re proposed amendment no 55 to kempsey shire council’s ... · re-shaping of the beach dune system...
TRANSCRIPT
Re Proposed Amendment No 55 to Kempsey Shire
Council’s Local Environmental Plan 1987
Submission from The Friends of South West Rocks.
This submission presents information which shows that Kempsey Shire Council, in preparing
Draft Amendment No 55 to Kempsey Shire Council LEP 1987, has failed in its legal
duty to take into account the aims of State Environmental Planning Policy No 71 Coastal
Protection and the matters specified in cl 8. In particular, the Council has failed to
take into account the effects of climate change and its impact on flooding and
draining and has failed to adequately address measures to conserve a threatened
species listed as vulnerable under the Threatened Species Conservation Act 1995
(NSW).
Date 6 July 2009
This submission was prepared by:
Alan Hill; Assoc Dip. Appl. Sc. (Landscape), Ryde College of TAFE (NSI); LTHC., (Ryde
College of TAFE (NSI))
Alan Yuille; B. Arch.; Grad. Dip. HNP. (UNSW); M. Env. Studies, (Macquarie U.);LTHC.,
(Ryde College of TAFE (NSI)); Dip. Ed. (ITATE);
Ian L Armstrong; PhD. (U Otago NZ) B. A. (Hons.) (Macquarie U.); B. Land. Arch.
(USyd);
Contact Details:
Friends of South West Rocks
c/o Alan Hill
P O Box 444, South West Rocks NSW 2431
2
Table of Contents Table of Contents .................................................................................................... 2
Overview of the Area............................................................................................................................4
Executive Summary................................................................................................. 5
Background Information.......................................................................................................................5
Flooding .................................................................................................................................................6
Drainage of the Proposed Development Site.......................................................................................7
Wallum Froglet (Crinia tinula) ............................................................................................................8
Conclusion..................................................................................................................................9
Glossary of Terms ................................................................................................. 11
References.............................................................................................................. 12
List of Reports, Studies and Assessments cited for this submission. ..............................12
1.0 Appendix 1: Background and Site Description .............................................. 13
1.1 Site Description .............................................................................................................13
1.1.1 Catchment description ...........................................................................................................13
1.1.2 Topography of the Subject Land...........................................................................................13
1.1.3 Soil Landscapes......................................................................................................................13
1.1.4 Vegetation communities on the Subject Land .....................................................................14
1.1.5 Is the Subject Land a Wetland?.............................................................................................15
1.2 Outline of the Rezoning and Development Proposal...............................................17
2 Appendix 2: Accommodating Future Climate Change. ................................. 18
3 Appendix 3: Flooding ...................................................................................... 22
3.1 Adequacy of the Flood Study for the Estuary and “Proposed Saltwater”
Development Site. ...................................................................................................................22
3.1.1 Background ............................................................................................................................22
3.1.2 Berm Dynamics......................................................................................................................23
3.1.3 Dune De-stabilization, an Unaddressed Consequence of Climate Change........................23
3.1.4 Flood Study Models...............................................................................................................24
3.1.5 Result of Flood Models .........................................................................................................26
3.1.6 Overland Flooding .................................................................................................................30
3.1.7 Conclusion..............................................................................................................................31
4 Appendix 4: Drainage...................................................................................... 32
4.1 Can the Site be Effectively Drained? .........................................................................32
4.1.1 “Groundwater” or “Water-tables”.........................................................................................33
4.2 Proposed Drainage System..........................................................................................35
4.2.1 Pollution and Drainage ..........................................................................................................37
3
4.2.2 Conclusion..............................................................................................................................38
5 Appendix 5: Impact on Threatened Species Located on Site......................... 39
5.1 Wallum Froglet (Crinia tinula)...................................................................................39
5.1.1 Distribution and Abundance on the Study Area ..................................................................39
5.1.2 Disturbance and the Wallum Froglet....................................................................................40
5.1.3 Threats to the Wallum Froglet related to Development ......................................................41
Table Of Figures
Figure 1 Catchment outlined in red with land proposed for rezoning in yellow ................................4
Figure 2 Saltwater Lagoon ........................................................................................................................10
Figure 3 Photo of site taken Feb 2009, clearly showing wetland species regenerating following
disturbance and standing water......................................................................................................15
Figure 4 Vegetation mapped by Kendall and Kendall ..........................................................................16
Figure 5 Proposed land to be rezoned based on 3.0m AHD contour ..................................................17
Figure 6 Photo of Dune Regression with creek mouth in the background 25 May 2009. ...............24
Figure 7 Photo of berm at or near 3.0m AHD........................................................................................26
Figure 8 Flood model for 100 year ARI with berm height at 3.0m AHD...........................................28
Figure 9 Flood model for Probable Maximum Flood with a berm height of 2.0m AHD ................29
Figure 10 Photo of flooding and ponding across the site taken 23 May 2009, with lagoon level at
1.84m AHD .........................................................................................................................................30
Figure 11 Site conditions at time of Hydrogeological Survey ..............................................................33
Figure 12 Photo shows surface ponding above the 3.0m AHD contour .............................................35
Figure 13 Photo of drains “swales” on subject land. .............................................................................36
Figure 14 Photo shows vigorous regeneration following disturbance (“resilience”)........................42
4
Submission Re the Proposed Amendment 55 to Kempsey Shire
Council’s Local Environmental Plan, 1987 to Rezone Land at South
West Rocks for Housing.
Figure 1 Catchment outlined in red with land proposed for rezoning in yellow
Overview of the Area
(See: Appendix 1 1.1 for a more detailed site description)
South West Rocks’ eastern catchment has a total area of 8.9 Sq km. The land
proposed for rezoning (the “subject land”) is 110 ha and is shown in the centre of this
photo. It occupies 12.5% of the total catchment. It has a polluted, abandoned fuel
depot located on the northern boundary.
Saltwater Lagoon, and the listed SEPP 14 wetland, are adjacent to, and east of, the
subject land. They have an area of 104ha, or 12% of the catchment. Saltwater Lagoon
is an Intermittently Closed and Opened Lake or Lagoon (ICOLL) and listed on
Schedule 1 of SEPP 71. The lagoon is a perched swamp, with water levels typically
between 1.5m and 1.8m, but occasionally increasing to 2.2m, above average sea level.
Saltwater Creek, which connects the lagoon to the sea, is blocked by a sand berm
more than 70% of the year. Dynamic coastal processes determine the height of the
sand berm (or sand bank) at the mouth of Saltwater Creek.
5
Executive Summary
Background Information
Kempsey Shire Council has applied to the Minister for Planning to amend the
Kempsey Local Environment Plan (KLEP) 1987 (Amendment No 55) in order to
develop an area of housing, to be known as “Saltwater”, at South West Rocks.
We believe there are also two projects awaiting the Minister for Planning’s approval
under part 3A of the Environmental Planning and Assessment Act 1979 (“EPA Act”)
relating to this land.
We draw to the attention of the Minister for Planning cl 7 of State Environmental
Planning Policy No 71 Coastal Protection which applies to the subject land. Clause 7
requires a council when preparing a draft LEP to take into account matters specified
in clause 8 of SEPP 71. We submit that Kempsey Shire Council has failed to
discharge this legal requirement.
In particular:
1. The Council failed to take into account the aims of the Policy, as required by
cll 7 and 8 of the Policy. The aims of the SEPP 71 are commendably specific
and include in cl 2(1)(j) “to manage the coastal zone in accordance with the
principles of ecologically sustainable development” (as defined in the
Protection of the Environment Administration Act 1991 (NSW) s 6(2)). This
requires inter alia consideration of inter-generational equity and
“fundamental” consideration of biodiversity conservation and ecological
integrity. It also requires consideration of the precautionary principle. We
submit that consideration of the precautionary principle leads to the
conclusion that it is triggered in this matter, requiring a particular method of
decision-making which the Council clearly failed to understand or apply.
2. The Council has failed to take into account the following matters specified in
cl 8 of the Policy:
• Measures to conserve animals (within the meaning of the Threatened
Species Conservation Act 1995) and plants (within the meaning of that
Act), and their habitats (cl 8(g)); especially the Wallum Froglet (Crinia
tinula) which is listed as vulnerable under Sch 2 of the Act.
• The likely impact of coastal processes and coastal hazards on development
and any likely impacts of development on coastal processes and coastal
hazards (cl 8(j))
• The likely impacts of development on the water quality of coastal
waterbodies (cl 8(m))
We submit that if the Minister were to make the LEP on the information provided by
Council, the Minister would be in legal error
6
The main issues addressed in this submission are Flooding, Drainage
and the Wallum Froglet Note
AHD The term Australian Height Datum (AHD) refers to the mean sea level. In
1971 the AHD was set at zero, using the mean sea levels for 1966-1968. It
is used in this submission and throughout the various documents referenced.
Flooding
(See: Appendix 3 for more detail)
In May 2009, South West Rocks experienced a major storm event. This storm caused
re-shaping of the beach dune system on Main Beach, and deposited large amounts of
sand and debris in the mouth of Saltwater Creek. This sand and debris caused a
“berm”, of approximately 3.0m AHD, to build up and block the creek, which is the
outlet to Saltwater Lagoon. The berm height is a critical factor for potential flooding.
“ …the entrance sand berm conditions were found to be critical in predicting
flood levels within the creek and lagoon system.” (The Estuary Management
Plan for Saltwater Creek & Lagoon (EMP) section 2-6, end of 2nd paragraph)
The Local Environmental Study (LES) recommended, and Council adopted,
development above the 3.0m AHD contour within the subject land. This is a crucial
matter and forms the basis for the hydrological studies which underpin the
proposed amendment.
Council told the community that it had taken into account the consequences of
predicted climate change when it made its decision to rezone this land. We submit
that, given Council’s reasoning, the Council manifestly misunderstood its legal duties
in this respect. Given the serious threats to the environment and community of
climate change, and scientific uncertainty as to the environmental damage, the
precautionary principle should be applied. This requires, amongst other things, that
the decision maker must (a) assume that the threat is no longer uncertain but is a
reality, and (b) retain some margin for error until all the consequences of the decision
to proceed are known.
The subject land is low lying, generally between the 1.5m AHD and 4.5m AHD
contours, and adjacent to Saltwater Lagoon.
The recommendation to allow development down to the 3.0m AHD contour, within
the subject land, appears to be based on recommendations contained in The Saltwater
Lagoon and Saltwater Creek Catchment Stormwater Management Strategy (SMS)
WBM Oceanics Nov 2006 and Saltwater Creek Estuary Management Plan (EMP)
WBM Oceanics 2006:
“It has been assumed that development would be restricted to areas beyond a 50m buffer from the estimated 3.0m AHD contour adjacent to Saltwater Lagoon and Creek. This buffer accommodates existing lagoon flooding (up to the 100 year ARI event) and changes to the lagoon water level dynamics associated
with future sea level rise.” (SMS WBM 2006 pg 3-2) (our emphasis)
7
“…Assuming a worst case scenario (as recommended in [the discussion in
their report]) and no entrance management, a berm level of RL 3.0m AHD
would be the most appropriate design conditions for planning purposes for
the year 2100.” (EMP section 7.10.3 pg 7-36). (our emphasis)
A berm height of 3.0 AHD had already been predicted, under present day
conditions, in the Saltwater Creek Estuary Process Study by Manly Hydraulics
Laboratory, 2002(MHL, 2002). The LES quotes the study, and says of it:
“This report defines the existing condition of and interaction between estuary
processes in the Saltwater creek estuary.” (LES, section 4.3, pg 35) (our
emphasis)
also
“ MHL predicted that under [a] strategy of allowing the berm to open
naturally, the berm could reach a height of approximately 3 m AHD. Allowing
the berm to reach this height could increase the flood risk to approximately 4
m AHD” (LES, section 4.3, pgs 36)
It was predicted, and it has now happened, that under present day climatic conditions
the berm can reach 3.0m naturally.
With sea level rise due to climate change, it is predicted the berm will go
significantly higher than the present height of 3.0m AHD
Council has used 3.0m AHD as sufficient to satisfy a “worst case scenario”. A
berm height of 3.0m AHD is already here. This land will flood.
Drainage of the Proposed Development Site
(See Appendix 4 for more detail)
The Drainage Proposal does not address Climate Change
We believe that the scheme proposed to drain the site is poorly resolved, based on
misleading data and extrapolated from the best-case scenario. The recommendations
proposed in the LES, in regard to drainage, have not addressed the consequence of
predicted sea level rise due to climate change. The proposal to use “wick” drains has
the potential to irreversibly damage the lagoon. (Appendix 4)
The drainage modeling was done by Douglas Partners, and presented in their
Hydrogeological Assessment 2007. The data was collected from the site during July
and August 2007, the driest months of the year, toward the end of the longest
recorded drought in Australia. The creek mouth was closed and the lagoon was at a
relatively low 1.2m AHD. This data was then used to model a complex series of
underground drains, above ground open drains, swales and most alarmingly by the
use of “wick drains” to drain the site. We believe we can show that these measures
could not, and would not, effectively drain the site under present climatic conditions.
Therefore it certainly will not cope with the predicted rising groundwater associated
with sea level rise and consequent higher water levels in the lagoon.
8
Potential Impact on the SEPP 14 wetland by the Drainage Proposals
We are greatly concerned that the drainage works, as presented in the LES, have the
potential to irreversibly damage, or destroy, the adjacent Sepp 14 wetland. The
drainage study found that water “mounds” across the site over impervious layers of
“indurated sands”. The proposal, contained in the Drainage Assessment, (Douglas
Partners, page 28) is to penetrate the impervious layer, and construct vertical or
“wick” drains, to drain water to a lower aquifer.
The water table under the subject land is directly connected to the SEPP 14 listed,
Saltwater Lagoon, a “perched” swamp. Draining the subject land could adversely
affect water levels in the lagoon. Douglas Partners caution:
“care may [would] be required if penetrating the indurated layer on the
eastern part of site near W3 and CPT101 to ensure that penetrating (sic) layer
does not excessively drain the upper perched layer”. (Douglas Partners 2007,
(written twice) page 28)
Have “wick drains” been used elsewhere so close, and adjacent to, other SEPP 14,
perched swamp wetlands? If so what was the result?
The Precautionary Principle should apply.
Wallum Froglet (Crinia tinula)
(See: Appendix 5 for more detail)
The Wallum Froglet was located on this site in April 2004. It is listed in Schedule 2 of
the Threatened Species Conservation (TSC) Act, 1995, as “Vulnerable”. The Fauna
Survey referenced in the LES notes (LES appendix d section 5.1 Wallum Froglet)
“The Wallum Froglet was located across a large part of the study area….”
“…Due to the large area of known habitat, the study (sic) is considered likely
to contain significant habitat.” (Their emphasis not ours)
"Clearing of native vegetation" has been listed as a KEY THREATENING
PROCESS in Schedule 3 of the TSC Act.
The “study area” is noted as having been disturbed:
“The disturbance history is likely to have created habitats that may be more
similar to early successional stages of this species habitat.” (LES 5.1
Appendix A, of Appendix d)
The habitat described is Wetland Heath vegetation. Wetland Heath communities are
naturally subjected to frequent disturbance from flooding, drying and burning. They
9
have a very high degree of resilience to disturbance. It could be anticipated that if the
disturbance factor were removed this community would quickly recover in structure,
form and species diversity.
The LES appears to confuse clearance with disturbance when it recommends that
increasing the area to be excluded from development is not justified.
“Option 3 has used the 4.0m AHD contour as the basis for habitat retention.
As can be seen from fig 5.2, the additional area encompassed by Option 3 is
primarily that area which has been previously cleared. It is considered that
the quality of the additional habitat provided by including the Option 3 area
as retained habitat would not result in any significant increase in the quality
of habitats already provided by using Option 1.” (Option 1 is to the 3.0m
AHD contour) (LES pg 60)
The LES did not investigate the resilience potential for the subject land, and has
failed in its legal duty to provide adequate information for the Council to form
an opinion on this matter.
(Note: The Wallum Froglet was identified across the subject land in April 2004. Why
is the habitat still being extensively disturbed as recently as 2009?)
Conclusion
A quote from one of the studies accurately describes the issues faced by the SEPP 14
and SEPP 71 listed Saltwater Lagoon:
“Based on the measured nutrient concentrations and extent of algal growth
within the estuary, it is considered that Saltwater Creek and Lagoon system is
already at or exceeding its natural capacity to accept catchment loads.
Further increases in the amount of nutrients and other pollutants discharged
to the system may result in catastrophic changes to estuarine ecology, which
may be very difficult (if not impossible) to reverse. Over-development of some
ICOLL catchments, particularly around Sydney, has resulted in highly
degraded estuarine systems possessing little ecological value (eg Manly
Lagoon, Curl Curl Lagoon, Terrigal Lagoon).” (EMP 2006 pg 2-10)
The subject land is the major buffer to Saltwater Lagoon. It surrounds, filters
and protects the lagoon from the polluted and nutrient laden run-off, which
flows from the increasingly urbanized catchment of South West Rocks. We
believe that the proposal to develop 70ha of this 110ha, with up to 860 dwellings,
will effectively destroy Saltwater Lagoon, a SEPP 71, Schedule 1 listed, ICOLL.
10
We also believe that Council has:
1. failed in its legal duty to accurately assess the proposed changes to their
Local Environment Plan under ESD principles.
2. used incorrect information in their flood predictions to address sea level
rise.
3. not adequately addressed the issues of drainage for present conditions let
alone sea level rise.
4. not exercised due diligence, when considering the Wallum Froglet, under
the Threatened Species Conservation Act 1995
We urge the minister to reject the proposed amendment to Kempsey
Shire Councils LEP, and any developments relating to this land
under consideration under Part 3A of the EPA Act.
Figure 2 Saltwater Lagoon
11
Glossary of Terms
AHD The term Australian Height Datum (AHD) refers to the mean sea
level. In 1971 the AHD was set at zero, using the mean sea levels for
1966-1968. It is used in this submission and throughout the various
documents referenced.
ARI Average Recurrence Interval: the long-term number of years
between the occurrence of a flood as big as (or larger than) the
selected event.
Design Flood A hypothetical flood representing a specific likelihood of
occurrence.
Floodplain Land adjacent to a river, creek or estuary and is periodically
inundated due to floods. The floodplain includes land that is
susceptible to inundation by the probable maximum flood (PMF)
event.
PMF Probable Maximum Flood An extreme flood event to be the
maximum flood likely to occur
12
References
List of Reports, Studies and Assessments cited for this submission.
Many of the following reports were located on Kempsey Shire Council’s website, and
can be accessed through the following link: http://saveswr.net/
Kempsey Local Environmental Plan (LEP) 1987 (Amendment No. 55). Clause 65
Local Environmental Study (LES) Saltwater Developments Area Phillip Drive & Bell
O’Connor Street South West Rocks, (Connell Wagner Rev 8 Feb 2008)
Saltwater Creek Flood Study Final Draft Report (WBM Oceanics, 28 June 2006)
The Estuary Management Plan for Saltwater Creek & Lagoon South West Rocks,
Final report (WBM Oceanics June 2006)
Saltwater Lagoon and Creek Stormwater Management Strategy, Final Report (WBM
Oceanics, May 2007)
Saltwater Creek Estuary Process Study, (Manly Hydraulics Laboratory 2002.)
Hydrogeological Assessment Proposed residential Subdivision off Phillip Drive South
West Rocks, (Douglas Partners, 2007)
Preliminary Assessment Residential Subdivision “Saltwater” Plannit Consulting
March 2009
Saltwater Creek Catchment Flora and Fauna Study South West Rocks Kendall and
Kendall, 13 Feb. 2003
Preliminary Assessment Residential Subdivision “Saltwater” under Part 3A Plannit
Consulting March 2009
Ecosystem Resilience and the Restoration of Damaged Plant Communities: A
Discussion Focusing on Australian Case Studies” PHD Thesis UWS, M. Christine
McDonald August 1996
13
1.0 Appendix 1: Background and Site Description
1.1 Site Description
1.1.1 Catchment description
The catchment for Saltwater Lagoon is shaped, and acts, like a basin. The basin’s
catchment is formed by the Smoky range to the east, Arakoon Rd to the south,
Gregory St to the west and the sand dunes along Main beach to the north. Saltwater
Lagoon is an expression of the water table at the lowest point within the basin.
The subject land is bordered on its northern boundary by abandoned fuel depot sites.
These sites have been identified as having polluted groundwater plumes emanating
from them.
1.1.2 Topography of the Subject Land
The subject land is 110 ha in area. It is low lying, generally between 1.5m and 4.5m
AHD. (Douglas Partners, 2007 pg 3). We calculate that the average gradient is 0.3%,
so is virtually flat.
1.1.3 Soil Landscapes
The subject land contains three swamp landscapes, the Clybucca, Hat Head and Seven
Oaks soil landscapes. (LES pg 27). Acid sulphate soils have been identified as
potentially occurring on the subject land:
“However there is a high potential to encounter acid sulphate soils less than
one metre below ground level along the drainage line between the golf course
and Saltwater Lagoon.” (LES pg 31)
The two main soil types are:
1.1.3.1 Clybucca Soil Landscape
“The Clybucca soil landscape consists of backbarrier muddy swale swamps
and closed depressions overlying Pleistocene sands. Relief is less than one
metre; elevation is less than five metres; and slopes are less than three
percent. This landscape is characterised by organic soils with low wet bearing
strength, sodicity, low subsoil permeability, localised acid sulfate soil
potential, strong acidity, high aluminium toxicity potential and low fertility.
“The Clybucca soil landscape has been associated with a number of
limitations, including poor drainage, high run-on, flood hazard, permanently
high watertables, groundwater pollution hazard, non-cohesive soils, high
foundation hazard and soil fire hazard.” (LES appendix e pg 5)
14
1.1.3.2 Hat Head Soil Landscape
“The Hat Head soil landscape is the dominant landscape of the northern half
of the study site. The Hat Head soil landscape consists of level closed and
open-depressions perched within Pleistocene dunes. Relief is less than one
metre and elevation less than 20 metres. Open depressions may have slopes of
about one per cent, while closed-depressions are slightly concave or flat. A
variant of this landscape is present in the study site as level, backbarrier
beach ridge swale swamps.
Soils associated with the Hat Head soil landscape are organic soils with low
wet bearing strength, high erodibility, low permeability, strong acidity, low
available waterholding capacity and low fertility. The Hat Head soil
landscape has been associated with a number of limitations, including poor
drainage, flood hazard, permanently high watertables, groundwater pollution
hazard, non-cohesive soils and high foundation hazard.”(LES appendix e pg 5)
1.1.4 Vegetation communities on the Subject Land
“Seven vegetation communities have been identified by Peter Parker (2002),
Kendall and Kendall (2003) and Connell Wagner (2005) as occurring on the
study site. These include Mixed Sedge/Heath, Open Forest, Swamp Forest,
Sedgeland, Shrubland, Scribbly Gum Woodland, and Red Gum/Swamp
Mahogany Woodland.” (LES appendix e pg 6)
The two vegetation communities directly affected by clearing for the proposed
development are:
4.2.1 Mixed Sedge Heath
“A wet heath / sedge land community occurs in an area recently slashed or
cleared in the northern sections of the site. Kendall and Kendall (2003)
considered regeneration by native species to be in the early stages and
expected such areas to return to a wet heath – sedgeland complex. This area
becomes inundated after rainfall and is subject to poor soil drainage”. (LES
appendix e pg 6)
“All of the wet heath associations mapped in the study area are recognised as a
regionally vulnerable.” (Kendall and Kendall, 2003 pg 31)
4.2.5 Shrubland
“Shrubland dominated Banksia ericifolia var. macrantha is scattered through
the central and northern parts of the study site and dominates the poorly
drained areas in the south and southeast of the site. The presence of
occasional emergent Swamp Mahogany (E. robusta), paperbarks and other
typical swamp associates suggests the area is subject to poor drainage and
likely to be inundated during prolonged rainfall.” (LES appendix e pg 6)
These vegetation communities are both described as “Wallum Vegetation”. (LES
appendix e fig 4.1):
15
1.1.5 Is the Subject Land a Wetland?
1.1.5.1 Wetland Definition (Dept. Environment and Resource Management Qld
definition, Based on the Ramsar Convention):
“Wetlands are areas of permanent or periodic/intermittent inundation, with
water that is static or flowing fresh, brackish or salt, including areas of
marine water, the depth of which at low tide does not exceed 6 metres. To be
classified as a wetland, the area must have one or more of the following
attributes:
• at least periodically, the land supports plants or animals that are adapted
to and dependent on living in wet conditions for at least part of their life
cycle,
or
• the substratum is predominantly undrained soils that are saturated,
flooded or ponded long enough to develop anaerobic conditions in the
upper layers,
or
• the substratum is not soil and is saturated with water, or covered by water
at some time.”
Based on the definition above, the soil landscape descriptions, the vegetation
descriptions and observation, it is a wetland.
Figure 3 Photo of site taken Feb 2009, clearly showing wetland species
regenerating following disturbance and standing water.
16
Figure 4 Vegetation mapped by Kendall and Kendall
“Illustrates the extent of wetland and watertable dependent communities, the
gazetted SEPP14 boundary and the national park boundary. Ideally this entire
area within the blue boundary [includes most of the subject land] should be
included in the wetland buffer, with the preferred landuse allowing for the
retention of the wet heath, current landuse has degraded but not destroyed the
wet heath associations.” Map 3 (Extracted from Kendall and Kendall 2003)
17
1.2 Outline of the Rezoning and Development Proposal.
The proposal is to change the zoning of the subject land so that 70ha of the 110ha site,
can be developed for housing. The land proposed for development is land generally
between the 3.0m and 4.5m AHD contour.
We understand there are two applications before the Minister for Planning relating to
this land under Part 3A of EP&A Act 1979. One is seeking approval for 463
dwellings on the northern portion and the other for 400 dwellings on the southern
portion.
Figure 5 Proposed land to be rezoned based on 3.0m AHD contour
(From Preliminary Assessment Residential Subdivision “Saltwater” under Part 3A
Plannit Consulting March 2009 Fig 5)
18
2 Appendix 2: Accommodating Future Climate Change.
The following is an extract from The Estuary Management Plan for Saltwater Creek
& Lagoon South West Rocks, Final report (WBM Oceanics June 2006). It provides an
overview for what the current climate change predictions are and some of the
ramifications for coastal areas.
Some of the more recent predictions are more dire than those presented below.
19
20
21
22
3 Appendix 3: Flooding
3.1 Adequacy of the Flood Study for the Estuary and “Proposed Saltwater” Development Site.
3.1.1 Background
In May 2009, South West Rocks experienced a major storm event. This storm
caused re-shaping of the beach dune system on Main Beach, and deposited large
amounts of sand and debris in the mouth of Saltwater Creek. This sand and
debris caused a “berm” of approximately 3.0m AHD to build up and block the
creek, which is the outlet to Saltwater Lagoon.
Council commissioned several hydrological studies. Three of these studies, Saltwater
Creek Flood Study (WBM Oceanics 2006), The Estuary Management Plan for
Saltwater Creek & Lagoon South West Rocks (EMP) (WBM Oceanics 2006) and the
Stormwater Management Strategy (WBM Oceanics, May 2007) discuss and assess in
detail, or in part, the flood potential for the proposed development site.
The Stormwater Strategy has this to say on the subject of flooding.
“It has been assumed that development would be restricted to areas beyond a
50m buffer from the estimated 3.0m AHD contour adjacent to Saltwater
Lagoon and Creek. This buffer accommodates existing lagoon flooding (up to
the 100 year ARI event) and changes to the lagoon water level dynamics
associated with future sea level rise.”
All the studies dealing with the hydrology of the estuary, and the proposed
development site, acknowledge the critical relationship between the entrance berm
height and the flood level across the flood plain. Typical predictions for the current
dynamics of this berm are:
“The berm height at the creek mouth is influenced by wave energy and fluvial
(wind) action, however it is typically in the order of 2m AHD and under
natural processes could get to 3m AHD” (Hydrogeological Assessment”
Douglas Partners, 2007)
“If an entrance management strategy of allowing the berm to open naturally
were to be adopted, then it is possible that the berm may attain a level of
about 3.0m AHD, similar to the berm height on the beach immediately to the
east of the entrance” (Saltwater Creek Estuary Process Study, Manly
Hydraulics Laboratory 2002).
However the information above appears to have been ignored when the LES
recommended, and Council accepted, that development should be allowed down
to the 3.0m AHD contour. Instead they appear to have based their
23
recommendations on the following statement contained in the Estuary
Management Plan.
“Assuming a worst case scenario (as recommended in [the discussion in
their report] and no entrance management, a berm level of RL 3.0m AHD
would be the most appropriate design conditions for planning purposes for
the year 2100.” (EMP WBM 2006 7.10.3 “Impacts of Climate Change on
Flooding” pg 7-36) (our emphasis)
We believe that the facts, as presented, are false and misleading. To suggest that
development above the 3.0m AHD contour within the subject land, allows for the
consequence from sea level rise is false. And to suggest that using a berm height of
3.0m AHD “would be the most appropriate design conditions for planning purposes
for the year 2100” for flood modeling is misleading, as 3.0m AHD is possible and
occurs under current climatic conditions.
3.1.2 Berm Dynamics
The extracts from the EMP (WBM 2006) contained in Appendix 2 give detailed
description of predicted consequences with climate change, in relation to the berm
height at the creeks entrance. Included is the following statement:
“An increase in mean sea level would result in an upward and
landward translation of the ocean beach profile (Bruun 1962, Dean
and Maurmeyer 1983, Hanslow et al 2000) thus causing a net
shoreline recession (ref Fig 7-2). The changed beach processes will
result in a net upward shift in typical berm heights of coastal lake
entrances”. (EMP section 7.10.1 pg 7-34) (our emphasis)
3.1.3 Dune De-stabilization, an Unaddressed Consequence of Climate Change
There may be other significant implications from the climate change predictions as set
out in Appendix 2.
The Creek is confined by a longitudinal barrier dune system, which varies in width
from approximately 100m to 300m, between the beach and Saltwater Creek (see fig 1
appendix 1.1). The recent storms appear to have removed up to 100m width from
some parts of the vegetated dunes (fig 6 below).
What would be the consequences if the dune system is destabilized by fire, storms or
human activity, and so become “mobile dunes”? As outlined in the appendix 2, the
dunes will migrate inland, with the prevailing wind and wave action. The mobile
dunes then have the potential to block much of the creek system, not just the entrance
berm.
24
Figure 6 Photo of Dune Regression with creek mouth in the background 25 May
2009.
3.1.4 Flood Study Models
The WBM Oceanics (2006) Flood Study developed a theoretical model based on
various data sources.
The results from modeling undertaken for the flood study:
“The model shows that the increment of 0.5m on the sand berm crest level is
attenuated in terms of flood levels. For instance, the maximum 100 year ARI
flood levels in Saltwater Lagoon vary from 3.1m AHD to 3.4m AHD,
depending on the adopted entrance condition.” (Flood Study WBM Oceanics
2006 pg 4-4)
The above models were based on berm heights ranging from 2.0m AHD to 3.0m
AHD. That is, based on berm heights suitable under present day climatic
conditions, not for future sea level rise.
The 100 ARI flood for a 3.0m AHD berm is modeled at flooding to the 3.4m
AHD contour
25
Council has determined that it is appropriate to rezone land for housing down to
the 3.0m AHD contour on the subject land.
However Manly Hydraulics Laboratory Estuary Process Study (MHL) goes on to say:
“If an entrance management strategy of allowing the berm to open naturally
were to be adopted, then it is possible that the berm may attain a level of
about 3.0m AHD, similar to the berm height on the beach immediately to the
east of the entrance (this was in 2002). In the event of a significant rainfall
event the likely flood risk is shown in Figure 2.1, which was assumed to
coincide with the 4m contour” (pg 70) (Our emphasis)
Note: the above comment refers simply to a “significant rainfall event”, not to a 100
year ARI event, as modeled in the flood study.
The LES quotes the same MHL study:
“This report defines the existing condition of and interaction between estuary
processes in the Saltwater Creek estuary.” (LES, section 4.3, pgs 35)
During the recent storms, (May 2009), the berm reached a height of
approximately 3.0m AHD, thus confirming the prediction of Manly Hydraulics
Laboratory and Douglas Partners (quoted previously).
The above predictions and the result of the recent (May 2009) storms are in direct
conflict with the following statement from WBM Saltwater Creek and Lagoon
Estuary Management Plan (2006), section: 7.10.3 “Impacts of Climate Change on
Flooding”
“Assuming a worst case scenario (as recommended in [the discussion in
their report and given in appendix 2 of this submission]) and no entrance
management, a berm level of RL 3.0m AHD would be the most appropriate
design conditions for planning purposes for the year 2100.” (our emphasis)
Later the Estuary Management Plan says this under section, 7.10.4 “ Planning
Considerations for Future Climate Change at Saltwater Lagoon”
“Please note that this estuary Management Plan has not made specific
recommendation with respect to Floodplain Risk Management, and the need
to manage flooding risk in the context of future climate change.” (our
emphasis)
26
Figure 7 Photo of berm at or near 3.0m AHD
This photo was taken within minutes of council opening the berm (5.23PM on 25th
May, hence the poor light). The water level in the creek was 1.9 m AHD (Data from
Manly Hydraulics Lab). We estimate 300mm of sand and debris had already been
scraped off the surface and can be seen in the background. The remaining sand is
approximately .6m to .7m above the water level of the creek. We believe the berm
was approximately 3.0m AHD before Council undertook reshaping the berm and
digging the channel.
A request was made to Council to provide us with survey details of the berm, on the
25th
May. Surveying the berm is one of the conditions set out in the “Opening
Procedures” (Saltwater Creek and Estuary Management Plan pg C-6) commissioned
by Council. We were informed that no survey had been conducted.
3.1.5 Result of Flood Models
We have been unable to locate an accurate, independent site survey for the proposed
development site, within the publicly available documents. We note that in the
Hydrogeological Assessment, Douglas Partners (2007) provide some data, which
appears to be relevant:
“The ground surface levels on the northern part of the site fall to the south
and east, toward the creek and lagoon from levels in the range of 4.5m AHD
to 1.5m AHD along the banks of the creek and lagoon.” P4
27
Ground surface levels on the southern parts of the site fall to the north
towards the creek from about 4.0m to 6.0m AHD near the southern boundary
to about 1.5m AHD along the creek banks.” P4
3.1.5.1 Flood Model for 100 year ARI
(see fig 8)
The modeling for the 100 year ARI flood, at a berm height of 3.0m AHD, models a
flood level of 3.4m AHD. The model has many variables, including survey data
provided by the owner. As the land is virtually flat (0.3% gradient, WBM Flood
Study) an inaccuracy of 10 cm in the predicted, or actual flood height, translates
to a horizontal shift of 30 metres for the flood model, or on the ground.
3.1.5.2 Probable Maximum Flood
(see fig 9 )
The Probable Maximum Flood (PMF) model was only provided for the 2.0m
AHD berm height. Even at this, the lowest average height used for modeling, the
model showed flood levels would reach 4.5m AHD. That is, it would cover virtually
the entire northern section, and most of the southern portion, of the proposed
development site with up to 1.5 metres of water. (see fig 9 PMF 2.0m AHD).
We acknowledged that the Flood Study qualifies the use of the PMF as :
“the use of a PMF in a flood study is to provide levels for planning and
evacuation purposes. Great accuracy is not required.” (Flood Study WBM
Oceanics 2006 pg 5-3)
It is interesting to note that the parameters for 2 D modeling of the PMF appears to
stop at the 4.0m AHD contour line. If the graphic had show up to the 5m AHD
contour, the extent of the flooded area depicted would have been significantly greater,
covering most of the proposed development site. That is, as discussed previously, the
subject land and the lagoon edges are essentially the entire floodplain.
In light of climate change prediction the PMF may be a more applicable flood
model for this site than the 100 year ARI model.
28
Figure 8 Flood model for 100 year ARI with berm height at 3.0m AHD
29
Figure 9 Flood model for Probable Maximum Flood with a berm height of 2.0m
AHD
The flood model for the PMF at 2.0m AHD portrays a truncated extent of a Probable
Maximum Flood (PMF). According to the colour coding provided with the model, if
one measured the water depth at the edge of the red line (extent of model) there would
be a vertical edge of water .5m high.
30
No PMF for a 3.0m AHD berm height was presented in the publicly available
documents.
3.1.6 Overland Flooding
The flood study identifies the level to which the lagoon will rise under present day
conditions. It does not identify the volume of water which pools and flows across the
site once the soil is saturated and the water table rises to the surface and higher.
Significant standing and slow flowing water can be observed across the site even
following moderate rain events. The following photo, taken at 4.00PM on 23 May
2009 shows water ponding across the site above the 3.0m AHD contour. Rainfall
records show that there was 5.6mm of rain that day after 9.00AM.
Figure 10 Photo of flooding and ponding across the site taken 23 May 2009, with
lagoon level at 1.84m AHD
The flooding is due to a combination of several factors:
• Saturation of the soil;
• The presence across much of the site of a relatively shallow, low permeability,
indurated sand layer or “coffee rock”;
31
• An increased pressure gradient from water moving down from the
significantly higher surrounding catchment;
• The virtually flat nature of the land (gradient <0.3%)
• Resistance to groundwater flows due to viscosity or friction within the soil;
• The impedance of groundwater flow to the lagoon, due to the “wedge effect”
created by the underlying, relatively dense, saline water layer in the lagoon.
“ ..a short duration rainfall event of around 100mm to 300mm would be
expected to lead to a period of saturation of the ground and ponding of the
surface water in low points, especially where confining layers are present.”
(Douglas Partners (2007) P22)
Note: 100mm to 300mm rainfall events are relatively common in this catchment.
3.1.6.1 Flooding and the Use of Fill on the Proposed Development Site.
Apart from a complex and, in light of the following discussion (Appendix 4:
Drainage), unlikely proposal to drain the site, neither the LES nor LEP make it clear
how they propose to deal with infrastructure and dwellings, located in a floodplain,
with permanently high ground water. This is critical as it is likely that the extent of
flooding may be more extensive than the scenario(s) the LES suggests.
However, the LES appears to provide an opportunity for filling on the subject land:
“Any fill which is imported to the site to provide consolidated bearing above
the flood level must be free of contaminants.” LES, (section 4.1.3 p29)
If it is the intention to fill or partly fill the subject land to accommodate the proposed
development, it has not been clearly stated. The ramifications would be significant in
regard to flooding, drainage, habitat loss and many other issues.
It could be anticipated, for example, that filling a significant proportion of the
floodplain (70 ha) would exacerbate flooding in the remainder of the floodplain. This
has not been modeled.
3.1.7 Conclusion
We believe that Council failed to address the consequences from predicted sea
level rise, associated with climate change predictions in relation to flood
potential, when it made its determination to rezone this land for housing.
32
4 Appendix 4: Drainage
4.1 Can the Site be Effectively Drained?
The Hydrogeological Assessment Proposed residential Subdivision off Phillip Drive,
South West Rocks, was undertaken by Douglas Partners in 2007.
The survey work to assess the site conditions was undertaken in July and August
2007, two of the driest months of the year in this region, and toward the end of
the longest recorded drought in Australia’s history. The lagoon was at a relatively
low level, 1.2m AHD, (nor had it been above this level in the previous 12 months,
data from MHL). From the aerial photo it appears the creek mouth was closed. It
could be anticipated that the groundwater levels from this survey, taken at this
historically dry time, would be at, or near their lowest level and at, or near,
equilibrium relative to the lagoon.
Part of the survey work was to assess the groundwater depths:
“the typical water table depth at the site appears to be in the order of 0.7m to
1.5m depth and provided groundwater levels are maintained below about
0.8m to 1.0m it is considered that construction of houses roads and services
could be undertaken using appropriate engineering which takes into account
the potential reduction in the strength of soil due to Shallow water.”
(Hydrogeological Assessment 2007, pg 24)
“Groundwater depths at the site during the investigation where drainage is
likely to be required (most parts of the site apart from south western portion)
were typically in the range 0.7m to 1.5m (below surface level). It is considered
that a groundwater depth of at least 0.8m is desirable for engineering and
serviceability requirements of the development, so the setting of a drainage
system at a depth in the order of 0.8m to 1.2m would be anticipated”.
(Hydrogeological Assessment 2007, pg 28)
“Groundwater measurements have been taken after periods of dry weather
and are not expected to represent conditions after rainfall” (Hydrogeological
Assessment 2007, pg 22)
It is also interesting to note that in all the photos taken of the site at the time, and
reproduced on page 5 and page 6 of the Hydrogeological Assessment show standing
groundwater at or near the surface (Figure 11).
33
Figure 11 Site conditions at time of Hydrogeological Survey
(July and August 2007) (Pg 5 Douglas Partners)
Note water lying at the surface in these shallow drains, at this the driest time of year
and at the end of the drought.
4.1.1 “Groundwater” or “Water-tables”
Groundwater levels are directly affected by the water level in the lagoon. In turn the
water level in the lagoon is directly affected by the berm height at the creek mouth.
“ It is noted that the management strategy adopted for the sand berm at the
mouth of Saltwater Creek will potentially have a large impact on groundwater
levels, especially in the wetland areas around the lagoon.” (Hydrogeological
Assessment 2007, pg 25) (and, it should be added, the subject land)
“The typical water level in the lagoon, under current climatic conditions, is
1.5m to 1.8m AHD. The creek mouth is artificially opened when the lagoon
reaches between 1.8m to 2.0m.” (EMP pg 6-10). (our emphasis)
34
However data sourced from Manly Hydraulics Laboratory show that on the 16th
Feb 2009 the lagoon reached 2.21m AHD and on 25th
May 2009 it reached 1.91m
AHD.
Water tables are not horizontal, or flat below the ground, instead they are dish
shaped. This can be illustrated using some of the data provided from the bore samples
undertaken to establish the groundwater levels, amongst other things, on the site.
When the lagoon was at 1.2m AHD surface level, the ground water was at:
Surface level Groundwater level Depth below surface
3.0m AHD 2.3m AHD 0.7m
4.0m AHD 3.2m AHD 0.8m
4.45m AHD 3.56m AHD 0.91m
(adapted from data in Table 1 Pg 16 Hydrogeological Assessment 2007,).
When the lagoon is higher, the water table is also higher. The following table shows
what we believe are likely to be groundwater levels when the lagoon is at 2.0m AHD
surface levels, that is, 0.8m higher than when the survey work was undertaken.
Surface level Groundwater level Depth below surface
3.0m AHD 2.3 + .8 = 3.1m AHD At the surface
4.0m AHD 3.2 + .8 = 4.0m AHD At the surface
4.5m AHD 3.56 + .8 = 4.36m AHD 0.14 m
Rain events will quickly flood the site.
The reason the water table is dish shaped is due to several factors:
• partly viscosity, or friction of the water passing through the soil;
• partly the pressure gradient of water moving from higher levels in the
catchment due to gravity;
• and partly the capillary action at the surface of the soil particles drawing the
water up through the soil profile.
35
Figure 12 Photo shows surface ponding above the 3.0m AHD contour
Photo shows water above the surface, and ponding. This photo was taken on late
afternoon, 23 May 2009, with less than 6mm rainfall on that day (although there had
been significant rain on the previous day). The lagoon surface level was 1.84m AHD
(data Manly Hydraulics Lab)
4.2 Proposed Drainage System.
The proposed drainage scheme is a mix of subsurface drains, between 0.8m and 1.2m
below surface levels, open surface drains and constructed wetland / swales between
the development zone and the development exclusion zone. The drainage swales will
therefore be at the 3.0m AHD contour.
“It is however considered that drainage measures will be required to control
increases in the groundwater level due to rainfall events and seasonal
variations in rainfall. This could comprise a network of subsoil drainage set at
about 0.8m to 1.2m below ground surface.” (Hydrogeological Assessment
2007, pg 24)
“The purpose of this drainage system should be to prevent high groundwater
levels after high rainfall, however have limited effect on the groundwater
system under normal conditions. This can be achieved by setting the drainage
at an appropriate level.” (Hydrogeological Assessment 2007, pg 27)
What does appropriate level mean?
36
“Construction of wetlands / swales between the development areas and the
development exclusion zones seems to be a practical option, however
available infiltration will still be limited due to the presence of confining
indurated layers and on the southern parts of the site, shallow clay.”
(Hydrogeological Assessment 2007, pg 26)
The scheme outlined in the Hydrogeological Assessment relies on subsurface drains
to discharge into open swales at the 3.0m AHD contour. As discussed above, under
“Groundwater”, the water table at these swales may, under present day conditions,
often be at, or near, the surface, that is, 3.0m AHD. The drainage proposal is to set
drains at various depths to keep groundwater below .8m below the surface. We
assume this to mean that drains at the 3.0m AHD surface contour would be at 2.2m
AHD (3.0m-.8m), at the 4.0m AHD surface contour the drains would be set at 3.0m
AHD (4.0m-1.0m). As the drains would therefore be at or below the water level in the
swales they would be ineffective. Water does not drain uphill.
Figure 13 Photo of drains “swales” on subject land.
The photo above is of a constructed drain on the site. This is effectively the same as
the “swales” proposed in the drainage recommendations. The water is at or near the
surface ground level. The land at this point is between 3.3m to 3.5m AHD (assumed
from comparison with this location and the Flood Study Model), that is, higher than
the proposed swale position of 3.0m AHD. The lagoon was at 1.84m AHD (data
MHL) at the time of the photo. The presence of Water Lilies, which only survive in
standing water, the position of their leaves at the surface and the location of the
37
Melaleucas on the edge of the “swale” all indicated that this would be a typical water
level.
It appears that under the present climatic conditions, and average water levels in
the lagoon, it will be difficult, if not impossible, to effectively drain the subject
land such that it is suitable for urban development. The drainage scheme as
proposed by Douglas Partners alludes to the potential impact from climate
change, by drawing attention to the critical nature of the berm height, but it has
not been addressed in their assessment or recommendations.
4.2.1 Pollution and Drainage
The subject land has two immediate potential sources of pollution. The site has been
identified as potentially having acid sulphate soils, less than a metre below the
surface, in the central section around the creek and surrounding low-lying land (LES
pg 31). It also has a polluted site on its northern boundary, the disused fuel depot,
which has plumes of hydrocarbon polluted water. These plumes, currently, mainly
flow north to the creek.
We believe that if a drainage system were to be installed, which could effectively
drain the subject land and lower the water table, such that it would be suitable for
development, it could potentially be disastrous. Lowering the water table will increase
the drainage gradient between both the acid sulphate soils and the polluted
groundwater. This in turn would draw the pollutants into the drains and potentially
fast track them to the receiving waters, the adjacent wetland.
The studies undertaken in the course of preparing the LES for this site explicitly or
implicitly identify the integral relationship of the proposed development site with
Saltwater Lagoon, the adjacent, listed SEPP 14 wetland. The Hydrogeological
Assessment by Douglas Partners, recognizes the subsurface connections. The Flood
Study, Estuary Management Study and Plan and the Saltwater Lagoon and Creek
Catchment Stormwater Management Strategy carried out by WBM Oceanics,
recognize this connection as the site encompasses a significant proportion of the flood
plain. The vegetation and fauna study identifies the biological links, the land is
recognized as an important wildlife corridor by NPWS.
“The engineered system will never fully replicate the existing natural
processes. Groundwater flows entering the development exclusion zone may
be subject to higher variability than previously, as some water may be fast
tracked to the wetlands/infiltration swales rather than travelling through the
aquifer which offer a high level of storage and therefore moderates
fluctuations in flow.” (Hydrogeological Assessment 2007, pg 29) (our
emphasis)
“The construction of houses and roads will lead to an increase in the
impervious area, and a decrease in infiltration, potentially leading to
increased surface runoff and decreased groundwater flows. This has
implications for the quality of surface runoff and groundwater reaching the
creek and the lagoon.” (Hydrogeological Assessment 2007, pg 27)
38
Swales and wetlands are proposed as a method of detaining and extracting pollution
and nutrients from the site. As it appears that the site may flood more regularly due to
climate change, it could be anticipated that these measures will not cope. This would
mean that nutrients and pollution could be regularly discharged into the receiving
waters, the SEPP 14 Listed wetland.
“Based on the measured nutrient concentrations and extent of algal growth
within the estuary, it is considered that Saltwater Creek and Lagoon system
is already at or exceeding its natural capacity to accept catchment loads.
Further increases in the amount of nutrients and other pollutants
discharged to the system may result in catastrophic changes to estuarine
ecology, which may be very difficult (if not impossible) to reverse. Over-
development of some ICOLL catchments, particularly around Sydney, has
resulted in highly degraded estuarine systems possessing little ecological
value (eg Manly Lagoon, Curl Curl Lagoon, Terrigal Lagoon).”
(EMP 2006 pg 2-10) (our emphasis)
4.2.2 Conclusion
Drainage assumes there is a low point to which water may be drained. When
the lagoon is at an AHD of 1.2m this may be the case. However the lagoon is
often higher than this, and if left to natural processes could often be above
2.0m AHD (2.21m AHD on 16th
Feb 2009), and as the recent storms
demonstrate as much as 3.0m AHD. At the generally higher levels, which are
the norm in this lagoon, we believe the drainage system proposed would be
inadequate at present sea level. Future sea level rise has not been addressed.
The drainage assessment and recommendations only look at the groundwater
in relation to the impact by future development within the proposed
development site, as if it is in isolation from the surrounding landscape. This
is far from the case as the groundwater is continuous, underlying the entire
lower part of the basin. Increased runoff from the expanding paved and
urbanized surrounding catchment has not been addressed. The potential to
draw in polluted groundwater from both the acid sulphate and polluted fuel
depot if the groundwater level is lowered due to drainage could prove
disastrous. The predicted increase in storm events, such as the ones we have
recently experienced, makes it clear that the figures used to model the
proposed impacts and engineering solutions are simply inadequate.
The proposal to install “vertical drains” while being potentially
environmentally destructive will be of little use, given the effect of climate
change will be to generally raise the watertable.
The proposal to develop this land is akin to asking a skin surgeon to separate
Siamese twins, only to find that they share one heart. We can anticipate the
outcome of such an operation.
39
5 Appendix 5: Impact on Threatened Species Located on Site
Several threatened species have been recorded on this site:
“Of the threatened species known to occur in the Kempsey Shire LGA, five
are known to occur in the study area. These are the Wallum Froglet (Crinia
tinula), Squirrel Glider (Petaurus norfolcensis), the Little Bent-wing Bat
(Miniopterus australis), Grey Headed Flying Fox (Pteropus poliocephalus)
and the Common Blossom-bat (Syconycteris australis).” (LES pg 28)
Of the threatened species, the one which would appear to be most significantly
affected by the proposed development is the Wallum Froglet. The proposed
development significantly reduces suitable habitat for the species.
5.1 Wallum Froglet (Crinia tinula)
The Wallum Froglet is listed as “vulnerable” under schedule 2 of the Threatened
Species Conservation Act (TSC Act)
"Clearing of native vegetation" has been listed as a KEY THREATENING
PROCESS on Schedule 3 of the TSC Act.
The Wallum Froglet was located on this site in April 2004.
“During a two day site inspection undertaken for Connell Wagner (2005), the
Wallum Froglet was detected across a large proportion of the study site
following a single rainfall event on 21st April 2004 (Figure 5.1).” (LES
appendix-e pg 9)
5.1.1 Distribution and Abundance on the Study Area
“The Wallum Froglet was located across a large part of the study area, as
shown on Figure 5.2. This calling activity indicated a relatively even
distribution across much of this area. The habitats have been slashed
regularly over a number of years, which has lead to the vegetation being
lower and more open than what might have occurred previously. This
disturbance history is likely to have created habitats that may be more similar
to early successional stages of this species habitat. It is not known what
impact this has had on the abundance of the Wallum Froglet in the study
area.” (LES appendix A of appendix d no pg number)
And the habitat was noted as being “significant habitat:
“Due to the large area of known habitat, the study (sic) is considered likely to
contain significant habitat.” (LES appendix A of appendix d no page
number) (Their emphasis not ours)
40
“The study area, being a relatively low-lying area, contains numerous shallow
depressions, which fill with water shortly after rain. These provide breeding
habitat for a number of frogs, including the Wallum Froglet (Crinia tinnula).”
(LES, appendix “d” Pg 20)
“The term 'Wallum' is commonly used to describe coastal vegetation types
growing on sand dunes or flat to undulating country with acid soils and a high
water table. The Wallum Froglet belongs to a group of frogs known as acid
frogs (Ingram and Corben, 1975), so named for their ability to breed in waters
of low pH (high acidity) which are characteristic of coastal wetlands.” (LES,
appendix “e” Pg 2)
“Areas supporting wallum vegetation, in turn, are known to be favoured by
the Wallum Froglet. Hence, it is reasonable to base the predicted occurrence
of the Wallum Froglet within the study site not only on the vegetation, but
on the underlying soil landscape, particularly as the physico-chemical
nature of water bodies is strongly influenced by the underlying substrate.”
(LES, appendix “e” Pg 5) (our emphasis)
5.1.2 Disturbance and the Wallum Froglet
The “study area” is noted as having been disturbed:
“The disturbance history is likely to have created habitats that may be more
similar to early successional stages of this species habitat.” (LES 5.1
Appendix A, of Appendix d)
and:
“Parts of the study site have been periodically slashed over a number of
years, which has lead to the vegetation being lower and more open than what
might have occurred previously. It is not known what impact this has had on
the abundance of the Wallum Froglet in the study site (Connell Wagner 2005).
However, this species has been recorded in similarly disturbed situations and
thus displays some tolerance to recoverable disturbances such as slashing
(Darkheart 2004; Darkheart 2005; Darkheart 2006). Despite past
disturbance, the habitats on-site are considered capable of sufficiently
recovering and maintaining an extant Wallum Froglet population, providing
other threats (eg vegetation clearing, reduced water quality) are mitigated.”
(LES appendix-e pg 10)
The habitat described is Wetland Heath vegetation. Wetland Heath communities are
naturally subjected to frequent disturbance from flooding, drying and burning. They
have a very high resilience to disturbance. It could be anticipated that if the
disturbance factor were removed this community would quickly recover in structure,
form and species diversity.
“All of the wet heath associations mapped in the study area are recognized as
a regionally vulnerable. The wet heath associations to the west of the
saltwater lagoon have been recently slashed and/or burnt, however they
41
continue to exhibit a reasonably high floristic diversity as such have
potentially high flora and habitat conservation value. Management of this
area should consider the conservation values of the mosaic of wet heat
communities.” (Flora and Fauna Study, Kendall and Kendall Feb 2003,Pg 31).
However in light of the proposed drainage works associated with the proposed
development of this site the following appears to be of significance.
“Wallum habitats are highly susceptible to environmental disturbance. Any
small change in the environment, such as variations in hydrology (water
tables and drainage) or the addition of soil nutrients (via storm water and
general runoff), has the potential to affect the ecology of the wallum habitat
and this has flow-on effects to animals living in the wallum. Altered wallum
habitats cannot support the same diversity of species” (LES appendix-e pg 3)
5.1.3 Threats to the Wallum Froglet related to Development
We quote from the “Detailed Wallum Froglet Study” contained in appendix e of the
LES, pgs 3 & 4
“3.4 Threats
The overall abundance of Wallum Froglet is generally considered to be
declining. This decline has been attributed to a number of threats, including
Key Threatening Processes listed on the TSC Act.
These threats include:
• Vegetation clearance and modification of coastal wetlands
Pressure from coastal urban development and historic agricultural landuse
has led to clearing of native vegetation within, and adjacent to, coastal
wetlands, as well as draining and infilling of wetlands. Both clearing of native
vegetation and wetland modification are listed as Key Threatening Processes
on the TSC Act. Both threatening processes have placed enormous pressure
on the Wallum Froglet (DEC, 2006).
• Inappropriate catchment management
Pressure from coastal landuses (such as urban development and agriculture)
have led to poor catchment management and planning decisions. Consequently,
coastal wetlands have been the focal point for impacts from altered stormwater
regimes and subsequent coastal wetland water quality issues have occurred.
The Wallum Froglet is considered sensitive to poor water quality (DEC, 2006).
• Vehicular collision
In a study on the North Coast of NSW, Goldingay and Taylor (un-published)
found that the Wallum Froglet was particularly sensitive to vehicular collision
road fatalities. This threat is typically enhanced when high volume roads bisect
areas of suitable habitat, essentially creating two habitat isolates and sub-
populations.
• Frequent fire.
A high fire frequency in Wallum Froglet habitat is considered a threat to this
species (DEC, 2006).”
42
Figure 14 Photo shows vigorous regeneration following disturbance
(“resilience”)
Resilience
“resilience” – that is the capacity of a community or species to “bounce
back” after disturbance” (McDonald M. Aug. 1996)
The LES appears to confuse clearance with disturbance when it recommends that
increasing the area to be excluded from development is not justified.
“Option 3 has used the 4.0m AHD contour as the basis for habitat retention.
As can be seen from fig 5.2, the additional area encompassed by Option 3 is
primarily that area which has been previously cleared. It is considered that
the quality of the additional habitat provided by including the Option 3 area
as retained habitat would not result in any significant increase in the quality
of habitats already provided by using Option 1” (Option 1 is to the 3.0m AHD
contour) (LES pg 60)
The LES did not investigate the resilience potential for the subject land, and has
failed in its legal duty to provide adequate information for the Council to form
an opinion on this matter.
Note: The Wallum Froglet was identified across the subject land in April 2004.
Why is the habitat still being disturbed in 2009? Was an EIS carried out to
permit this continued disturbance
43