the formation of the shoalsalong the outer edge of the tidal flats.

The momentum of the strong ebb tidalcurrents flowing along the eastern shorelineof the headland, in conjunction with wavesbreaking on the rocky shoreline, drive aproportion of the bypassing sediments ontoa system of shoals north of Slade Point.These sandy shoals have formed broadly ona north–south axis and extend across SladeBay almost to Dolphin Heads, (figure 47). Thenorthern shoals, closest to the coast oppositeDolphin Heads, are considerably shallowerand are visible during periods of low water(figure 48).

Grain size analysis of sediments in thesenearshore shoals indicates that the mediandiameter of material on the deeper, southernsection is coarser than that of sediments inadjacent areas. This feature is probably anatural sorting process caused by differentialsettlement of the coarser fractions.


Figure 47 Slade Point, 1962


Figure 48 Aerial photograph, Slade Point to Dolphin Heads

The position and shape of the nearshoreshoals appear to be controlled by tidal flowsas shown in figure 20, although on occasionsstorm wave conditions move this materialonshore towards Dolphin Heads to rejoin thelittoral system. Analysis of hydrographicsurvey data shows that the landward edge ofthe northern shoal has been slowly migratingonshore since the first available survey datain 1977. The survey data also show that thenearshore shoal has increased in volume atthe northern extremity over the past 20 years.

It is likely that the volume of the northernsection of the shoals is fluctuating over arelatively long time scale, as the shallowersection builds in height and then episodicallybreaks away to migrate onshore. This thereforehas implications for the downdrift beacheswhich episodically receive additionalquantities of sand. The limited data on thehistorical changes in this area do not allow anaccurate estimate of this process to be made.

Slade Point western shoreThe majority of the sediment transport acrossSlade Bay is along the outer margin of thetidal flats, influenced by the predominantlysouth-easterly wave climate. Some of thesebypassing sediments are transported onshoreand across the tidal flats by wave energyapproaching from the north-easterly sectorand waves refracted around the headland.

A proportion of this onshore transport isalong the western shore of Slade Pointtowards the entrance of McCreadys Creek.Due to the sheltering from wave energy andthe relatively weak tidal currents, themorphology of this area tends to changerelatively slowly under ambient conditions.The inshore zone generally comprises a rockysubstratum overlain by a thin veneer of sandand patches of mud.

Historical aerial photography shows a seriesof distinctive sand shoals moving across theinshore zone towards the entrance ofMcCreadys Creek. Through examination ofthis sequence, estimates have been made ofrates of travel of these shoals. An indicativetime scale of 25 years has been estimatedfor travel of a shoal along the western shoreof Slade Point.

The inshore zone has shown significantvariability in response to the episodicsediment supply. A stand of mangroves hasgrown approximately halfway along theshoreline. The presence of the mangrovesindicates that this section is relativelysheltered from incident wave energy and ebbtidal flows from McCreadys Creek.Occasionally the mangroves are smotheredby the passage of a sand shoal, resulting in ashort-term dieback.

The variability in sediment supply along thewestern shore of Slade Point is related to theepisodic bypassing of Slade Point and thefluctuations of the ebb tidal channel. As aresult, the system is vulnerable to high-energy wave events such as cyclone swellrefracting around the headland, and north-easterly storms, which generate bursts ofhigh-rate, short-term longshore transport.Due to the variable distribution of sedimentnear the shoreline, differential longshoretransport during storms results in erosion insome sections and accretion in others. Thiseffect is more apparent further into theembayment, where the primary channel ofMcCreadys Creek is close to the shoreline.

The sediment transport along the westernshore of Slade Point appears to beapproximately balanced by the outflow drivenby the ebb tidal currents from McCreadysCreek. Sediments are transported seawardsin the high velocity flow to rejoin the littoraltransport along the margin of the tidal flats.

Analysis of hydrographic survey data iscomplicated by the variability caused (table27) by the movement of the shoals. Overalltrends in the data indicate that the volume ofthe tidal flats in this area is relatively stable.The shoreline position, determined fromaerial photography, has also been relativelystable. In geological terms, it appears thatthe embayment has reached an approximateequilibrium and there is no clear evidenceindicating a recent erosion trend.

Property owners have constructed a series ofrock walls along the western shore of SladePoint to protect residential allotments fromepisodic erosion. Close to the entrance toMcCreadys Creek, the walls also have theeffect of training the primary tidal channel.

Blacks BeachThe alignment of Blacks Beach and theconfiguration of the tidal flats are controlledby the bedrock outcrops of Slade Point andDolphin Heads. Relatively recent deposition ofsediments, sourced mainly from the PioneerRiver, has formed the barrier system on thepresent-day alignment following the Holocenetransgression. This has also resulted in theformation of a low-lying area behind the barriercomprising the catchment of McCreadys Creek.

Blacks Beach is more northerly facing beachthan any of the other open coast beaches inthe Mackay area. This is in response to thesheltering effect of the Slade Point headlandrelative to the predominant south-easterlywave climate and the complex pattern ofsediment transport across Slade Bay. At thenorthern end of Blacks Beach, the beachnarrows and is close to the rock cliff behind.The high northerly potential longshore transportrate in this section is greater than the availablesupply, preventing the establishment of anupper beach.

Along the southern end of Blacks Beach, thenet longshore transport is directed weaklysouthward towards the entrance of McCreadysCreek. The ebb tidal flow of McCreadys Creektends to transport this material back offshoreto rejoin the wave-driven sediment flowsalong the margin of the tidal flats.

The southern end of the beach terminates as aspit forming across the entrance of McCreadysCreek. The McCreadys Creek estuary systemhas accumulated a large quantity of sand andsilts, resulting in extensive areas of supratidalflats and intertidal wetlands.

The main sediment transport pathway acrossSlade Bay is along the outer margin of thetidal flats; approximately halfway alongBlacks Beach, a distinct convex bulge in thecoastal alignment can be seen where thissediment transport pathway reattaches tothe shoreline (see figure 48).

The net longshore sediment transport rate at the northern section of Blacks Beach hasbeen estimated as 28,000m3/a (table 20). As the survey data between Slade Point andDolphin Heads do not show a clear trend ofaccretion, it may be inferred that the differencebetween this rate and the longshore sedimenttransport rate at Lamberts Beach is equal tothe rate of transport to the nearshore shoals.This rate is therefore approximately 5000m3/a.It is likely that these sediments accumulateon the nearshore shoals and periodically re-enter the littoral system at Dolphin Heads asa series of sand slugs.


Table 27 Survey data analysis for Slade Bay (refer figure 32 for profile locations)



MAC147 15.99 insufficient data



An examination of survey data and aerialphotographs indicates that the location ofthe sediment transport reattachment pointnear the centre of Blacks Beach, and hencethe coastline bulge, varies considerably. Thisvariation is related to variability in the netlongshore transport rate, primarily in responseto individual storm events or sequences ofstorm events. During storm events, high waveenergy penetrates into the embayment,generating high sediment transport rates thatreduce the overall volume of material,subsequently tending to move the shorelinebulge southward.

The coastal alignment in the middle of BlacksBeach therefore has a large potential forvariability (figure 49 shows the variation ofhistorical shorelines, derived from aerialphotography). Rock walls have been constructedon some sections of the upper beach to protectfreehold properties from erosion; these haveartificially constrained the coastline.

It is apparent that the coastal alignment of thecentral section of Blacks Beach was relativelyadvanced when property boundaries were firstsurveyed. In the absence of the rock walls, thenatural position of the coastline would tendto fluctuate landward of these boundaries.Since the establishment of the first residentialproperties along Blacks Beach before the1950s, the area has suffered erosion. Thismay be explained by two factors:

� the long-term, natural fluctuations of thecoastline in response to the variability ofsediment transport across Slade Bay; and

� the presence of the rock walls on the upperbeach, which have the effect ofdiscouraging the natural rebuilding of thebeach and dune system.

Analysis of survey data over the period 1977to 1997 show significant variations due tofluctuations in the seabed levels across theintertidal flats, particularly the outer section(table 28). These correspond to the passageof shoals through the area. Key points maybe summarised as follows:

� the profiles of the beach sections aroundthe centre of Blacks Beach are highlyvariable. The profile at MAC157 (figure 32shows the location), which is close to thesediment transport reattachment point,shows significant phases of accretion anderosion around the high water markalthough the location of the toe of thedune is relatively stable;

� to the south, survey data at MAC156 show aclear trend of recession. The toe of the duneat this point has been receding at an annualaverage of more than 1m since 1977;


Figure 49 Historical shorelines, Blacks Beach

� at MAC158 and MAC159, adjacent to thelong section of rock wall, the upper beachshowed a recession of more than 20mbetween the 1978 and 1979 surveys andhas been accreting gradually since. Thiserosion can be attributed to tropicalcyclone Kerry in March 1979;

� the profiles at the southern end of BlacksBeach, lines MAC152 to MAC155, areconsiderably affected by seabed fluctuationscaused by the passage of shoals throughthe area. Analysis of these data areinconclusive although it can be inferredthat the shoreline has been relativelystable over the past 20 years; and

� at the northern end of Blacks Beach, linesMAC160 and MAC161 show a trend oferosion over the nearshore profile to the–5m AHD contour. The upper beach in thissection is at the base of the rocky cliff.

Dolphin Heads and EimeoThe net northward sediment transport alongBlacks Beach passes through to BucasiaBeach and Shoal Point via Dolphin Headsand Eimeo Beach. In addition, the nearshoresand shoals off Blacks Beach have a slowonshore feed back into the littoral system.The reattachment point appears to be in thevicinity of Dolphin Heads (figure 50).

The beaches to the west of Dolphin Heads arerelatively exposed to wave energy from theeast and north-east. The rate of longshoresediment transport is generally higher thanthe available supply of sand, preventing theformation of a sandy upper beach. The rockysubstrate is often exposed and the intertidalarea is strewn with small boulders and cobbles.Further west along the Dolphin Heads shorelineis a low dune system, which is formed mainlyby wave action. Excavations in this area haverevealed the presence of large cobbles belowthe surface that have probably beentransported from the headland by the actionof storm waves. This indicates the potentialfor the penetration of high wave energythrough this section.

A number of short rock groynes have beenconstructed on the rocky intertidal platform inan attempt to encourage the sedimentation ofsandy material near the shoreline. In addition,low rock walls have been constructed to halterosion along the seaward boundaries offreehold properties.

Eimeo Beach has formed into a barrier systembetween Dolphin Heads and Eimeo headlandas part of the net northward longshore sedimenttransport regime. A small tidal waterway drainsthe low-lying area behind the beach into thesouthern end of the embayment.

Eimeo Beach features a relatively wide areaof tidal flats at the southern end, narrowingat the northern end. This area comprises athin layer of sand overlying a rocky platform;patches of bedrock outcropping can often beseen. The main sediment transport pathwayalong Eimeo Beach is through the intertidalarea where an inshore bank forms in the leeof the Dolphin Heads and interacts with thetidal flows from the creek. The intertidal bankscan vary considerably in shape in responseto an irregular supply of sand bypassing theheadland.

The presence of the bedrock platform extendingfrom Dolphin Heads and the volume of sandin the intertidal banks influence the alignmentof Eimeo Beach, particularly at the southernend. The volume of this section is dependenton the configuration of the inshore sandbanks


A series of rock walls have been constructed at BlacksBeach.

Blacks Beach 1997Blacks Beach 1962

Table 28 Survey data analysis for Blacks Beach (refer figure 32 for location of profiles)


MAC152 –0.95 –0.24 –0.27

MAC154 48.62 0.10 –0.42

MAC155 0.22 0.77 0.30

MAC156 –22.51 –1.18 –1.80

MAC157 8.45 –0.07 0.97

MAC158 7.60 0.31 –0.53

MAC159 –2.32 –0.15 –0.48

MAC160 –2.36 –0.20 –0.49

MAC161 –6.05 –0.03 0.08


Figure 50 Aerial photograph, Dolphin Heads to Shoal Point

and can be prone to erosion in high waveenergy and water level storm events.

Rock walls have been constructed on theseaward boundary of several properties atthe end of the spit as protection fromdamage from storm waves.

Eimeo Beach volumetric changes have beenderived from five hydrographic surveys ofsurvey line MAC167 between 1978 and 1997.

This profile extends offshore from near thesouthern end of the beach. The surveyanalysis indicates a continuing trend of erosion,although it is probably related to cyclicfluctuation with a time scale longer than the20 years of survey data. The average loss ofvolume above the –5m AHD contour hasbeen 7.5m3/m/a; however, there appears tobe little continuing change in the position ofthe upper beach.

A proportion of the sediment bypassing Eimeoheadland is transported along the western

shore of the headland towards the entrance ofEimeo Creek. In a similar process to that seenon the western shore of Slade Point, thistransport is episodic in nature and the shorelineoften shows significant fluctuations as slugsof sand move through. Freehold propertiesfront the majority of this western shorelineand a number of low rock walls have beenestablished for protection against sequencesof erosion. Some parts of this coastline arerelatively low-lying and prone to flooding.

An analysis of historical shorelines showsthe potential for large changes in coastlineposition through this western shoreline, asillustrated by figure 51.


Figure 51 Historical shorelines, Dolphin Heads and Eimeo (photography captured 17/8/1993)

Bucasia BeachThe extensive barrier system of Bucasia Beachshows a morphology similar to that of BlacksBeach, although the embayment is not asdeeply indented as Slade Bay (figure 50). Thewide tidal flats in the lee of Eimeo headlandnarrow to form a gently curving sandy beachat the northern end towards Shoal Point. Atthe southern end, Eimeo Creek drains thetidal wetlands behind the coastline.

Sand bypassing Dolphin Heads and Eimeodisperses across the embayment in a complexpattern. The bypassing sediment flowgenerated by the action of waves and tidalcurrents interacts with the outflow of EimeoCreek to form a sequence of intertidal banks.These banks are driven across the bay andonshore by wave action. In comparison withSlade Bay, there is relatively more wavepenetration into the intertidal area, whichresults in a wider sediment transport pathway.The pronounced shoreline bulge seen onBlacks Beach at the point of attachment isless evident on Bucasia Beach, althoughhistorical shoreline data show potential forsome changes at the southern section.

At the southern extremity of Bucasia Beach, aspit has formed across the entrance to EimeoCreek. The growth of the spit appears to beregulated by southward longshore transportfed from shoals moving onshore from theintertidal flats. The location and configurationof the creek entrance and the primary ebbtide channel have remained fairly stable overthe past 25 years, although this area couldbe subject to overtopping during severestorm conditions.

Bucasia Beach has formed as a wide sandybeach with a well-developed dune system.The nearshore area is relatively shallow andfeatures two small rocky islets offshore fromthe northern end of the beach. The coastalalignment of this section of the beach isinfluenced by the sheltering effect of thesouthernmost islet, and it forms a slightconvex shape approximately 1.6km south of Shoal Point.

Geological evidence indicates extensivetransport of sand past Shoal Point into SandBay and northward into the BlackwoodShoals area (Jones 1987). Analysis of surveydata from 1977 to 1997 is summarised intable 29. The data show a consistent trend ofaccretion throughout the Bucasia Beach section.

The net longshore sediment transport rate atthe northern section of Bucasia Beach hasbeen estimated to be 20,000m3/a (table 20).The analysis has shown that the rate ofsediment transport into the embayment is

higher than the rate at which sediment istransported northward past Shoal Point. Thisresult is consistent with the observedaccretion trend throughout Bucasia Beach. Itis apparent that the embayment is yet toreach equilibrium in response to the changedconditions that occurred some 3500 yearsago, when the Pioneer River changed courseto its present alignment.


Table 29 Survey data analysis for Bucasia Beach (refer figure 32 for location of profiles)


MAC172 8.98 0.52 0.28

MAC173 2.08 0.60 0.29

MAC174 7.57 0.78 0.38

MAC175 17.59 0.77 0.76



MAC178 14.62 0.78 0.36

MAC179 11.82 0.05 –0.13

MAC180 9.22 0.03 –0.43

IntroductionCoastal resources in the Mackay region arehighly sought after for competing usesincluding residential, commercial, tourismand recreation. Effective management isnecessary to ensure that the natural valuesand attributes of the coast are preservedwhile economic development and expectedrates of population growth areaccommodated.

In the past, development within the coastalzone has often been undertaken with limitedunderstanding of natural processes, and inmany cases this has led to inappropriate use ofcoastal lands. Uncontrolled urban development,recreation and tourism activities can lead tothe degradation of the natural values of thecoast. Encroaching infrastructure anddevelopment result in increased land values;however, they can also result in a demand forengineered coastal protection works such asrock walls. The primary coastal managementissue considered in this study is theinteraction of various land uses in the regionwith hazards related to coastal processes,such as erosion and storm tide flooding.

It is important to manage existing and futuredevelopments to ensure that they do notcause any significant or unacceptable increasein hazard or risk of damage by adverseinteraction with coastal processes. Thisapproach supports the general principle ofthe sustainable use of coastal resources andis an essential component of sound coastalmanagement. Additional considerationsinclude:

� the sustainable use of sand and gravel resources;

� the conservation of critical habitatsand areas of important remnantvegetation; and

� protection of sensitive coastalwetland areas.

Coastal hazardsCoastal hazards are the result of developmentspoorly located with respect to prevailingcoastal processes. A number of hazards havebeen identified in the Mackay coastal region,including:

� short-term beach erosion associated withstorm events;

� coastline recession;

� recession related to climate change andsea-level rise; and

� storm tide flooding.

As a general principle, it is desirable to avoidthe exposure of communities to coastalhazards in order to minimise economic andsocial costs. Often the most cost-effectivemanagement of coastal hazards is achievedthrough the establishment of buffer zonesalong the shoreline.

The Coastal Protection and Management Act1995 also provides for buffer zones in the formof erosion prone areas, which are beachfrontlands intended to remain free of development.Erosion prone areas established under the Actare primarily intended to allow for fluctuationsin coastline position caused by naturalerosion processes. These buffer zones arealso important for the preservation of naturalcoastal processes and the establishment of anatural barrier against storm tide inundation.Erosion prone area widths for the Mackay regionhave been available for many years and arethe basis for much of the EnvironmentalProtection Agency’s coastal managementactivities. Information developed as part ofthis study has been used to review and reviseerosion prone area widths in the region.

Erosion prone area widthsThe formula adopted by the EnvironmentalProtection Agency to determine widths oferosion prone areas for a particular sectionof beach is:

E =[(N x R)+ C + G]x (1 + F) + D

where:

E is the erosion prone area width (m)N is the planning period, taken as 50 yearsR is the rate of long-term recession (m/a)C is the short-term erosion (m)G is the erosion due to sea-level rise

associated with the greenhouse effectF is a factor of safety, taken as 40 percentD is the dune scarp component (m)

The components of erosion prone area widthcalculations are shown graphically in figures52 to 54. It is noted that the values of N andF are relatively subjective quantities. Thevalues of 50 years and 40 percent, respectively,have been selected to conform with previouscalculations of erosion prone area widths.

The calculation of D, the dune scarpcomponent, is required to allow for slumpingof the erosion scarp above the wave run-uplevel. This is generally required becausenumerical methods for calculating the short-term erosion profile typically do not provideinformation above the water level.

A review of existing erosion prone areawidths has been undertaken for the Mackayregion. This review has been undertaken foropen coast sections only. Erosion proneareas within estuaries are defined as a line40m landward of the mean high water markat spring tides or the plan position of thehighest astronomical tide, whichever providethe greatest erosion prone area width.

Estimates for short and long term erosion havebeen made in areas where rock walls currentlyexist. Walls constructed seaward of privateproperties principally for the purposes ofproperty protection are generally notconsidered as public assets even thoughthey may be partially on public land. In termsof long term coastal recession, it cannot beassumed that existing walls will be maintainedto the standard required for coastal protection.For this reason, nominal recession valueshave been used at some locations.

16 Coastal management


In locations where rock outcrops exist on abeach, it is anticipated that erosion will belimited to the section seaward of the rockextent. The maximum erosion prone areawidth in this area is given and is annotatedwith an asterisk (*).

The following discussion provides backgroundinformation on the components making upthe erosion prone area calculations. KinhillCameron McNamara (1994) also provide ageneral discussion on the determination ofcoastal buffer zone widths.

Short-term erosionStorm erosion is caused by the exposure ofthe upper beach and dune to high waveconditions and elevated water levels. Duringnormal conditions, the surf zone is limited toa position around the high water mark.However, the combined effect of storm surge,wave set-up and wave run-up allows stormwave energy to reach higher levels andusually results in the erosion of the upperbeach and the transport of sediments offshore.

Generally, along a continuous beach theshort-term erosion of the upper beach isbalanced by a corresponding accretion in thenearshore zone. During calmer conditionsthe sand is gradually moved back onshoreand, in conjunction with aeolian processes,rebuilds the upper beach.

The effects of cross-shore erosion can oftenbe exacerbated during storm events byrelative differences in longshore transport.Where the beach system is discontinuous,for example in the vicinity of a groyne orheadland, these effects can be significant.

Numerical simulation of short-term beacherosion has been undertaken using the SBEACHmodelling system developed by the UnitedStates Army Corps of Engineers CoastalEngineering Research Center (Larson andKraus 1989). This model provides a semi-empirical approach to determine time-dependent cross-shore sediment transportprocesses for an arbitrary beach profile.SBEACH has been verified against a variety ofphysical model and field data and has beenused extensively worldwide in planning studiesand design of beach nourishment projects.

Guidance on the selection of the empiricalparameters used for SBEACH input data isgiven by Larson and Kraus (1989). The sedimenttransport rate coefficients K and EPS are theprimary calibration parameters. They werechosen using wave, water level and COPE(Harbour Beach) beach profile data for thetropical cyclone Joy event in 1990. The finalparameter values used in the SBEACHmodelling are stated in table 30.

The boundary conditions required for SBEACHmodelling consist of a pre-storm beach profileand a time series of water levels and waveconditions. Typical hydrographs of wave heightand water level were developed usingpredicted tide data and information fromvarious numerical modelling studies. Waveperiods and directions were determined fromthe analysis of recorded and hindcast extremewaves at the Bailey Islet site.

Peak design storm values were selected fromthe information on joint probabilities of wavesand water levels. The approach is similar tothat taken in previous studies, using thefollowing criteria:

� the design storm tide level is consideredmore critical to the overall sensitivity ofresults than the design wave height;

� a design water level condition is chosensuch that there is an estimated 40 percentchance of being equalled or exceeded overa 50-year planning period;

� assuming a Poisson distribution ofoccurrences of extreme events, the designwater level condition corresponds to a100-year average return interval (ARI);

� the adopted 100-year ARI storm tide levelfor the Mackay area is 4.1m AHD;

� for the purposes of generating water levelhydrographs, the storm tide is assumed tocomprise a 1.8m storm surge in conjunctionwith a 2.3m AHD tide (corresponding tomean high water springs); and

� the median extreme wave height (50 percentnon-exceedance) corresponding to the 100year ARI water level is chosen from the jointprobability analysis. For a location offshorefrom Mackay, this Hsig value is 5.2m.

SBEACH modelling was undertaken for 10locations in the study area (figure 52provides an example of an SBEACH modelrun at Harbour Beach showing the pre- andpost-storm beach profile). Results for stormerosion of the 4.6m AHD contour are providedin table 31. The 4.6m AHD contourcorresponds to the design storm tide waterlevel plus the typical wave run-up level.

The SBEACH model runs for the area betweenBakers Creek and the Pioneer River show thatthe dunes are likely to be overtopped by thedesign storm. The simulated recession at the4.6m AHD level is computed to be a relativelysmall value, typically in the order of 5m. Theactual effect is estimated to be a recession of30m, i.e. the width of the dune, due toovertopping. A storm erosion value of 30mhas therefore been adopted for this section.

Dune scarpingA dune scarping component is included inthe erosion prone area calculation to allowfor slumping of the dune above the totalwater level of 4.6m AHD. It is assumed thatthe dunes will slump to a 1:3 slope (figure53). As the dunes in the Mackay region varyin height from about 5m AHD to more than15m AHD, the values adopted for the dunescarping component D are typically in theorder of 5 to 20m.


Table 31 Storm erosion results, SBEACH (refer figure 32 for profile locations)

Survey profile Shoreline (4.6m AHD contour) Volume to 0m contour(m/a) (m3/m/a)

Bakers Creek–Shellgrit Creek MAC108 4.6 not applicable

Far Beach MAC108 4.6 not applicable

Town Beach MAC112 5.1 not applicable

East Point MAC118 25.3 35.9

Harbour Beach south MAC122 15.1 16.1

Harbour Beach north MAC134 8.5 49.8

Lamberts Beach MAC137 25.9 165.5

Blacks Beach north MAC159 16.0 128.9

Eimeo Beach MAC167 7.3 0.3

Bucasia Beach MAC178 15.3 41.6

Table 30 SBEACH parameter values

Description Name Value

spatial grid step (m) DXC 2

time step (min) DT 30

sediment transport rate K 2.0 x 10–6

coefficient (m4/N)

slope dependent transport EPS 0.01rate coefficient (m4/sec)

wave decay coefficient KAPPA 0.06

foreshore slope FSL 0.3

water temperature (°C) TEMPC 27

depth corresponding to the land- DFS 0.2ward end of the surf zone (m)

median grain size (mm) D50 site-specific

Coastline recessionCoastline recession can be the result of long-term geological processes such as sea-levelrise, or medium-term effects associated withthe natural variability of coastal systems suchas low frequency changes in the storm waveclimate and fluctuations of river entrances.

Assessment of continuing erosion trends isgenerally undertaken using analysis ofhydrographic survey data and aerialphotography in conjunction with a review ofthe local geomorphology. The objective isgenerally to determine the maximum extentof recession that may occur in a 50 yearplanning period. In the case of a medium-term variability, the maximum recession maybe reached before the end of the period.

Long term shoreline changes may result in astable coastline, however current evidencemay indicate that a particular beach is erodingor accreting. In situations where the beach isstable or accreting, a nominal long termerosion component has been adopted.

Where sufficient data are available, a sedimentbudget may be calculated to determine a volumetric loss (or gain) of material. A sediment budget deficit is converted into a horizontal recession through a linearrelationship based on the simplifiedgeometry of the beach profile (figure 54).

Based on the assumed profile, the annualerosion quantity can be related to the annualrecession by the following relationship:

Qe = ( R x h1 ) + 0.5 ( R x h2 )= R ( h1 + 0.5h2 )

� R = Qe / ( h1 + 0.5h2 )

where Qe = erosion quantity (m3/m/a)

h1 = height of frontal dune abovebreak in profile (m)

h2 = depth below break in profile atthe point where no changesoccur (m)

R = long-term erosion rate (m/a)

This approach assumes that the volumetricchanges are accommodated evenly along thebeach. In reality, the coastline planform isaffected in a complex way depending on thegeological controls and the rates of sedimenttransport. In some cases, useful informationcan be gained from a coastline model thatsimulates the behaviour of beach systemssubject to variable sediment supply.

A coastline model was established forHarbour Beach using Unibest CL+ (version5.01) (Delft Hydraulics 1999) to assess thedowndrift effects of the harbour walls andthe sand extraction activities. Although the

modelling approach is limited by a numberof assumptions, the model provides a goodindication of potential future changes for thesection of Harbour Beach north of the walls. Theapplication of this model is discussed below.

The long-term behaviour of some coastalsections is too complex to be represented bythe Unibest CL+ model. The processes at Far,

Town and Blacks Beaches are affected bycross-shore sediment transport, which cannotbe represented in a one-line model. In thesecases, estimates of long-term changes havebeen derived from an analysis of historicalvariations (table 32 provides the results ofthe analysis of potential coastline recessionwithin a 50 year period).


Figure 52 SBEACH results for Harbour Beach (MAC122)

Figure 54 Horizontal recession for Blacks Beach

Figure 53 Dune scarp component of coastal recession

The assessment of coastline recessionassociated with climate change-induced,sea-level rise has been calculated separatelyfrom other estimates of coastline recession.

The potential impacts of climate change onthe incidence of severe storms over the 50-year planning period are difficult to quantify.Even modest changes in tropical cyclonefrequency and intensity would be difficult toseparate from the natural variability. Due to theuncertainty of likely changes, no additionalexamination of the effects was undertaken as part of this study.

At the time of writing, the best estimate ofprojected global sea-level rise over the 50-year planning period is a value of 0.2malthough estimates range up to 0.5m (figure 15).The Beach Protection Authority has adopteda more conservative value of 0.3m to assessthe potential impacts of sea-level rise.

The Bruun Rule (Bruun and Schwartz 1985) iscommonly used to determine indicative ratesof recession for sandy beaches subject tosea-level rise. The calculation assumes thatthe beach maintains a dynamic equilibriumprofile that is directly related to the mean

sea-level. Thus there will be an increase inthe level of the nearshore seabed in responseto the increase in mean sea-level. Accordingly,an erosion of material from the upper beachmaintains the equilibrium beach profile.

The formula for the Bruun Rule is a simplecontinuity relationship where the volumeassociated with the horizontal recession of thecoastline is equal to the volume associatedwith the vertical increase in the bed levelover the active beach profile. This is describedby the following equation:

G x Z = a x B

where G is the recession associated withsea-level rise

Z is the vertical extent of the activeprofile

a is the sea-level rise

B is the width of the active profile

The active profile is considered to extendfrom the top of the primary dune to the depthof closure, which is the seaward limit ofsignificant cross-shore sediment transport.The closure depth throughout the Mackay

region has been derived from considerationof wave climate and sediment properties.The adopted value for beaches in the Mackayregion is typically –10m AHD.

Results of the analysis of potential coastalrecession associated with sea-level rise forthe cases where the Bruun Rule can beapplied are provided in table 33.

In many cases, the effects of sea-level rise onthe coastal alignment are more complex thanthat described by the equilibrium profileapproach of the Bruun Rule and the overallsediment budget needs to be taken intoaccount. Complicating factors include:

� the sediment sink effects of estuaries andembayments;

� the significant cross-shore processesoccurring on the tidal flats; and

� the supply of sediments from the PioneerRiver.

The common factor is the assumption thatthe nearshore seabed level will accrete inresponse to an increased mean sea-level.This is also the basis of the Bruun Rule.

Even where no recession due to profileadjustment is likely to occur, the rise in waterlevel will cause the shoreline to move up theprofile. There will therefore be a generallandward movement of the wave run-up limit,the line of vegetation and the toe of theforedune. The recession in this case is simplydetermined from the foreshore slope.

Response of tidal flats tosea-level riseThe assumptions of the Bruun Rule aregenerally not simply applied in the casewhere the beach is part of a system of widetidal flats. In this case the behaviour of thebeach is not completely connected with thetidal flats and the simple assumption of aprofile adjustment across the entire profilecannot be applied. This is of importance inthe Mackay region because of the prevalenceof extensive tidal flats throughout the area.The calculation of the G component for theerosion prone area calculations for coastalsections that include tidal flats requires anestimate of a modified depth of closure. Thisis discussed further in the following chapter.

Within the Pioneer River estuary, a sea-levelrise associated with the greenhouse effectcould result in a corresponding net accretionof the river bed throughout the tidal reaches.While the system response would be affectedby the present-day morphological behaviour ofthe river, it is likely to result in some reductionin the rate of export of sediments to the coast.


Table 32 Estimates of potential long-term coastline recession

Location Coastline recession in 50 years (m) Comment

Bakers Creek–Shellgrit Creek 20 based on historical fluctuations

Far Beach 50 based on present recession rate

Town Beach 10 nominal value

Harbour Beach south 10 nominal value

Centre of Harbour Beach north 80 derived from coastline model

Lamberts Beach 35 derived from coastline model

Blacks Beach south 20 based on historical fluctuations

Blacks Beach north 40 derived from historical coastlines

Eimeo Beach 10 based on present recession rate

Bucasia Beach 10 nominal value

a A modified depth of closure has been used for beaches fronted by wide tidal flats. The discussion in the coastalmanagement section provides further details.

b The section of Harbour Beach adjacent to East Point is influenced by the onshore transport of sand from thePioneer River entrance delta. The likely climate change recession value in this section is zero.

c The Blacks Beach profile is influenced by nearshore sand shoals that are considered independent of the beach system.

Table 33 Potential coastal recession associated with sea-level rise

Location Survey profile Depth of closure (AHD) Coastal recession (m)

Bakers Creek–Shellgrit Creek MAC104 0 ma 5

Far Beach MAC108 1 ma 14

Illawong Park MAC112 0 ma 21

Harbour Beach southb MAC122 –10 m 20

Harbour Beach north MAC134 –10 m 7

Lamberts Beach MAC137 –10 m 9

Blacks Beach north MAC159 –3 mc 21

Eimeo Beach MAC167 –7 m 37

Bucasia Beach MAC179 –6 m 13

Sea-level rise due to climate change

Storm tide hazardIn terms of risk of storm tide inundation, theMackay region is one of the most vulnerablesections of the Queensland coast (Harper1998). Numerical and statistical studies ofthe joint probability of storm surge and tide(BPA 1985) have indicated that potentialstorm tides in excess of 1m above thehighest astronomical tide level (HAT) couldoccur on average once every 100 years.

Only two category four cyclones crossed theQueensland coast in the 20th century; one ofthese passed directly over Mackay in 1918.The resultant storm tide of approximately 2mabove HAT (5.47m AHD) caused extensiveflooding and damage to infrastructure. Thestorm tide flooding and the followingfreshwater flood in the Pioneer Rivercontributed to the loss of 31 lives.

Because of the low-lying nature of manyparts of the region, a number of residentialareas are prone to coastal flooding (figure 55shows the indicative area south of the PioneerRiver that would be affected by a storm tideof 5m AHD). The coastal areas of SouthMackay and East Mackay are clearly at riskfrom storm tide inundation.

Management of coastal areas, particularlythe dune systems, is important to minimisethe hazard of storm tide inundation. Themaintenance of a well-vegetated dune systemprovides a natural barrier to extreme waterlevels and helps to absorb storm wave energy.This is particularly important at Town and Far Beaches.

Coastal management optionsIn some isolated cases within the Mackayregion, property and infrastructure arethreatened by coastal erosion. This isprimarily the result of poor land use planningand usually can be attributed to a limitedunderstanding of natural coastal processesat the time the land use decisions weremade. Often such decisions were made inthe order of 50 to 100 years ago. Theappropriate management responses dependon the nature of the erosion and, ultimately,the overall cost.

Financial responsibility for protecting privateproperty rests with the property owner. Incases where public assets, including beachamenities, are threatened, the localgovernment is responsible. Some beachprotection works carried out by localgovernments and approved by theEnvironmental Protection Agency normallyattract a State Government subsidy.

Management options that can be used toprotect properties from coastal erosion include:

� retreat through the acquisition of land or relocation of infrastructure;

� beach nourishment or beach scraping;

� dune conservation works;

� sand bypassing systems to ensure thatnatural sediment supply continues acrossartificial barriers;

� protective structures such as seawalls;

� beach control structures such as groynes,or offshore breakwaters; and

� configuration dredging to influence tidalflows and wave transformation patterns.

A number of coastal protection works havebeen undertaken in the Mackay region,primarily to protect freehold property andpublic infrastructure from coastal erosion.Rock walls have been constructed alongopen coast sections of Far, Town and BlacksBeaches. Lower-grade rock revetments havebeen constructed on the lee side of the major

headlands, Slade Point, Dolphin Heads andShoal Point. In many cases, althoughsuccessful in reducing coastline recession,these walls have significantly affectedadjacent beaches.

Retreat optionThe option of removing or relocatinginfrastructure back from the threat of coastalhazards accords with the EnvironmentalProtection Agency’s policy of establishingcoastal buffer zones. Assuming sufficientwidth is allocated to allow for the naturalfluctuation of the coastline, this option isoften the most cost-effective over the longterm as it requires little continuing maintenance.

In cases where freehold or leaseholdproperties are adjacent to the high watermark, acquisition can have the added benefitof improving public access to beaches.Removing or relocating dwellings back fromthe beachfront can also be effective inreducing storm tide hazard.


Figure 55 Area south of Pioneer River affected by 5m AHD storm tide

The retreat option is generally expensive andis sometimes unpopular with landowners, butin isolated cases a full or partial acquisitionmay be the only realistic solution. Whereproperties are of sufficient size, it may bepossible to relocate buildings and otherimprovements landward within the property.

Beach managementA number of options are available to maintainbeach systems as a natural buffer againstshort-term erosion and storm tide flooding.Where specific upgrading of beaches isrequired, the Environmental ProtectionAgency generally favours beach nourishmentas the most effective option.

Beach nourishment involves the mechanicalplacement of sand that is usually sourcedfrom inactive sand reserves either offshore oron land. Sand may be placed directly on theupper beach or in the lower part of the beachprofile using a technique known as nearshorenourishment. Nourishment works generallyrequire the use of dredges and other expensiveequipment. Costs can range from the order of$5/m3 to more than $30/m3, depending onthe type of equipment required, the source ofthe nourishment sand and the quantity ofsand involved. In addition, a nourishmentmaintenance program is usually requiredover the longer term.

An alternative form of beach nourishment isthe mechanical movement of sand from onepart of the beach system to another,commonly known as sand scraping. This canbe undertaken relatively cheaply usingconventional earthmoving equipment. Whilethe technique is limited in that the overallbeach volume does not change, it is useful insome situations to build up the upper beachsections using sand from nearshore areas.

Sand scraping is a useful technique in regionssuch as Mackay, where the large tide rangeprovides good access to nearshore areas atlow water. The technique is also likely to becost-effective because of the relatively slowchanges in coastal morphology through much of the region.

Continuing dune conservation works tomaintain the sand reserve in the dune systemare an essential component of coastalmanagement. The dunes are generally theprimary barrier against storm tides and areeffective in absorbing wave energy duringstorms. Typical dune conservation worksinclude revegetation and the construction ofpedestrian control fences and access tracks.

Where littoral longshore transport is interruptedby works such as river entrance training walls,dredged channels or breakwaters, an artificialsand bypassing system may be beneficial inpreventing downdrift erosion. Bypassingsystems can take on a variety of forms andare usually based on hydraulic or mechanicalsand-pumping plant. Such systems aregenerally quite expensive to construct andoperate. As they are usually required only tocompensate for the interruption of littoralprocesses by large-scale coastal infrastructure,the implementation of artificial sandbypassing systems should be considered inthe overall costs of the asset.

Coastal protection worksSeawalls or revetments are commonly usedto protect property from coastal erosion andare often constructed in response to a short-term storm erosion event. The effect of suchhard structures in a dynamic beach system isto locally accelerate sediment transportprocesses, often leading to reduced beachlevels and erosion on adjacent beaches.Thus the original erosion ‘problem’ is solvedbut the beach itself may lose its value as acoastal protection or recreational asset.

In cases of continuing coastline recession, aseawall does not halt the underlying erosionprocesses and can sometimes exacerbate thesituation. In these cases, the beach levels infront of the wall are steadily lowered, eventuallyleading to stability problems for the wall itself.

Properly engineered seawalls are an effectivemeans of protecting property from extremeevents, but they are relatively expensive andrequire continuing maintenance costs. Oftenlandowners have little option but to protecttheir property from persistent erosion. Inthese cases, it is generally preferable thatwalls are constructed on, or landward of, theproperty boundary and along an alignment

consistent with structures on adjacentproperties. Ideally, this alignment shouldclosely approximate the natural (eroded)coastline position.

Rock walls built in response to a severe short-term erosion event are often of a substandarddesign and incorporate inadequately sizedarmour units. These walls typically requiresignificant continuing maintenance and maybe subject to a high risk of failure during thenext extreme event. In the worst case, suchwalls can contribute to a false sense ofsecurity when property owners continue toplace high-value structures at significant riskof severe damage or complete loss.

Control structures such as groynes andoffshore breakwaters can be used to influencethe behaviour of a particular section of beach.When properly designed and constructed,these structures are usually successful inwidening a beach and thus improvingrecreational amenity and coastal protection.The accretion of sand caused by these controlstructures is normally associated with anaccompanying erosion of an adjacent area.The downdrift erosion behind a groyne is awell-known example of this problem. Controlstructures are often used in conjunction withbeach nourishment works to minimisecontinuing maintenance requirements.

Where nearshore tidal channels occur closeto the coastline, the stability of the upperbeach can be affected. This is most likely tobe in the vicinity of a tidal inlet. Often thepatterns of tidal flows fluctuate in velocity andlocation, and can lead to recession of theadjacent shoreline. The artificial diversion oftidal flows through configuration dredgingcan be used to reduce the impacts of thistype of behaviour. The costs and the relativesuccess of these types of works are highlyvariable and are strongly dependent on thedesigner’s understanding of the key coastalprocesses.


Town Beach seawall

IntroductionDetails of studies of coastal processes for the Mackay region are presented in previouschapters. The objective of quantifying these coastal processes is to provide anunderstanding of the behaviour of thecoastal systems and to develop appropriatecoastal management strategies. The purposeof this chapter is to present the main findingsof the study in relation to individual beacheswith reference to the coastal managementissues discussed in the previous chapter.

Bakers Creek to ShellgritCreekThe coastal section between Bakers Creek andShellgrit Creek has only limited developmentinfrastructure and comprises mainly reserves(figure 56 summarises the land tenure). TheMackay City Strategic Plan shows a designationof open space and recreation.

The coastal section is formed entirely fromHolocene depositional processes. A system ofdunes of low to medium height has developedat the shoreline, backed by a relatively low-lying backshore area. This area is drained by a series of small shore-parallel creeks,including Shellgrit Creek, which flows outacross the intertidal flats at a pointapproximately midway between BakersCreek and the Pioneer River.

Erosion prone area widthsThe calculation of erosion prone areas has beenreviewed following techniques establishedby the former Beach Protection Authority(refer to Coastal Management chapter). Thebreakdown of erosion prone area widthcomponents is given in table 34). Based onthese values, the existing erosion prone areawidth of 80m is considered to be appropriateand is unchanged (figure 56 shows thewidths of erosion prone areas for thiscoastal section).

Effects of sea-level riseThe response of the system of tidal flats inSandringham Bay and south of the PioneerRiver to sea-level rise is difficult to evaluate.Detailed modelling of long-term morphologicalchanges is complex and is beyond the scopeof the present study; however, estimates canbe made of the likely response of the upperbeaches.

The system response to an expected sea-level rise associated with the greenhouseeffect of 0.3m over the next 50 yearsincludes:

� the Bakers, Sandy and Alligator Creekestuaries acting as a sediment sink – i.e.there will be a net accumulation of marinesediments;

� an increase in the level of the intertidalflats; and

� a reduction in the width of the intertidalflats in Sandringham Bay.

In general, a delta formation that hasreached an equilibrium configuration willtend to reduce in area in response to a sea-level rise as the estuary draws sediment fromthe coastal system. This is expected to occurin Sandringham Bay. The Bakers, Sandy andAlligator Creek systems are not thought to beexporting beach material-size sediments tothe coast and would act as sediment sinks.The seaward edge of the tidal flats is likelyto recede as elevated water levels movesediments onshore where they are trapped in the estuary and delta system. The tidalflats would tend to maintain a minimum planarea as the recession would be limited by thesheltering effect of the Dudgeon Point andHay Point headlands.

As depicted in figure 38, the tidal flats northof the Bakers Creek entrance arecharacterised by onshore wave-drivensediment transport, which is approximatelybalanced by the net longshore transportclose to the shoreline. This onshoresediment transport would be expected tocontinue following a sea-level rise, althougha significant proportion of sediment will beretained on the tidal flats as the bed levelincreases proportionally to sea-level rise. Thenet rate of sand reaching the upper beachsystem would therefore be reduced, and asthe net longshore transport would remainunchanged the upper beach would erode inresponse.

Assuming that the nearshore sea bed levelincreases at the same rate as the rise inmean sea-level, the rate of accumulation onthe tidal flats per metre length of coastline is(a/N x B) m3/m/a (where a/N is the rate ofsea-level rise). For an indicative width (B) of2.5km, this rate is therefore in the order of15m3/m/a, which is significantly higher than theestimated present rate of onshore sedimenttransport. It is likely that some erosion overparts of the profile will occur and that theedge of the tidal flats will recede.

Sea-level rise will cause some profileredistribution to occur as described by theBruun Rule. However, it is unrealistic toassume that sand from the upper beach willbe distributed across the entire profile, whichis of the order of 2 to 3km wide. It is predictedthat this will be limited to the upper part ofthe profile and SBEACH model simulationsshow that during a storm event with a waterlevel corresponding to MHWS the width ofthe active profile is in the order of 100 to150m. For the purposes of estimating a valuefor G, shoreline recession associated withsea-level rise, a depth of closure of 0m AHDhas been adopted. The Bruun Rule has beenapplied to this coastal section using thismodified depth of closure (table 33).

Based on the assumption of equilibriumnearshore beach profiles, an anticipatedshoreline recession of 5m associated withsea-level rise associated with the greenhouseeffect along the coastal section betweenBakers Creek and Shellgrit Creek has beenestimated over the next 50 years.

individual beaches17 Management of


Table 34 Erosion prone area width calculations,Bakers Creek to Shellgrit Creek

Parameter Value (m)

Long term erosion component (N x R) 20(based on historical fluctuations)

Short term erosion component (C) (estimated) 30

Recession related to the sea level rise associated 5with the Greenhouse effect (G) 5

Dune scarp component (D) 5

Calculated width 80

Existing width 80

Town Beach and Far BeachThe coastal section between Shellgrit Creekand the Pioneer River is adjacent to theMackay city centre and has extensive areasof residential and tourism development(figures 56 and 57 provide a summary ofland tenure). The area is also important tothe local community for recreation, and anumber of parks and reserves provide verygood public beach access.

East Mackay and South Mackay arecharacterised as relatively low-lying landfronted by a system of narrow dunes. Manyof the residential areas have been artificiallyreclaimed and filled as part of a progressiveexpansion of urban land use for mainlyresidential purposes. Much of the EastMackay landform is relatively recent ingeological terms, and once formed part ofthe Pioneer River outer estuary.

Erosion prone area widthsA review of the erosion prone area widthshas been undertaken in accordance with theformer Beach Protection Authority’srecommended procedure (figures 56 and 57summarise the recommended revisions).

The erosion prone area width at the southernend of Far Beach in the vicinity of ShellgritCreek has been increased from 80 to 400m.This is recommended to allow for the increasedpotential for long-term recession associatedwith the fluctuations in the creek entrance.

Far Beach is currently undergoing acontinuing trend of erosion due to thechanges in the Pioneer River entrance. Theprimary deposition zone of sedimentstransported from the Pioneer River prior to1898 was approximately midway along theFar Beach section. The present configurationof the river training wall, establishedapproximately 100 years ago, has shifted theprimary zone of deposition to the area south-east of the entrance in the lee of Flat TopIsland. This has resulted in a reduction ofonshore sediment transport to Far Beach.

The components of the erosion prone areawidth in the section between Shellgrit Creekand Illawong Park (including the rock wall)are detailed in table 35. Using these valuesthe recommended erosion prone area widthis 135m, increased from the existing value of 80m.

The erosion prone area width between thenorthern end of Illawong Park and the TownBeach rock wall is calculated in table 36. Usingthese values, the recommended erosionprone area width is 90m, an increase fromthe existing value of 80m.

Sea-level rise associated with thegreenhouse effect is expected to increase the rate of shoreline recession over the nextfew decades. At the northern end of TownBeach the present rate of accumulation isestimated to be 5000m3/a, which is equivalentto a uniform increase in bed levels of 8mm/a.This rate would approximately balance therequirements of sea-level rise, resulting in anegligible net effect and the presentaccretion trend will be halted.

The calculation for the Town Beach section,given in table 37, for the erosion prone areawidth therefore contains nil recession

associated with Greenhouse sea-level risedue to its offset against the anticipatedaccretion occurring in the area. Using thesevalues, a reduction to 60m from the existingerosion prone area width of 80m is determined.

Illawong Park rock wallA rock wall has been constructed seaward ofthe Illawong Park recreation reserve to counterthe erosion trend at Far Beach. Associatedwith the rock wall are reduced beach levelsand recession of the adjacent beaches due to terminal effects. The wall is also prone todamage during severe storm events.

The continued maintenance or upgrading of theIllawong Park rock wall is not recommended.Ideally, the wall should be removed andexisting structures in the park be relocatedlandward to allow the beach to fluctuatenaturally.

Alternatively, some beach nourishment orscraping works could be undertaken to improvethe upper beach and the general amenity ofthe area. Periodic placement of sand in frontof the wall would also improve its ability towithstand storm wave attack and reducemaintenance requirements.


Table 36 Erosion prone area width calculations,Illawong Park to Town Beach rock wall

Parameter Value (m)

Long term erosion component (N x R) (nominal) 10


Recession related to the sea-level rise associated 21with the Greenhouse effect (G)


Calculated width 90

Existing width 80

Rock wall at Far Beach.

Table 37 Erosion prone area width calculations,Town Beach

Parameter Value (m)





Calculated width 60

Existing width 80

Table 35 Erosion prone area width calculations,Shellgrit Creek to Illawong Park

Parameter Value (m)

Long term erosion component (N x R) 50(based on current recession rate)




Calculated width 135

Existing width 80

Town Beach coastlineSurvey and aerial photography data indicatea low rate of accretion at the northern end ofTown Beach. Sediments deposits in thevicinity of the training walls are largely due tothe effects of the walls and could be used asa source of beach nourishment sand. Thesuitability of this material would depend on thesilt content and its use would be subject toan examination of associated environmentalimpacts. Due to the low rates of accretion,continuing sand extraction is consideredinappropriate.

The development of residential areas in EastMackay has included reclamation works andalterations to the natural drainage system,including:

� the excavation of a large area on the tidalflats adjacent to the reclamation onBinnington Esplanade;

� the subsequent construction of a rock wallto protect the road;

� the diversion of stormwater flowssouthward to Shellgrit Creek; and

� the associated closure of the small tidalcreek entrance, locally known as PotholeCreek, at the southern end of Town Beach.

The closure of Pothole Creek has resulted inlocalised changes to the nearshorebathymetry at the southern end of Town Beach.The volume of sand previously associatedwith the ebb tide delta is slowly migratingonshore and northward towards the rock walland extraction site off Town Beach. This isexpected eventually to help form a sandybeach at the base of the wall and thusimprove the general amenity of the area.

It is recommended that beach nourishmentor scraping be undertaken to fill the dredgedhole and build up the upper beach in thevicinity of the Binnington Esplanadeshorefront. Ideally, the nourishment shouldcompletely cover the rock wall, reducing itsdetrimental effects while retaining its coastalprotection attributes. These works wouldalso improve the structural integrity of thewall itself.

Potential sources of sand include:

� the sandbank immediately to the south of the rock wall;

� the area of natural reclamation to the northof the site adjacent to the training walls(depending on suitability); or

� the outer section of the ebb tide delta of the Pioneer River entrance.

Storm tide hazardThe narrow dune system and the relativelylow-lying backshore area make the Far Beachand Town Beach section vulnerable to stormtide inundation. This is exacerbated by thecontinuing trend of erosion. The impacts of the1918 storm tide event was focused primarilyon the East Mackay area and it is likely that asimilar event would pose a severe hazardthrough East Mackay and South Mackay. It isrecommended that the dune system alongFar Beach and Town Beach is carefullymanaged and enhanced where possible, toprovide a protective buffer against potentialstorm tide inundation.

The existing development (Illawong BeachResort) adjacent to the Shellgrit Creekentrance is located in the erosion prone areaand is vulnerable to storm tide inundation. It is recommended that the density ofdevelopment should not be increased in this area.

Pioneer River entranceThe observed behaviour of the Pioneer Riverentrance is closely linked to the continuingoutput of sediments from the estuary and theeffects of the training wall structures on thepatterns of sedimentation.

Despite the high rates of commercialextraction of sand and gravel from the tidalreaches of the Pioneer River, the subtidaldelta at the entrance is continuing to accreteat an estimated rate of 45,000m3/a. Theeffects of the extraction operations and theinfluence of sea-level rise associated withclimate change are expected to result in agradual reduction of this growth rate.

The deeper sections of the delta betweenFlat Top Island and East Point are a potential

site for commercial sand extraction, but itseconomic feasibility would need to beexamined.

The training walls at the entrance to thePioneer River, constructed over the period1890 to 1905, have markedly altered thesediment transport processes. Before 1898,a long continuous sand spit extended fromthe present location of East Point towards thesouth-south-west. Sections of this spit wouldepisodically break away in response tofloods and storm events, and a proportion ofthe sediments would migrate onshore tofeed Far Beach.

In its present configuration, the entrance hasthe appearance of a subtidal delta extendingtowards the south-east into the lee of FlatTop Island. It is anticipated that the delta willform a partial tombolo with Flat Top Islandover the next 50 years. This has potentialimplications for upstream flood levels in thePioneer River.

The training works in the river entrance haveeffectively stabilised the configuration of theouter bar area. Although a worsening ispredicted, the hydraulic efficiency of theentrance in its present configuration is betterthan the pre-1898 case. There is, therefore,no recommendation to alter the entrancetraining walls.

To improve estimates of the accretion ratesand understanding of the behaviour of thePioneer River entrance, an enhanced programof monitoring should be implemented. Thiswould be in the form of detailed soundingsover the area encompassing East Point, FlatTop Island and Town Beach. The use of newlydeveloped remote sensing techniques couldminimise costs. The capture of regular verticalaerial photography should continue andextend to a point seaward of Flat Top Island.


Extensive sand deposits occur at the mouth of the Pioneer River.

Harbour Beach andLamberts BeachHarbour Beach and Lamberts Beach form acontiguous coastal section from the PioneerRiver entrance at East Point to Slade Point. Thesection is characteristic of an open coast beach,relatively exposed to the prevailing wave climateand the nearshore tidal currents. Before theconstruction of the harbour in 1935 to 1939, thebeach alignment had formed in approximateequilibrium with the regular throughput ofnorthward longshore sediment transportfrom the river entrance and the location ofthe bedrock headland of Slade Point.

The net longshore sediment transport rate atHarbour Beach is estimated to be 35,000m3/a.This relatively high sediment supply combinedwith prevailing onshore winds has resulted inthe formation of extensive dune fields morethan 20m in height towards the northern endof the beach.

Until recently, the primary use of the HarbourBeach section was associated with the port.Large areas of the dunes in the central sectionof Harbour Beach have been cleared andlevelled for port facilities and other industrialuses. North of the harbour, the extensivedune fields and backshore areas have beenset aside as conservation reserves (figures57 and 58 detail land tenure). High-densityresidential and tourism infrastructure has beenestablished in the area south of the harbour.This has included an extension to the harbourbasin for a small boat marina and theredevelopment of the community recreationfacilities and the surf club. The remainder ofthe area is undeveloped at present howeverfurther residential and tourism development isproposed. Immediately behind the southernsection is a system of tidal wetlands includingBassett Basin, a fish habitat area declaredunder the Fisheries Act 1994.

The formerly continuous coastal sectionbetween the Pioneer River entrance andSlade Point is now interrupted by the harbourwalls. Small fillets of accretion can be seenimmediately north and south of the walls anda marked trend of erosion has been observedalong the northern section and LambertsBeach. Only a very minor quantity is bypassingthe harbour naturally.

The extent of the accretion on the southernside of the harbour is controlled by the volumeof sand commercially extracted from the area,recently averaging about 45,000m3/a.Interception of this sand is important to theoperation of the port as it controls the potentialsedimentation of the harbour entrancechannel. The extraction is generally managedto minimise recession of the shoreline.

The coastline model of Harbour Beach alsoprovides an estimate of the downdrift effects

of longshore transport past Slade Point. As the centre of Harbour Beach north recedesand takes up more of a pocket beachalignment, the net northward longshoresediment transport rate will reduce. This hasimportant implications for the stability ofbeaches further north, including BlacksBeach. The results indicate that the rate ofsediment transport bypassing Slade Pointwill reduce by 3,000m3/a over a 50 yearsimulation period.

Erosion prone area widthsA review of the erosion prone area widthshas been undertaken (figures 57 and 58summarise recommended revisions).

The components of the erosion prone areawidth in the section in the vicinity of EastPoint are contained in table 38. Note that theonshore transport of sediment in thenearshore area adjacent to the Pioneer Riverentrance will effectively offset any recessiondue to the sea-level rise associated with theGreenhouse effect.

Accordingly, using these values therecommended erosion prone area width is 75m,reduced from the previous value of 110m.

Between East Point and a point 800m southof the small craft harbour, the recommendederosion prone area width is 75m, reducedfrom the previous value of 110m. This isshown in table 39.

In the section immediately south of theharbour breakwater, the recommendederosion prone area width transitions from 75to 30m. This calculation assumes a linearreduction of the values of both the long–termerosion (N x R) and the sea-level rise

associated with the Greenhouse effect (G)components to zero at the breakwater. This isbased on the observed trend of accretion inthis area and assumes:

� the ongoing supply of sediments from thePioneer River entrance is not interrupted; and

� the management of the extraction activitiesminimises the potential for recession ofthe shoreline from the present position.

Immediately north of the harbour breakwaters,the recommended erosion prone area widthis 45m, reduced from the previous value of110m (table 40). This value transitions to theHarbour Beach north erosion prone areawidth of 160m over a distance of 1000m.

The components of the erosion prone areawidths over the remainder of Harbour Beachnorth are detailed in table 41. Using thesevalues the recommended erosion prone areawidth is 160m, increased from the previousvalue of 110m.

The recommended erosion prone area widthof Lamberts Beach is 110m, identical to theexisting value (table 42).


Table 39 Erosion prone area width calculations,East Point to 800m south of the small craft harbour

Parameter Value (m)



Recession related to the sea-level rise associated 20 with the Greenhouse effect (G)


Calculated width 75

Existing width 110

Table 42 Erosion prone area width calculations,Lamberts Beach

Parameter Value (m)

Long term erosion component (N x R) 35(derived from coastline model)





Existing width 110

Table 38 Erosion prone area width calculations,East Point

Parameter Value (m)

Long term erosion component (N x R) 20




Calculated width 75

Existing width 110

Table 40 Erosion prone area width calculations,immediately north of the Mackay Harbourbreakwater

Parameter Value (m)

Long term erosion component (N x R) 0




Calculated width 35

Existing width 110

Table 41 Erosion prone area width calculations,Harbour Beach north

Parameter Value (m)

Long term erosion component (N x R) 80(derived from coastline model)





Existing width 110

Slade PointSlade Point is a popular residential area witha significant number of properties locatedclose to the coastline on both the eastern sideof the headland and the western shoreline,as shown in figure 59. In the south westerncorner of Slade Bay, the topography shows areduction in height towards the entrance toMcCreadys Creek.

Slade Point BeachSlade Point Beach is a small section ofpocket beach perched on the rocky platformat the base of the eastern side of the headland.The high potential longshore sedimenttransport rate relative to the actual supplyprecludes the regular formation of a sandybeach, although this sometimes occurs underfavourable conditions. The beach generallycomprises rocky material in the form of graveland cobble mixed with some sand.

Before the establishment of residentialsubdivisions on Slade Point, it is likely thatan overland aeolian transport of sand existedbehind the headland from Lamberts Beach toSlade Point Beach. This sand was probablyalso a source of supply to Slade Point Beachwhich has now been eliminated. The effecton Slade Point Beach is exacerbated by thegeneral erosion trend along Harbour Beachnorth and Lamberts Beach caused by theblocking effect of the harbour walls.

The calculation of erosion prone area width forSlade Point Beach indicates a value of 100m(table 43). Given that the beach contains arelatively high proportion of cobbles androcks, the existing value of 95m is consideredacceptable and is unchanged.

Western coastline of Slade PointThe inshore section along the westernshoreline of Slade Point comprises a rockyplatform overlain with sand and mud. Thefluctuations in the alignment of McCreadysCreek and the variability in sand supply fromaround Slade Point cause shoreline movementsalong this section. The volume of sand on theupper beach is dependent on the effects ofhigh-energy wave events, which generatebursts of high short-term longshore transport.These result in episodic sequences of erosionand accretion followed by extended periodsof little change. Due to the relative shelteringand the effects of McCreadys Creek, theshoreline variability is more noticeable at thewestern end of the beach.

A number of private landholders haveconstructed low rock walls to protect theirproperties against episodic erosion. Due tothe reflective nature of these structures,sandy upper beaches are rarely establishedalong their lengths. Where possible, furtherconstruction of these walls should be avoided,although it is recognised that continuingprotection of public and private infrastructureis necessary. Rock walls should be constructedonly on private property.

In some cases, the rock walls are critical for theprotection of houses and other infrastructure.A review of the adequacy of these existingwalls to withstand storm wave attack, alongwith the potential for overtopping during asevere storm should be undertaken toensure the property owners are aware of thepotential risk of failure and/or flooding.

Overall trends in the available hydrographicsurvey data indicate that the volume of thetidal flats in this area is relatively stable andit appears that the embayment has reachedan approximate equilibrium in geologicalterms. There is no clear evidence of a recenterosion trend.

The erosion prone area width for the sectionbetween Slade Point and McCready’s Creekis 55m and remains unchanged (table 44).


Table 43 Erosion prone area width calculations,Slade Point Beach

Parameter Value (m)






Existing width 95

Table 44 Erosion prone area width calculations,Slade Point to McCready’s Creek

Parameter Value (m)





Calculated width 55

Existing width 55

Slade Point and Slade Bay in the background.

Blacks BeachThe northern section of Blacks Beach hasbecome a relatively high growth area ofMackay City, with increasing areas of residentialand tourism development. A number ofnew residential subdivisions have beenestablished or are planned in the area, alongwith associated commercial developmentssuch as hotels, restaurants and shoppingprecincts. The southern end of the beachcomprises an extensive area of publicreserve (figure 59 shows land tenure).

Erosion prone area widthsThe components of the erosion prone areawidth for the southern section of Blacks Beachbetween McCready’s Creek and a pointopposite Anglers Parade is contained in table45. Using these values the recommendederosion prone area width is 80m and remainsunchanged.

Widths of erosion prone areas have beenassessed, taking into account the sedimenttransport processes and the likely influence ofsea-level rise associated with the Greenhouseeffect (figure 59). Since the continuingmaintenance of the rock walls at the northernend of Blacks Beach is the responsibility ofprivate landholders and cannot necessarilybe guaranteed, the assessment doesn’t takeinto account the present efforts to hold the line.Therefore erosion prone area widths do nottake into account the effects of the rock walls.

The erosion prone area width for the northernsection of Blacks Beach is calculated in table46. The calculation includes an adopted value of 40m for the long term erosion component(N x R), based on the analysis of previouscoastline changes.

Using these values the recommended erosionprone area width is 150m, an increase fromthe existing values which vary between 80and 140m.

Effects of sea-level riseThe primary sediment transport path fromSlade Point to Slade Bay is across theintertidal flats. The rise in seabed level in thedeposition zone behind Slade Point will besupplied by the incoming sediment transportrather than by recession of the upper beach. Theimplication, however, is that the net downdriftsupply to the centre of Blacks Beach will bereduced, and since the outgoing potentiallongshore transport rate at the northern endof Blacks Beach remains unchanged, therewill be a generalised trend of recession.

The plan area of the Slade Bay tidal flats isapproximately 200ha. The plan area geometryis controlled by the presence of the headlandand the direction of the prevailing waveclimate and is expected to remain relativelyconstant following a sea-level rise. Assumingthe seabed rises in direct response to a 0.3msea-level rise over 50 years, the rate ofaccumulation and therefore the net loss ofsediment to the downdrift system would be inthe order of 12,000m3/a. This effect is likelyto be seen between the centre and the northernend of Blacks Beach in the vicinity of thecoastline bulge, which will recede in responseto the reduced sediment throughput rate.

This is superimposed on the recessioncaused by profile readjustment asdetermined by the Bruun Rule.

In the absence of the rock walls at BlacksBeach, the net loss of sand would be madeup from a continuing erosion of the dunesand the coastline would recede until thealignment accommodated the lower sedimenttransport rate. Over a coastline length of 2km,the average rate of recession is 6m3/m/a.Using the schematised beach profile forBlacks Beach given in figure 54, this convertsto a recession rate of 21m over 50 years.

Rock walls Continued maintenance of the Blacks Beachrock walls would protect the present coastalalignment, although considerable erosionwould be expected to occur on the beachesadjacent to, and seaward of the walls.Additional works would be required tostrengthen the toes of the walls and theirflanks as the adjacent coastline recedes.Some enhancement to the structural qualityof the walls, possibly including increasedcrest levels, may be necessary due to anincreased exposure to storm wave attackcaused by lowered beach levels.

During a storm, the majority of waves breakseaward of the upper beach. The depth ofwater at the base of the wall thereforegenerally limits the largest waves impactingon the rock walls. This, in turn, is controlledby the absolute water level and the beachlevels. A review of the capacity of the existingwalls to withstand severe waves, along withthe potential for overtopping during an eventwith a 100 year return interval, should beundertaken and should include aconsideration of anticipated conditions.

Due to the potential for continuing shorelinerecession, it is preferred that new developmentshould not be established within the erosionprone area. The location of high-density landuses such as holiday apartments should becarefully considered. Significantimprovements to existing residential andcommercial infrastructure should also beavoided and where possible, the relocationof buildings to the landward side of affectedproperties should be encouraged. The rockwalls have an adverse effect on the beachsystem and are not a good long-termsolution to any present or future problems.Significant investment in the upgrading ofthe rock walls in their present positionshould be avoided. Instead, funding shouldbe directed towards a planned retreat andthe eventual removal of the rock walls.

Alternative management optionsThe overall objective of a managementstrategy is to limit the impacts of the rockwalls on the beach system and ensureprotection of private properties. Establishinga sandy beach seaward of the rock walls willimprove the recreational amenity of the areaand in enhancing the effectiveness of therock wall structures. Alternative options thatmay be considered include:

� complete or partial acquisition of affectedproperties including site rehabilitation andremoval or relocation of rock walls. Costsare likely to exceed $10 million. However,the program could be staged over a numberof decades and could include methods ofreducing overall costs such as short-termlease-back; or100 Mackay Coast Study

Table 45 Erosion prone area width calculations,Blacks Beach (south)

Parameter Value (m)

Long term erosion component (N x R) 20(based on historical fluctuations)




Calculated width 80

Existing width 80

Table 46 Erosion prone area width calculations,Blacks Beach (north)

Parameter Value (m)

Long term erosion component (N x R) 40(derived from historical coastlines)


Recession related to the sea-level rise associated 21with the Greenhouse effect (G) due to the reduction in sediment supply resulting from the accretion of the tidal flats in Slade Bay

Recession associated with profile re-adjustment 21related to the sea-level rise associated with the Greenhouse effect (G)



Existing width 80

� the establishment of a control structure inthe vicinity of the affected section, alongwith a limited program of beach nourishment.The structure, possibly in the form of anoffshore breakwater, would create a salient,modifying the beach’s plan shape andhence reducing the anticipated trend ofshoreline recession. The high tide rangeand the potential effects of severe stormevents would complicate the design of thestructure. A program of beach nourishmentwould also be required to mitigate theexpected erosion effects downdrift. Overallproject costs could be as high as $2 million.

Dolphin Heads and EimeoThe Dolphin Heads and Eimeo area is usedextensively for residential purposes, alongwith some tourist development and areas ofopen space (figure 60 shows land tenure). A number of freehold properties have beenestablished close to the shoreline.

Erosion prone area widthsA review of erosion prone area widths in thevicinity of Dolphin Heads was undertaken forthe Authority in 1987 taking into account thelocal coastal processes. A further review ofthis work has been undertaken including theeffects of Greenhouse sea-level rise.

The components of the erosion prone areawidth for Eimeo Beach are shown in table 47.Using these values, the recommendederosion prone area width is 80m, an increasefrom the existing value of 55m (figures 59and 60 show the recommended values).

Management issuesA series of low rock walls have beenconstructed to halt erosion along theseaward boundaries of these properties,particularly the beaches on the lee side ofDolphin Heads and Eimeo headland. Severalallotments at the end of Eimeo Beach haverock walls on their seaward boundary forprotection against damage from storm waves.

Several short rock groynes have beenconstructed on the rocky intertidal platformin an attempt to encourage the build-up of

sandy material near the shoreline at DolphinHeads. It is unlikely that the groynes willhave any long-term effect on improving thebeaches and attempts to upgrade thegroynes are not recommended.

A number of private properties along theDolphin Heads to Eimeo section close to theshoreline are vulnerable to storm tideinundation and/or damage from severe waveconditions. The anticipated sea-level riseassociated with the greenhouse effect isexpected to exacerbate the situation,particularly along the eastern end of EimeoBeach, where the alignment is controlled bythe level of the bedrock platform. A review ofthe adequacy of the existing protective rockwalls along this section should beundertaken to guarantee structural integrityand sufficient crest levels to protect against astorm event with a 100-year return interval.

At the eastern end of Eimeo Beach a numberof freehold properties are located within theerosion prone area near the end of the sandspit close to the tidal creek entrance. Due tothe close proximity of private dwellings to theshoreline and the resulting vulnerability toerosion and storm tide flooding hazards, it isrecommended that:

� increased development density should notbe allowed; and

� a program of acquisition of these propertiesshould be undertaken where possible toreduce development rights or convert theprivate freehold land to an open spacedesignation (this would provide addedbenefits for public beach access).

Bucasia BeachBucasia Beach has formed between theheadlands of Eimeo and Shoal Point as acontinuous sandy beach. The beach is partof the northerly throughput of sedimentsderived primarily from the Pioneer River.

Erosion prone area widthsIt is recommended that the maximum erosionprone area width of 400m in the vicinity of theentrance to Eimeo creek should be unchanged.A linear transition from zero to 400m isproposed for the erosion prone area widthbetween Eimeo headland and Eimeo Creek.

Analysis of survey data and the assessmentof longshore sediment transport fluxesindicate a continuing trend of accretion alongBucasia Beach. The erosion prone area widthcalculations for the southern section ofBucasia Beach is contained in table 48.Using these values the calculated erosionprone area width is 70m, and the existingvalue of 80m is considered acceptable.

Trapping of sediments on the tidal flats andassociated downdrift erosion, similar to thatseen at Slade Bay, would occur in Sunset Baydue to sea-level rise. In this case, theaffected section of tidal flats is approximately160,000m2 in plan area; therefore thedowndrift loss is in the order of 1000m3/a.Over the 3km coastline length of BucasiaBeach, the associated recession would benegligible.

The erosion prone area width for the northernsection of Bucasia Beach is shown in table49. Using these values the recommendederosion prone area width is 70m, reducedfrom the existing value of 110m. Proposedrevisions to erosion prone area widths aresummarised in figure 60.

Management issuesClose to the Eimeo Creek entrance, a caravanpark has been established near the shoreline.Aside from this, the Bucasia Beach shore frontis free from development. Although extensiveresidential development has extendedthrough to Shoal Point, a wide buffer zoneexists between freehold property and thecoast (figure 60). This feature, along with theoverall trend of accretion, should result inminimal coastal management concerns. It isrecommended that the development-freebuffer be maintained in its present form.

The caravan park is at risk of inundation fromstorm tide due to its proximity to the creekentrance. It is recommended that no increasein the density of development be permittedin this area.


Table 47 Erosion prone area width calculations,Eimeo Beach

Parameter Value (m)





Calculated width 80

Existing width 55

Table 48 Erosion prone area width calculations,Bucasia Beach (south)

Parameter Value (m)





Calculated width 70

Existing width 80

Table 49 Erosion prone area width calculations,Bucasia Beach (north)

Parameter Value (m)





Calculated width 70

Existing width 110

IntroductionA detailed review of coastal processes in theMackay region has been undertaken in orderto quantify the behaviour of coastal systemsand predict future trends. This review hasbeen used to formulate recommendationsfor future coastal management. Specificrecommendations for individual beachesare detailed in the previous chapter.

Commercial sand extractionIt is likely that applications for sand extractionpermits in the coastal areas of the Mackayregion will continue in the future. Fill forcoastal development, raw materials for theconstruction industry and possibly sand forbeach replenishment are likely to be requiredon a continuing basis.

The review by GHD (1998) of the commercialopportunities for sand extraction in thePioneer River system included the followingrecommendations:

1. Permitted extraction from sites in thelower reaches of the Pioneer River shouldbe reduced from approximately100,000m3/a to 22,000m3/a.

2. The existing extraction from sites betweenEast Point and the southern breakwater ofthe harbour could continue at a rate of upto 42,000m3/a.

3. Future alternative extraction operationsshould consider the reserves of sand andgravel trapped by the water resourcestructures at Dumbleton, Mirani and Marian.

A further review of the fluvial processes ofthe Pioneer River has not been undertakenas part of this study. It is apparent from theevidence provided by GHD that the sand andgravel extraction activities are contributing toa net reduction of sediments in the tidalreaches of the river. A reduction of the permittedextraction quantities in the river as proposedby GHD would therefore be prudent.

The analysis of coastal processes undertakenfor this study indicates that the net fluvialsupply of beach material sized sediments tothe coastal system from the Pioneer River isin the order of 85,000m3/a. Approximately35,000m3/a is transported northward alongHarbour Beach, where it is trapped by thesouthern breakwater of the harbour.

About 45,000m3/a accumulates on thePioneer River entrance bar and a smallamount, in the order of 5,000m3/a, istransported westward from the river entrancetowards Town Beach.

Despite the apparent over-extraction of sandfrom the lower reaches, the fluvial supplyfrom the Pioneer River is expected to continueat the present rate in the medium term. Somereduction may be expected due to the effectsof sea-level rise associated with thegreenhouse effect.

The commercial extraction of sand from thesouthern section of Harbour Beach hasprovided benefits in supplying valuablematerials to the local economy. The operationsalso reduce potential problems associatedwith windblown sand in the small craft harbourand port area and reduce likely hazards tonavigation caused by possible siltation in theharbour entrance.

GHD (1998) considered that the beachesnorth of the harbour have probably adjustedto the net loss of sand removed by thecommercial extraction activities. The presentstudy has shown that this is not the case.The extraction of sand south of the harbouris interrupting the natural coastal processesby removing considerable quantities of sandfrom the active littoral system and is notsustainable over the long term.

The present study has also shown thevulnerability of many of the Mackay beachesto erosion including the impacts of theanticipated sea-level rise associated with thegreenhouse effect. In general, the removal ofsand from the tidal flats through commercialextraction activities is not recommended.Site-specific issues are as follows:

� the northern end of Town Beach is accretingat a low rate, partially due to the influenceof the Pioneer River entrance trainingwalls, and is not a suitable source forcontinuing extraction;

� the tidal flats seaward of Town Beach andFar Beach are not suitable as extractionsites as the rates of sediment transport(and therefore infill) are very low. This canbe clearly seen in sequences of aerialphotographs over previous extractionareas seaward of Town Beach; and

� the estuary of Bakers Creek appears to be

a net sediment sink for marine sedimentsunder present and future sea-levelconditions. Extraction of sand from withinthe estuary and the adjacent tidal flatswould reduce the quantity of availablesediments from the active system and istherefore not sustainable.

The accumulation of sediments near thePioneer River entrance at an estimated rateof 45,000m3/a does provide a potentialsource for commercial sand extraction. Theebb tide delta of the river has been accretingseaward into the lee of Flat Top Island sincethe changes to the entrance training wallsmade in the late 19th century. Extraction ofthe recently deposited material near the edgeof the delta would not significantly affectprocesses on the adjacent coastline.

Based on present trends, it is anticipatedthat the delta will continue to accrete into thesheltered area in the lee Flat Top Island. Overtime, this may have an effect on the hydraulicefficiency of the river entrance and potentiallyincrease the risk of flooding in the city.Maintaining the efficiency of the channelthrough the bar delta by dredging wouldtherefore avert a worsening of potential floodlevels in the Pioneer River.

Commercial extraction of sand from the deepersections of the Pioneer River entrance deltawould probably require the use of specialisedplant, such as trailer suction hopper dredges.The establishment and operational costs ofthis type of plant are clearly higher than thecosts of land-based equipment used presently.A cost-effective approach may be to extractsand in large, less-frequent campaigns andstockpile the material at a suitable locationonshore. Any proposal for large scaleextraction should be subjected to a detailedassessment of potential impacts.

recommendations18 Conclusions and


Effects of the harbour wallsThe Mackay Outer Harbour was constructedduring 1935 to1939. Its design and locationare generally regarded as being successful inproviding all-tide access to the port for themajority of commercial shipping.

The harbour walls extend some 1,200moffshore from Harbour Beach and have aconsiderable effect on waves and tidal flowsin the adjacent areas. Numerical modellinghas shown that tidal current velocities haveincreased by up to 30 percent at a locationimmediately seaward of the harbourcompared to pre-1935 conditions. Theintrusion of the walls into the tidal streamalso results in a net residual flow patterndirected towards the harbour. The numericalmodelling has shown that the recentextension works for the construction of thesmall boat harbour appear to have had anegligible additional impact on tidal flows.

The majority of the longshore sedimenttransport on Harbour Beach is blocked by thesouthern breakwater. Numerical modellingindicates that negligible longshore sedimenttransport occurs beyond a point approximately500m offshore, although a minor quantity ofsediment bypasses the harbour naturally bythe action of waves and tidal flows. The rateof natural bypassing has not been quantified,but it is likely to be small in comparison withthe net longshore sediment transport rate onHarbour Beach. Accretion of southern HarbourBeach has been limited by sand extractionactivities. Clearly, a reduction in the rate ofextraction permitted in this area will result ina trend of accretion at the southern breakwaterand eventually lead to an interruption tonavigation of the harbour entrance.

Survey data analysis and numerical modellinghave shown that the northern section ofHarbour Beach is continuing to respond tothe effects of the harbour construction. Thesection immediately adjacent to the northernbreakwater has accreted in response to thereduced wave energy and tidal flows. Thisaccretion, which can be seen in aerialphotography, has a small supply both by thenatural bypassing of the harbour andartificial placement of sand.

The shoreline at the centre of Harbour Beachnorth has eroded at a rate of approximately0.85m/a over the past 20 years in responseto the reduced sediment supply. LambertsBeach and Harbour Beach north havereduced in volume at a combined rate in theorder of 13,000m3/a. This downdrift erosionwould have been much higher had it notbeen offset by the placement of 610,000m3

of dredged material on the beach to thenorth of the harbour since 1968.

The interruption of longshore sedimenttransport along Harbour Beach by the harbourwalls is expected to continue, resulting in anoticeable erosion of the northern section ofHarbour Beach and Lamberts Beach. In theabsence of compensatory placement of sand,coastline modelling indicates that, underpresent conditions, the centre of HarbourBeach north is expected to recede byapproximately 80m over the next 50 yearsdue to the interrupted sediment supply.

The net northward sediment transportbypassing Slade Point has been affectedslightly by the altered coastline configurationof Harbour Beach north. The calculation oflongshore sediment transport indicates that therate along Harbour Beach north has reducedfrom 35,000m3/a to 33,000m3/a since harbourconstruction. In 50 years this is estimated toreduce to 30,000m3/a in response to thecontinuing coastal alignment changes.

The presence of the harbour walls and theassociated sand extraction south of theharbour are therefore directly resulting inerosion of the beach north of the harbourand will eventually cause erosion problemsto beaches further north. Options for futuremanagement are described below.

Option: Continued ExtractionAllowing the present extraction arrangementsto continue would avert problems in the Portof Mackay but would result in continuingerosion along the beaches to the north. Thecoastal systems north of Slade Point arevulnerable to loss of sediment supply, althoughthey do not appear to have been significantlyaffected to date.

Option: Cease or Reduce Rates ofExtractionConceptually, by limiting or not renewingexisting commercial sand extraction permitsthe net northward littoral transport wouldeventually be re-established along HarbourBeach. However, the complete establishmentof sediment transport past the harbourwould take a significant period of time and,due to the changed coastal alignment, thenet rate of northward sediment transport atSlade Point would probably remain reducedfor several decades.

Allowing the bypassing of the harbour bynatural littoral transport would result in asignificant maintenance problem for theMackay Port Authority. A program of regulardredging of the harbour entrance would berequired and the control of windblown sandadjacent to the southern wall could becomea problem. Due to the serious interruption tothe operation of the port, this option is notpractical and is unlikely to be considered.

Option: Artificial sand bypassingThe implementation of an artificial sandbypassing system would allow the re-establishment of sediment transport alongHarbour Beach and require no increase inmaintenance dredging in the harbour.

A range of possible bypassing systems couldbe considered. The simplest method mightbe to continue the extraction activities usingconventional trucks and earthmoving plant,and deliver the sand to an appropriate sitenorth of the harbour. Selection of anappropriate delivery site would need to takeinto account a number of environmentalimpacts including:

� the conservation significance of the SladePoint Reserve;

� the trend of accretion in the areaimmediately north of the harbour (theoutlet site would not be optimally locatedin this area);

� noise, dust and other impacts of thedelivery system;

� interruptions to the recreational value ofthe beaches; and

� potential windblown sand problemsassociated with a stockpile at the delivery site.

A preliminary recommendation for a deliverysite is Lamberts Beach. Ideally, the sandshould be placed near the centre of HarbourBeach north away from the shadow zonecreated by the harbour walls. However, thebenefit gained from a delivery site in thislocation may be negated by the adverseimpacts on Slade Point Reserve associatedwith providing access.

In summary, the most appropriate option toensure the continuity of sand supply is notadversely affected by the harbour walls isartificial sand bypassing. It is recognised thatsignificant funding and management issuesof an artificial sand bypassing system are tobe resolved prior to implementation.


Future monitoringCompetent coastal resource planning andmanagement are based on an understandingof prevailing coastal processes. Undertakingof the necessary analyses generally requiresmany years of wind, wave, current and surveydata, and the data need to be reliable andrepresentative. Without them, predictions ofshoreline change would be subject to a largedegree of uncertainty. For example, thedifference between a two-year record and a20-year wave record may mean an increasein the maximum recorded significant waveheight of more than 1m, and a substantial re-evaluation of the magnitude of extremeevents.

The cost to the community of inadequatedata can be high. Investing in data collectioncan offset both unnecessary capitalexpenditure due to over-design and costsassociated with an expensive failure resultingfrom under-design or misunderstanding ofnatural processes. Investment in datacollection reduces uncertainty and continuingexpertise is vital to ensure that the data arecorrectly collected and interpreted(Institution of Engineers, Australia 1993).

The present study has highlighted severallimitations in existing local data sets. As a result,the following recommendations are made forthe improvement of coastal process data:

� The Mackay coastline is stronglyinfluenced by the Pioneer River. Thechanges occurring to the tidal delta andthe subsequent impacts on surroundingbeaches are not easily quantified by theavailable survey data. It is thereforerecommended that a regular program ofhydrographic surveys extending over theentrance and ebb tide bar of the PioneerRiver be undertaken in conjunction withaerial photography covering the entranceand lower reaches of the River.

� As part of permit requirements, sand andgravel extraction operators are normallyrequired to engage licensed surveyors toperform pre- and post-extraction surveys.These data should be integrated into thelong-term survey record for the area.

� In the Town and Far Beach areas, the dunecrest provides an important barrier againststorm tide inundation. A long-term recordof changes to the crest height is notavailable, but is extremely important formanagement purposes.

� In general, the beach profile surveys dataare limited in the whole region, especiallynorth of Mackay Harbour. It is recommendedthat a regular survey program be developedto better quantify the coastal changes;these surveys should include land basedsurveys of the key sections of beach takenduring low tides.

� Due to the large tidal range in the studyarea, nearshore tidal currents have a largeimpact on sediment transport and,therefore, on shoreline movement. Althoughextensive current metering and hydrodynamicmodelling were undertaken for this studythese were on a regional scale and limitednearshore current data are available,especially in the Slade Bay and DolphinHeads areas. Additional collection ofcurrent data will further refine understandingof coastal processes and behaviour wherefine scale detail is important.

The development of coastal managementplans for Queensland has reinforced theneed for a comprehensive long-term datacollection program. These plans will besubject to review in the future, necessitatingcontinuing collection of wind, wave, survey andcurrent data to ensure that coastal managerscan further refine predictions of shorelinechange while allowing for responsibleplanning.


Degradation of dunes on Harbour Beach (north).

Summary ofRecommendations

Commercial sand extractionThe present study has shown thevulnerability of many of the Mackay beachesto erosion and has found that the removal ofsand from tidal flats through commercialextraction activities is not recommended, in particular:

� the northern end of Town Beach adjacentto the southern training wall of the PioneerRiver is not a suitable source forcontinuing commercial extraction;

� the tidal flats seaward of Town Beach andFar Beach are not suitable as extractionsites due to the very low rates of infill; and

� extraction of sand from the estuary ofBakers Creek and the adjacent tidal flats isnot sustainable.

The continuing accumulation of sedimentsnear the Pioneer River entrance in thesheltered area in the lee of Flat Top Islanddoes provide a potential source for commercialsand extraction. It is recognised however that extraction operations in this area wouldprobably require the use of specialisedequipment. In addition, any proposal forlarge scale extraction should be subjected toa detailed assessment of potential impacts.

Effects of the harbour wallsThe interruption of longshore sedimenttransport along Harbour Beach by the harbourwalls is resulting in a noticeable erosion ofthe northern section of Harbour Beach. Themost appropriate option to ensure that theharbour walls do not continue to adverselyaffect the northward transport of sand is toestablish a system of artificial sandbypassing.

MonitoringA number of improvements to the acquisitionof coastal process data may be made:

� a regular program of hydrographic surveysextending over the entrance and ebb tidebar of the Pioneer River be undertaken inconjunction with aerial photographycovering the entrance and lower reachesof the River.

� monitoring the crest height of dune systemsalong Town Beach and Far Beach; and

� greater frequency and spatial resolution ofbeach profile surveys including a programof upper beach surveys of key sections ofthe coast.

Rock wallsA number of rock wall structures within the Mackay Coast region may requiremanagement action, including:

� Further works to upgrade the rock wall atIllawong Park, Far Beach is not recommended.Ideally, the wall should be removed andexisting structures in the park be relocatedlandward to allow the beach to fluctuatenaturally. Alternatively, a program ofperiodic placement of sand in front of thewall could be established.

� A similar program of beach nourishment ofthe area seaward of the rock wall atBinnington Esplanade, Town Beach.

� A review of the adequacy of the rock wallsalong the western coastline of Slade Point,the northern coastline of Blacks Beach andthe section from Dolphin Heads to Eimeoshould be undertaken. The review shouldexamine both the structural integrity andthe potential for overtopping of the wallsduring a storm event with a 100-yearreturn interval.

Avoiding further development inareas prone to erosion and/orstorm tide inundationA number of coastal areas within the studyregion have existing development locatedwithin the erosion prone area and/or areparticularly susceptible to storm tideflooding. These include:

� The Illawong Beach Resort adjacent to theShellgrit Creek entrance. It is recommendedthat the density of development shouldnot be increased in this area.

� The foreshore along the northern sectionof Blacks Beach. In some locations,housing has been constructed seaward ofthe natural coastline. Therefore, wherepossible, a program of acquisitions or therelocation of buildings to the landwardside of affected properties should beencouraged. Further development of high-density land uses such as holidayapartments should be carefully considered.

� At the eastern end of Eimeo Beach anumber of freehold properties are locatednear the end of the sand spit and close tothe tidal creek entrance. Where possible aprogram of acquisition of these propertiesshould be undertaken to convert theprivate freehold land to an open spacedesignation.

� The caravan park at the southern end ofBucasia Beach. It is recommended that noincrease in the density of development bepermitted in this area.

Mitigation of storm tide hazardTo protect against storm tide inundation, thedune system along Far Beach and TownBeach should be carefully managed andenhanced where possible.

Vegetation conservationMost of the native vegetation associationswithin the study region have beenextensively disturbed. Remaining vegetationtypes could be preserved by incorporatingrelatively small areas of high habitat diversityin a series of green conservation corridorsshaped as a ‘T-square’ incorporating acoastal strip and a riparian zone.

Coastal zone preservation areas could includeSlade Bay, Sandringham Bay and DalrympleBay T-square green corridors. Of these, theSlade Bay corridor lies within the study area.The Slade Point dune area and MountBassett rainforest have high conservationvalues and have already been set aside forconservation purposes. The incorporation ofsites at McCreadys Creek, Andergrove, SladeBay, Slade Point, Harbour Beach and MountBassett into a large group will result in amore resilient and diverse unit forconservation.


Australian Bureau of Statistics 1999, Queensland Year Book,Government Printer, Brisbane.

Australian Institute of Aboriginal and Torres Strait Islanders Studies1994, Encyclopedia of Aboriginal Australia: Aboriginal andTorres Strait Islander History, Society and Culture, AboriginalStudies Press, Canberra.

Ball, D. 1998, Personal communication, Department of Environmentand Heritage, Mackay.

Bath, A.T. 1957, ‘The Mackay cyclone of 21st January 1918’, Aust.Met. Mag. pp. 1945–59.

Batianoff, G.N. and Franks, A.J. 1997, Mackay Coast: Vegetation,Floristics and Conservation: Inventory, Management andRecommendations, Department of Environment, Indooroopilly.

BBW 1984, Extreme Water Level Study Addendum — Extreme WaveHeight Frequencies, prepared by Blain Bremner and Williams PtyLtd for D.B.C.T.-U.D.C. Joint Venture, Half Tide Tug Harbour,January.

BBW 1983, Tropical Cyclone Spectral Wave Modelling Study,prepared by Blain Bremner and Williams Pty Ltd for D.B.C.T.-U.D.C. Joint Venture, Half Tide Tug Harbour, September.

BPA 1985, Storm Tide Statistics: Mackay Region, report prepared byBlain, Bremner and Williams Pty Ltd for the Beach ProtectionAuthority, Queensland.

BPA 1983, Sediment Transport Investigation For a Section of CoastNear Eimeo, North of Mackay, Beach Protection Authority,Queensland.

Bruun, P. and Schwartz, M.L. 1985, ‘Analytic prediction of beachprofile change in response to a sea-level rise’, Zeitschrift fürGeomorphologie, N.F., Suppl. Bd. 57, pp. 33–55.

Bureau of Meteorology 1999, ‘Climate variability and El Niño’[Online]. Available:http://www.bom.gov.au/climate/glossary/elnino/elnino.shtml[1999, 26 July].

Bureau of Meteorology 1996, Wind Waves Weather — Queensland,Boating weather series, Department of the Environment, Sportand Territories, Australian Government Publishing Service,Canberra.

Bureau of Meteorology 1965, Climate of Pioneer Region 13 —Queensland, Commonwealth of Australia.

Callaghan, J. and Power, S. (submitted), ‘Long-term Changes in theOccurrence of Damaging Cyclonic Storms in Tropical andSubtropical Eastern Australia’, submitted to the AustralianMeteorological Magazine.

Commonwealth of Australia 1996, A Directory of Important Wetlandsin Australia, 2nd edn, Australian Nature Conservation Agency,Canberra.

Cresswell, G. 1987, The East Australian Current, CSIRO Division ofOceanography Marine Laboratories Information Sheet No. 3,June 1987.

DEH 1998, Wave Data Recording Program Mackay Region1975–1996, Department of Environment and Heritage,Brisbane.

Delft Hydraulics 1999, Unibest-CL V 5.01 for Windows, User Manual,April 1999.

Department of Harbours and Marine 1986, Port and HarbourDevelopment in Queensland 1824– 1985, Department ofHarbours and Marine, Brisbane.

Department of National Development 1970, Climate —Burdekin–Townsville Region, Queensland, Resources Series,Government Printer, Canberra.

Department of National Development 1965, Climate — FitzroyRegion, Queensland, Resources Series, CommonwealthGovernment Printer, Canberra.

Department of Northern Development and Queensland Departmentof Commercial and Industrial Development 1974, Resources andIndustry of the Mackay Region, Australian GovernmentPublishing Service, Canberra.

DHI 1998, MIKE21 User Guide and Reference Manual, DanishHydraulics Institute, Copenhagen.

DPI 1995, Report on Investigation of Terrestrial Geology, MackayCoast, prepared by the Water Resources Section, Department ofPrimary Industries for the Beach Protection Authority.Unpublished.

GHD 1998, Pioneer River Tidal Reaches Study of Sand and GravelExtraction, prepared by Gutteridge Haskins and Davey Pty Ltd forthe Department of Environment, Queensland.

Goda, Y. 1988, ‘On the methodology of selecting design waveheight’, Proceedings 21st International Conference on CoastalEngineering, ASCE, pp. 899–913.

Gornitz, V. and Lebedeff, S. 1987, ‘Global sea-level changes duringthe past century’, in Sea-level Fluctuation and Coastal Evolution,eds D. Nummedal, O. Pilkey and J. Howard, Society of EconomicPalaeontologists and Mineralogists, special publication no. 41,3–16.

Gourlay, M.R. and Hacker, J.L.F. 1986, Pioneer River EstuarySedimentation Studies, Department of Civil Engineering,University of Queensland, St Lucia, Queensland.

Gray, W.M. 1979, ‘Hurricanes: Their formation, structure and likelyrole in the tropical circulation’, in Meteorology Over TropicalOceans, ed. D.B. Shaw, Royal Meteorological Society, JamesGlaisher House, Grenville Place, Bracknell, Berkshire, RG12 1BX,pp. 155–218.

Bibliography


Gray, W.M. 1968, ‘A global view of the origin of tropical disturbancesand storms’, Monthly Weather Review, 96, pp. 669–700.

Harper, B.A. 1998, Storm Tide Threat in Queensland: History,Prediction and Relative Risks, Queensland Department ofEnvironment and Heritage, Brisbane.

Harper, B.A., Sobey, R.J. and Stark, K.P. 1977, Numerical Simulationof Tropical Cyclone Storm Surge Along the Queensland Coast —Parts I to X, Department of Civil and Systems Engineering, JamesCook University, Townsville.

Hegarty, R.A. 1983, Results of a Continuous Profiling Survey in theMackay Area, Geological Survey of Queensland, Record1983/19 (unpublished).

Henderson-Sellars, A., Zhang, H., Berz, G., Emanuel, K., Gray, W.,Landsea, C., Holland, G., Lighthill, J., Webster, P. and McGuffie,K. 1998, ‘Tropical cyclones and global climate change: A post-IPCC assessment’, Bulletin of the American MeteorologicalSociety, Vol. 79, No. 1, January 1998, pp. 19–38.

Holland, G.J. 1993, ‘Ready reckoner’, chapter 9, Global Guide toTropical Cyclone Forecasting, WMO/TC-No. 560, Report No. TCP-31, World Meteorological Organisation, Geneva.

Hopley, D. (ed.) 1983, Australian Sea-levels in the Past 15 000Years, Department of Geography, James Cook UniversityMonograph Series, pp. 93–104.

Institution of Engineers, Australia 1993, At What Price Data?National Committee on Coastal and Ocean Engineering,November.

IPCC 1996, Climate change 1995 — impacts, adaptations andmitigation of climate change: scientific-technical analyses,contribution of Working Group II to the Second AssessmentReport of the Intergovernmental Panel on Climate Change,Cambridge University Press, ISBN 0 521 56437 9, 879 pp.

IPCC 1995, Climate Change 1995 — The Science of Climate Change,Intergovernmental Panel on Climate Change, CambridgeUniversity Press, Cambridge.

Jensen, A.R., Gregory, C.M., and Forbes, V.R. 1966, Geology of theMackay 1:250 000 Sheet Area, Queensland, Bureau of MineralResources Report 104.

Jones, M.R. 1987, Nearshore Sediments and Distribution Patterns,Mackay Coast, Queensland Department of Mines Record Series,1987/25 (unpublished).

Kerr, J. 1980, Pioneer Pageant — A history of the Pioneer Shire,Pioneer Shire Council, Mackay.

Kinhill Pty Ltd 2000, Overview of Fluvial Supply of Sediments to theQueensland Coast and the Impact of Water Resources Structures,prepared for the Queensland Environmental Protection Agency.

Kinhill Cameron McNamara 1994, Coastal Protection StrategyPreparation of Guidelines for Assessing Buffer Zone Widths,prepared for the Department of Environment and Heritage,Queensland.

Larson, M. 1996, ‘Model of beach profile change under randomwaves’, J. Waterway, Port, Coastal and Ocean Eng., Vol. 122, No.4, July/August 1996.

Larson, M. and Kraus, N.C. 1989, SBEACH: Numerical Model forSimulating Storm-induced Beach Change, Report 1: Empiricalfoundation and model development, United States Army Corpsof Engineers, Technical Report CERC-89-9.

Lewis, G. 1973, A History of the Ports of Queensland: A Study inEconomic Nationalism, University of Queensland Press, St Lucia,Queensland.

Lourensz, R.S. 1981, Tropical Cyclones in the Australian Region July1909 to June 1980, Department of Science and Technology,Bureau of Meteorology.

Mackay City Council 1999, Transitional Planning Scheme, MackayCity Council, 21 May 1999.

Mackay Port Authority 2000, Slade Point Dune and Wetland Complex- Objection to the proposed listing in the register of the NationalEstate – Additional Information, unpublished.

Mackay Port Authority 1998, Annual Report 1997–98, Mackay PortAuthority, Mackay.

Mackay Tourism and Development Bureau 1998, Statistical profile ofthe Mackay Region, Mackay Tourism and Development Bureau,Mackay.

Masselink, G. and Lessa, G. 1995, ‘Barrier stratigraphy on themacrotidal central Queensland coastline, Australia’, Journal ofCoastal Research, Vol. 11 No. 2, pp. 454–477.

Masselink, G. and Short, A.D. 1993, ‘The effect of tide range onbeach morphodynamics and morphology: A conceptual beachmodel’, Journal of Coastal Research, Vol. 9 No. 3, pp. 785–800.

Moore, H.A. 1978, The Mackay Harbour Story, Mackay HarbourBoard, Mackay.

Nicholls, N. 1992, ‘Historical El Niño/Southern Oscillation variabilityin the Australian region’, in El Niño, Historical and PaleoclimateAspects of the Southern Oscillation, eds H.F. Diaz and V. Magraf,Cambridge University Press, Cambridge, UK, pp. 151–174.

Nicholls, N., Landsea, C., and Gill, J. 1998, ‘Recent trends inAustralian region tropical cyclone activity’, Meteorol. Atmos.Phys. 65, pp. 197–205.

Oliver, J. 1973, ‘The climatology of Mackay and its area’, Symposiumon Water in the Mackay Region, Mackay, May 1973, WaterResearch Foundation of Australia.

Partridge, I. (ed.) 1994, Will it rain?: the effects of the SouthernOscillation and El Niño on Australia, Department of PrimaryIndustries, Brisbane.

PCTMSL 1999, Permanent Committee on Tides and Mean Sea-levelCircular 43, Defence Publishing Service, Wollongong, May.

Power, S., Casey, T., Folland, C., Colman, A. and Mehta, V. 1999,Inter-decadal Modulation of the Impact of ENSO on Australia,Climate Dynamics, Vol. 15, pp. 319–324.

Proh, D.L. and Gourlay, M.R. 1997, ‘Interannual climate variationsand tropical cyclones in the eastern Australian region’,Combined Australasian Coastal Engineering and PortsConference, Christchurch, NZ, pp. 681–686.

QASCO Surveys Pty Ltd 1998, Mackay Coast PhotogrammetricAnalysis, report prepared for the Department of Environment,January 1998.


Queensland Department of Local Government and Planning 1998,Census Report Queensland, Queensland Department of LocalGovernment and Planning, Brisbane.

Queensland Transport 1999, Tide Tables and Boating Safety Guide,Queensland Government Printer, Brisbane.

Rankine and Hill Consulting Engineers 1971, Mackay RegionalStudy: Land Use and Demography Forecasts, Rankine and HillConsulting Engineers, Brisbane.

Sattler, P.S. and Williams, R.D. (eds) 1999, The Conservation Statusof Queensland’s Bioregional Ecosystems, EnvironmentalProtection Agency, Brisbane.

Sobey, R.J., Harper, B.A. and Stark, K.P. 1977, Numerical Simulationof Tropical Cyclone Storm Surge Along the Queensland Coast,Research Bulletin CS14, Department of Civil and SystemsEngineering, James Cook University, Townsville.

Stephens, A.W. 1993, Evolution of the Proserpine Coastal Plains,Marine and Coastal Geology Project Report 66/2, GeologicalSurvey of Queensland, Department of Minerals and Energy,Brisbane, prepared for the Department of Environment andHeritage.

Toghill, J. 1984, Ghost Ports of Australia, Macmillan, SouthMelbourne.

van Rijn, L.C. 1989, Handbook on Sediment Transport by Currentsand Waves, Delft Hydraulics, Report H461.

Walker, D.J. 1989, ‘An efficient wave hindcasting model’, 9thAustralasian Conference on Coastal and Ocean Engineering,Adelaide, 4–8 December 1989, pp. 117–121.

World Meteorological Organization 1998 (17 December), ‘WMOAnnual Statement on the Global Climate’ [Online]. Available:http://www.wmo.ch/web/Press/Press626.html [1999, 26 July].

Zeller, B. 1998, Queensland’s Fisheries Habitats: Current Conditionsand Recent Trends, Department of Primary Industries, Brisbane.


Year Date Scale Flight Area and Run Film No.

1947 22/08/1947 B/W 30000 Hay Point - Shoal Point Key MAP3829

1948 06/12/1948 B/W 30000 Blacks Beach - Mackay Harbour Run 3 SVY495

06/12/1948 B/W 30000 Flat Top Island - Mackay Run 4 SVY495

06/12/1948 B/W 30000 Round Top Island - Mackay City Run 5 SVY495

06/12/1948 B/W 30000 Bakers Creek - Dudgeon Point Run 6 SVY495

06/12/1948 B/W 30000 Shoal Point - Eimeo Run 1 SVY495

06/12/1948 B/W 30000 Slade Point - Eimeo Run 2 SVY495

06/12/1948 B/W 30000 Blacks Beach - Mackay Harbour SVY495

1962 04/08/1962 B/W 12000 Mackay Run 3 Q1270

31/08/1962 B/W 12000 Mackay Run 2 Q1292

31/08/1962 B/W 12000 Mackay Run 3 Q1292

1970 09/04/1970 B/W 4800 Mackay Harbour Run 1 Q2194

09/04/1970 B/W 4800 Harbour Beach Run 2 Q2194

09/04/1970 B/W 4800 Mackay Harbour Run 4 Q2194

09/04/1970 B/W 4800 Mackay Airport Run 10 Q2194

09/04/1970 B/W 12000 Shoal Point Run 1 Q2194

09/04/1970 B/W 12000 Bucasia Run 2 Q2194

16/05/1970 B/W 12000 Blacks Beach Run 4 Q2198

16/05/1970 B/W 12000 Blacks Beach - Slade Point Run 5 Q2198

16/05/1970 B/W 12000 McCreadys Creek Run 6 Q2198



16/05/1970 B/W 12000 Mackay City Run 9 Q2198




16/05/1970 B/W 12000 Backers Airport Run 13 Q2198

12/06/1970 B/W 3000 Slade Point AAM5109

1972 20/04/1972 B/W 8000 Pioneer River - Bakers Creek AAM7005

Appendix A Aerial photography


.1974 27/05/1974 C 12000 Bell Creek - Slade Point Run 17 Q2853

27/05/1974 C 12000 Mackay Harbour - Neils Beach Run 18 Q2854

27/05/1974 C 12000 Shoal Point - Green Island Run 19 Q2854

27/05/1974 C 12000 Bucasia - Williamsons Beach Run 20 Q2854

10/06/1974 C 12000 Alligator Creek - Slade Point Run 16 Q2874

07/09/1974 C 12000 Bell Creek - Slade Point Run 17 Q2880

1977 09/08/1977 C 12000 Bucasia - Williamsons Beach Run 20 Q3432

12/08/1977 C 12000 Alligator Creek - Slade Point Run 16 Q3433



1978 28/11/1978 C 12000 Bucasia - Williamsons Beach Run 20 Q3438



1979 02/08/1979 C 12000 Mackay Harbour - Neils Beach Run 18 Q3695


02/08/1979 C 12000 Bucasia - Williamsons Beach Run 20 Q3695

1981 07/07/1981 C 12000 Alligator Creek - Slade Point Run 16 QP3882

07/07/1981 C 12000 Bell Creek - Slade Point Run 16 QP3882

07/07/1981 C 12000 Mackay Harbour - Neils Beach Run 18 QP3882

07/07/1981 C 12000 Shoal Point - Green Island Run 19 QP3882

07/07/1981 C 12000 Bucasia - Williamsons Beach Run 20 QP3882

1982 29/03/1982 C 12000 Bell Creek - Slade Point Run 17 QP3871


28/04/1982 C 12000 Alligator Creek - Slade Point Run 16 QP4035C

28/04/1982 C 12000 Mackay City - Slade Point Run 17A QP4035C

05/05/1982 C 12000 Shoal Point - Green Island Run 19 QP4032C

13/06/1982 C 12000 Mackay Harbour - Neils Beach Run 18 QP4041C

1985 23/06/1985 C 12000 Shoal Point - Green Island Run 19 QP4468

25/06/1985 C 12000 Alligator Creek - Slade Point Run 16 QP4460

25/06/1985 C 12000 Bell Creek - Slade Point Run 17 QP4460

25/06/1985 C 12000 Mackay Harbour - Neils Beach Run 18 QP4460


14/07/1985 C 50000 Alligator Creek - Green Island Run 5 QP4496

1990 09/06/1990 C 50000 Kelvin - Slade Pt Run 4 Q4901

09/06/1990 C 50000 Mount Canven - Shoal Point Run 5 Q4901

09/06/1990 C 50000 Slade Point - Mount Jumper Run 6 Q4901


1991 26/06/1991 C 12000 Alligator Creek - Slade Point Run 16 Q4894

26/06/1991 C 12000 Alligator Creek - Slade Bay Run 17 Q4894

26/06/1991 C 12000 East Point - Pioneer River Run 17A Q4894

26/06/1991 C 12000 Sandringham Bay - Bakers Creek Run 17B Q4894

26/06/1991 C 12000 Slade Island - Green Island Run 18 Q4894

26/07/1991 C 12000 Bucasia - Green Island Run 19 Q4897

26/07/1991 C 12000 Bucasia - Sand Bay Run 20 Q4896

1993 19/06/1993 C 12000 Alligator Creek - Slade Point Run 16 Q5070

19/06/1993 C 12000 Alligator Creek - Slade Bay Run 17 Q5070

19/06/1993 C 12000 East Point - Pioneer River Run 17A Q5070

19/06/1993 C 12000 Sandringham Bay - Bakers Creek Run 17B Q5070

20/06/1993 C 12000 Slade Island - Green Island Run 18 Q5070

20/06/1993 C 12000 Bucasia - Green Island Run 19 Q4651

20/06/1993 C 12000 Bucasia - Sand Bay Run 20N Q5070

25/06/1993 C 12000 Alligator Creek - Slade Bay Run 1 QPC4947

25/06/1993 C 12000 Mackay - Shoal Point Run 2 QPC4947

25/06/1993 C 12000 Slade Island - Shoal Point Run 3 QPC4947

25/06/1993 C 12000 Bakers Creek - Mackay Run 4 QPC4947

17/08/1993 C 12000 Kelvin - Slade Point Run 4 Q5149

17/08/1993 C 50000 Mount Canven - Shoal Point Run 5 Q5149

17/08/1993 C 50000 Slade Point - Mount Jumper Run 6 Q5149

15/12/1993 C 12000 Kelvin - Slade Point Run 4S Q5241

1996 18/04/1996 C 12000 Pioneer River Run 17A QPC5209

1997 29/10/1997 C 12000 Alligator Creek - Slade Bay Run 16 QAP5419

01/11/1997 C 12000 Alligator Creek - Slade Point Run 17 QAP5420

01/11/1997 C 12000 Slade Island - Green Island Run 18 QAP5420

01/11/1997 C 12000 Bucasia - Green Island Run 19 QAP5420

01/11/1997 C 12000 Bucasia - Green Island Run 20 QAP5420


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