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3.0 Summary of Stage 1 Technical Studies 3.1 Introduction

This chapter summarises the stage 1 technical studies that have informed this planning process. The technical studies are listed in Table 3.1. In sections 3.2 to 3.8 below, each technical study is described in terms of the following: • purpose • methodology including any assumptions or limitations • results of desktop data and literature review • results of on-site investigations • constraints for future development • conclusions and recommendations.

Table 3-1 List of the technical studies undertaken for Stage 1 of the Project

Study Report name Date Author

Slope analysis and geotechnical assessment

Bahrs Scrub LDA: Slope analysis and geotechnical assessment

May 2010 Coffey Geotechnics

Contaminated land assessment

Bahrs Scrub Local Development Area: Contaminated Land Assessment

July 2010 Lambert & Rehbein

Hydraulic assessment

Bahrs Scrub Local Development Area: Hydraulic Assessment

August 2010 Worley Parsons

Cultural heritage study

Bahrs Scrub: Cultural Heritage Study August 2010 Turnix

Landscape and visual amenity assessment

Bahrs Scrub Local Development Area Plan: Landscape and Visual Amenity Assessment

August 2010 Cardno Splat

Ecological assessment

Bahrs Scrub: Ecological Assessment Technical Report

July 2010 Chenoweth EPLA

Bushfire report Bahrs Scrub: Technical Report Bushfire July 2010 Chenoweth EPLA

Each technical study was required to identify constraints to future development of the site. To assist with identifying a net developable/conservation area for the site, mapping outputs from each technical study were based on the following levels of constraint: • Category 1: No or low constraint to development – may require design response but no

reduction in development yield • Category 2: Moderate constraint to development – reduces development yield and/or

removes land from urban development • Category 3: Significant constraint to development – severely reduces development yield or

removes most, and possibly all, land from urban development. Each technical study explains the specific rationale used to categorise site constraints. Key mapping outputs from the technical studies are provided at the end of sections 3.2 to 3.8 for ease of reference. Section 3.9 below provides concluding comments about the technical studies.

3.2 Slope Analysis and Geotechnical Assessment 3.2.1 Purpose

The slope analysis and geotechnical assessment presents the geology and soil conditions of the site with specific regard to landslip risk and foundation conditions. The assessment also provides a preliminary discussion on flood/overland flow hazards and identifies constraints to development that relate to slope stability and other geotechnical hazards.

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3.2.2 Methodology Coffey Geotechnics carried out a desktop study review of published geological data, topographic maps and aerial photographs for this locality. A walkover survey of the site was also undertaken by an engineering geologist, a geomorphologist and a geotechnical engineer. The survey concentrated on areas of potential constraint e.g. steeper topography, gullies, watercourses and floodways. Publically available topographic maps were supplemented with Coffey Geotechnics’ field records of additional gullies, watercourses and likely overland flood paths. The walkover survey identified areas of ongoing erosion and mass movement e.g. landslip and creep. Geomorphological features and outcrops of soil and rock were recorded and described. Potential flood zones were also recorded. In the assessment, terrain areas have been categorised in terms of development constraints specifically relating to slope stability, and also in terms of engineering geological and geotechnical hazards. Areas observed as susceptible to frequent floods were recorded. Figures showing the spatial distribution of geotechnical constraints categories were included in the assessment.

3.2.3 Desktop Review 3.2.3.1 Published Geology

The site is underlain by Paleaeozoic (Devoian and Carboniferous age) Neranleigh-Fernvale Beds rocks, that are locally obscured with alluvial and colluvial soil. The group of rocks making up the Neranleigh-Fernvale Beds form deeply-dissected topography, characterised by the steep hills and v-shaped valleys that are seen in the Bahrs Scrub area. To the south of Beenleigh, the unit forms part of the Darlington Range that extends south to higher ground at Mount Tamborine in the Gold Coast hinterland. The Neranleigh-Fernvale Beds typically comprises interbedded, folded and sheared greywacke and sandstone, chert with mudstone, shale and occasionally weakly metamorphosed phyllite. Typically sandstone sand and greywacke are the prevalent mapped units in the Beenleigh area. All rock types in the group are locally quartz impregnated and veined, however the quartz content varies. Remnant Triassic age Ipswich Coal Measures Group is present on high ground in the south-western corner of the site. Otherwise the boundary between the Ipswich Coal Measures Group and the Neranleigh-Fernvale Beds is mapped as being beyond the south-western boundary of the site. Geological mapping indicates the presence of intermixed colluvial (slope wash) soils and alluvial deposits along valley sides. These deposits typically comprise cobbles and gravel within clay, and potentially sandy soils. Mapping indicates that colluvium has accumulated within the lower-lying land at the base of relatively steep hillslopes, in the vicinity of Belivah Road. Geological survey mapping indicates the presence of alluvium associated with the Windaroo Creek. Alluvium deposits in the site typically comprises, possibly gravel grading through sand to slit-sized particles and clay. Organic (peaty) soil can also be present.

3.2.3.2 Topographic Maps

Coffey Geotechnics created a digital elevation model from topographic data, using ArcGIS (refer Figure 3.1 below). The site is characterised by an undulating landscape, with ridges cutting across the eastern section of the site. The undulating land typically ranges between 15m and 45m above Australian Height Datum (AHD). Many of the watercourses have been dammed for water supply.


The northern site boundary is marked by an east-west-trending ridge that undulates between some 75m and 95mAHD at its crest. Towards the north-eastern corner of the site there is a distinct, steep-sided, round topped hill (Clarkes Hill) that rises to a height of 145mAHD. Windaroo Creek incises through the hills, forming a narrow valley on the south side of Clarkes Hill. On the south side of the narrow valley, a north-west to south-east trending ridge rises to a height of 205mAHD. Towards the south-west this ridge links to the northernmost part of the Darlington Range. There is an area of low relief and low-lying ground beyond the toe of the ridge at the south-eastern corner of the site. In the westernmost part of the site the topography is a little higher than the central area. Steeper slopes are apparent near the south-western site boundary with the Buccan Conservation Park. A slope steepness map was produced for the site (refer Figure 3.2 below). This map is based on 5m contours and slope is measured in degrees (not percentage). It is clear the steepest parts of the site are those associated with Clarkes Hill and Bahrs Hill.

3.2.3.3 Aerial Photographs

The review of historical aerial photographs assists in understanding the history of development and clearance and, in this instance is helpful to evidence historical landslips. Pairs of adjacent, overlapping photographs were analysed using a stereoscope viewer which enhances depth perception by enabling two views of the same object from a slightly different perspective. The observations did not identify any specific anomalies, but assisted in describing topographic features. Evidence of potentially destructive active geomorphological processes, such as landslips or major erosion, was not apparent in the photographs.

3.2.4 Geological and Geomorphological Observations Much of the landscape was observed as being typical of Neranleigh-Fernvale Beds terrain, being characterised by steep hills and v-shaped valleys, opening to broad and undulating land dissected by small creeks. In areas of higher ground, steep sided and deeply-incised gullies are found where the underlying geology comprises mudstone or siltstone. In contrast, Clarkes Hill has a distinct topography. There are no significant gullies on its south and east flanks and the ground slopes steeply and evenly. In this part of the hill, and at its summit, the rock group is characterised by quartzitic, medium grained and high to very high strength sandstone. This is shown in Photo 3.1 (sourced Coffey Geotechnics, 2010).

Photo 3.1 Quartzitic sandstone at the summit of Clarkes Hill

At the far south-western corner of the site, Bahrs Scrub Road rises onto a ridge. Distinctive conglomerate was observed here on higher elevation ground, exposed in shallow cuttings adjacent to the road. This conglomerate also outcrops within Buccan Conservation Park.


Topsoil and colluvium covers the bedrock throughout the undulating and steep terrain. In areas where runoff has been concentrated, such as adjacent to roads, gully erosion has exposed rock within incised channels typically below 800mm deep. This is shown in Photo 3.2 (source Coffey Geotechnics, 2010). The colluvium comprises clay, sandy clay and gravelly clay, gravel comprising angular and typically platy particles, with some gravel of quartz. No significant boulder or cobbles were noted. Within the steeper sided gullies, there is some evidence of very slow soil creep and some spalling of gravel from exposed colluvium. Slumping and sever gully erosion was observed where land has been cleared on the eastern side of Clarkes Hill. This is likely to be the site of a former quarry. The erosion has occurred in material which was interpreted to comprise in part colluvium and in part quarry spoil. This is shown in Photo 3.3 (source Coffey Geotechnics, 2010).

Photo 3.2 Roadside erosion through cover of Colluvium to expose Neranleigh-Fernvale Beds mudstone ‘flat rock’

Photo 3.3 Gully erosion in quarry spoil above

Creeks and gullies within the site are generally narrow and ephemeral, flowing episodically during storms. The hydrologic regime of Windaroo Creek and its tributaries is likely to be flashy due to low ground permeability. Active river erosion (undercutting along the outer banks of meander bends) was observed adjacent to Park Lane. This is shown in Photo 3.4 (source Coffey Geotechnics, 2010). Other


areas of erosion were observed adjacent to Bahrs Scrub Road within the narrow pass between Clarkes Hill and Bahrs Hill, as well as along the outer banks of meander bends further downstream.

Photo 3.4 Roadside erosion through cover of Colluvium to expose Neranleigh-Fernvale Beds mudstone ‘flat rock’

Throughout the undulating ground within the site many of the small and ephemeral waterways have been dammed to provide domestic/livestock water supply. Some dam surfaces have been concreted. It is noted that a review of dam stability was not part of the assessment.

3.2.5 Constraints to Future Development The rationale for the engineering geology categorisation of the site constraints is explained in Table 3.2.

Table 3-2 Rationale for engineering geology categorisation of constraints

Category Rationale

1 Areas of both low and undulating relief that are not considered to represent significant constraint to urban development, in terms of slope stability. This includes land where slopes range between 5o and 15o.

2 Areas of moderate slopes and difficult access areas e.g. ridgelines, separated by steep sided gullies. This includes land where localised erosion has occurred and slopes range between 15o and 20o. These areas are suitable for development where appropriate engineering and management/maintenance measures can be adopted.

3 Areas of steep slopes in excess of 20o. These areas are characterised by deeply incised v-shaped gullies, indicative of severe erosion and soil erodibility. These areas show evidence of soil creep, but no evidence of deep-seated mass movement (rotational or transitional landslides). The southern circumference of Clarkes Hill is also included in Category 3 due to its steep sloping sides.

Coffey Geotechnics prepared a development constraints map for the site based on this rationale (refer Figure 3.3 below). The development constraints map excludes an indicative flood prone area, which is an observed extent of the current floodplain associated with the main creek channel. If development was proposed in the floodplain areas a detailed flood evaluation would be required. This map shows that the majority of the site is nominated as Category 1 except for the landforms of Clarkes Hill and Bahrs Hill and pockets of land in the western part of the site which are nominated as Category 2 and 3.


Locations of erosion were noted during the assessment e.g. erosion of the outer bank of a meander bend along Windaroo Creek, adjacent to Park land and upstream of Windaroo Road, and along Bahrs Scrub Road where the creek passes between Clarkes Hill and Bahrs Hill. This erosion may represent a future development constraint if permitted to continue, and as such are shown on the development constraints map (refer Figure 3.3 below).

3.2.6 Conclusions and Recommendations The assessment categorised terrain areas in terms of development constraints specifically relating to slope stability, and in terms of engineering geological and geotechnical hazards. Areas observed as susceptible to frequent flood were also recorded. In terms of slope instability some areas of steeply sloping ground were identified where down-cutting erosion and soil creep represents specific constraints to development. Typically no areas of deep seated landslip were identified on the site. Some areas of ongoing river bank erosion were identified. The eastern side of Clarkes Hill appears to have been quarried and severe ongoing erosion was observed. Recommendations for future development of the site are listed in Table 3.3 below.

Table 3-3 Recommendations of the slope analysis and geotechnical assessment

Issue Recommendation

Category 1 areas

Excavations in low relief areas may be unstable where groundwater is present at shallow depth. Areas of undulating ground are likely to provide a suitable foundation for footings, however all footings should extend beneath any cover of distributed ground, topsoil or colluvium.

Category 2 areas

Measures can be taken in critical areas to improve stability e.g. provision and maintenance of drainage and/or vegetation to reduce pore-water pressures in soil, and structures or in situ reinforcement to physically support the soil. In non-critical areas soil creep can generally be accommodated in aspects of future development e.g. soft landscaping. Engineering solutions need to be sought to assist in maintaining stability on the lower slopes of the eastern side of Clarkes Hill where there has been quarrying and the ground has been terraced, because: � quarry spoil and colluvium is subject to ongoing severe erosion in this area � the existing cuttings are only marginally stable and further instability could

trigger major landslide event, which would be an unacceptable risk in this area.

In relation to building footings: � uncontrolled fill or disturbed ground is unsuitable support for building footings � footings must extend to a competent foundation � drainage measures must be adopted to reduce potential for erosion.

Category 3 areas

In areas of significant ongoing soil creep specialist construction may be plausible is some areas however may not be cost-effective. If constructing any buildings in Category 3 areas: � buildings will require specific design measures and local ground assessment

to ensure adequate bearing capacity � footings must be extended to a competent foundation � drainage measures must be adopted to reduce potential for erosion � observe steep slopes (particularly those characterised by outcropping

sandstone) for potential boulder roll/rock fall occurrences requiring remediation.

General Existing erosion ‘problem areas’ require remediation (refer to locations noted in Section 3.2.5 above). The implications of obstructed gullies on the flood and overland flow regimes of the site need further consideration, particularly the obstructed gully on the eastern side of Clarkes Hill.


Figure 3-1 Digital elevation model


Figure 3-2 Slope steepness map


Figure 3-3 Development constraints map - Geology and slope


3.3 Contaminated Land Assessment 3.3.1 Purpose

The purpose of the contaminated land assessment was to identify any contaminating activities which may have occurred, or is occurring on the site. The assessment was also to recommend, where necessary, remediation measures for such activities.

3.3.2 Methodology The assessment was predominantly desktop in nature and involved review of the following data sources specifically relating to the site: • LCC records including flammable and combustible licence details, Environmentally

Relevant Activity (ERA) records, contaminated sites information and GIS mapping overlays

• Department of Environment and Resource Management (DERM) records including the Environmental Management Register/Contaminated Land Register (EMR/CLR), ERA records and GIS mapping overlays

• DERM historical aerial photographs between 1944 and 2002 • interviews with 24 residents familiar with the properties and history of the site • past contamination-related reports pertaining to the site. A number of site inspections were undertaken to identify activities of concern or identify current and past contaminating activities. At this stage of the planning intrusive investigations would only have been warranted if significant contamination was identified (e.g. that has an impact on environmental and/or human health matters). Upon completion of the desktop assessment and site inspections, no significant contaminating activities were identified.

3.3.3 Desktop Review 3.3.3.1 Historical Aerial Photographs

The review of historical aerial photographs can be helpful to evidence contaminating activities. The following key observations were made: • the site has traditionally been used for agricultural uses such as crops and livestock • there was no evidence of military related activities in the 1944 aerial photograph • the Bayer pesticide research facility which operated between 1968 and approximately

2000 is evident on the 1973 aerial photograph, in the south-east corner of the site • residential development became more prevalent across the site in the late 1970s/early

1980s. Overall, potential for contamination was associated with the Bayer pesticide research facility and rural activities e.g. potential cattle dips, fuel and chemical storage, and pesticide/ herbicide spraying of crops.

3.3.3.2 LCC and DERM Records

LCC and DERM records indicate that there are no EMR/CLR sites within the site. The following additional information was provided by LCC in relation to ERAs near to the site. The proximity of these ERAs to the site has implications for the future planning of the site: • a poultry farm is located on Dairy Creek Road, Waterford (Lot 1 RP883581)

approximately 1.6 km west of the site • a poultry farm is located at the corner of Hein Road Laumer Road, Buccan (Lot 5

RP841523) approximately 1.2 km south-west of the site • a sanitary landfill is located at 45 Wuraga Road, Bahrs Scrub (Lot 1 WD4254)

approximately 140 m north of the site • a sanitary landfill is known to exist to the north-west of the site however its location is

unknown at this time • a LCC waste transfer station is located at 15 Wuraga Road, Bahrs Scrub (Lot 1

SP127066) approximately 500 m north of the site.


3.3.3.3 Resident Phone Interviews

Interviews with 24 available residents were conducted by Lambert & Rehbein. These residents confirmed that their properties had historically been used for cattle farmland or crops (e.g. bananas and mangos). These residents were not aware or any past or present contaminating activities such as cattle dips, chemical storage tanks or petroleum storage tanks.

3.3.3.4 Past Reports Pertaining to the Site

A number of contamination-related reports have been prepared for the site, including a Stage 1 and 2 Environmental Site Assessment and Validation report prepared by Lambert & Rehbein (October 2006) at the former Bayer site and a Due Diligence Contamination report prepared by Gilbert & Sutherland (December 2007). The relevant conclusions of these reports are summarised in Table 3.4.

Table 3-4 Summary of past contamination-related reports

Report Description

Stage 1 and 2 Environmental Site Assessment and Validation report Lambert & Rehbein, October 2006

Bayer operated a research facility to evaluate animal health chemicals on Lot 110 WD3112, in the south-east corner of the site, between 1968 and approximately 2000. The facility involved testing of pour-on applications, dipping spraying, oral treatments and injections. Lambert & Rehbein believed there to be three cattle dip tanks immediately north of the facility, used primarily before the facility was constructed. These tanks were later removed. The property has since been remediated in accordance with DERM’s requirements. Based on the findings of these reports it was concluded that the property was then suitable for unrestricted use and should be removed from the EMR.

Due Diligence Contamination report Gilbert & Sutherland, December 2007

Gilbert & Sutherland prepared a due diligence contamination report for Stockland and selected 36 properties within the site. Of the properties assessed, the following conclusions were made: � no properties were listed on the EMR/CLR � no ERAs were identified on the properties � minor potentially contaminating activities were found on-site (e.g.

pump houses, workshops, pool chemical storage and small volumes of petroleum/oil storage) however these were not considered significant constraints to future development.

3.3.4 Description of Potentially Contaminating Activities A number of potential areas of concern were identified during the desktop study and site investigations. These areas were potentially contaminated soil stockpiles, rural properties containing potential contamination sources, waste products and chemicals, and the land quarry. Where possible, follow up interviews were undertaken with residents of the potential areas of concern. Table 3.5 lists the properties which may contain potentially contaminating activities and describes those activities.

Table 3-5 Areas of concern for potential contaminating activities

Property Potential contaminating activities

Lot 11 RP158376 Sheds

Lot 1 RP196325 Workshop

Lot 2 RP196325 Sheds and above ground fuel storage tanks

Lot 33 RP228883 Workshop and above ground fuel storage tanks

Lot 1 RP896191 Sheds and above ground fuel storage tanks


Property Potential contaminating activities

Lot 17 RP121176 Sheds and pump station

Lot 14 RP161279 Potentially contaminating stockpiles (construction rubbish, steel pipes etc near a waterway corridor)

Lot 28 RP169807 Potentially contaminating stockpiles (small amount of fill within a waterway corridor)

Lot 904 SP128618 Quarry (use of heavy machinery and potential fuel storage/ spillage)

Lot 502 SP217549 Stockpiles (potentially residual from the former Bayer facility, but considered low risk as the property was remediated and validated)

Lot 279 W3148 Possible cattle dip area

These premises have since been referred to the Environmental Assessment Branch of Logan City Council for further examination of their compliance with the relevant legislation.

3.3.5 Constraints to Future Development The assessment did not identify any constraints to future development of the site. As such a development constraints map was not produced. However this does not negate the need for detailed contaminated land assessments on a lot-specific basis for future development applications within the site.

3.3.6 Conclusions and Recommendations The assessment did not identify any significant contaminated land issues likely to affect future development of the site. A number of notifiable activities, and activities that may cause limited contamination were identified within the site however these are likely to be contained within the immediate area of the activity. The following recommendations were made: • follow up action is needed to determine the source of the stockpiled soil identified on Lot

14 RP161279, Lot 28 RP169807 and Lot 502 SP217549 • any additional fill identified for the site needs to be considered for follow up actions to

determine its origin and contamination status • the above ground fuel storage tanks identified on Lot 2 RP169325, Lot 33 RP228883 and

Lot 1 RP896191 need to be investigated to accurately assess their volumes and subsequent requirements as notifiable activities

• any planning mechanism developed as part of the plan will need to incorporate a limited contamination assessment for future development applications on lots with a rural or rural residential land use (e.g. a preliminary lot-specific contamination investigation and subsequent more detailed assessments if required, in accordance with DERM’s Draft Guidelines for the Assessment and Management of Contaminated Lands in Queensland, May 1998).

3.4 Hydraulic Assessment 3.4.1 Purpose

The hydraulic assessment presents a comprehensive assessment of flooding and water quality within the site using the latest flood modelling techniques. The assessment includes a broad scale hydrologic, hydraulic and water quality analysis of the contributing catchment and site. The major components of the assessment are: • identification of existing drainage patterns and infrastructure including major overland flow

paths and waterway structures • development of a catchment-wide hydrologic model using the XP-RAFTS modelling

package • construction of a fully integrated 1-dimensional (1D) and 2-dimensional (2D) TUFLOW

hydraulic model to assess issues and constraints within the site catchment


• hydrological and hydraulic model analysis to define flood levels, flow velocities and drainage behaviour in the study area for the 10, 50 and 100 year ARI design flood events

• investigation of existing water quality characteristics by undertaking an analysis of the existing (baseline) water quality regime in the site using the MUSIC Version 3 modelling package

• identification of various constraints with regard to future development in the site and to suggest recommendations in response to the impacts of flooding.

3.4.2 Methodology Using supplied aerial photographs, contour and digital terrain data, a catchment-wide hydrologic model was developed to determine inflow hydrographs using the XP-RAFTS software package. These inflow hydrographs where then used in a 2D hydraulic model which was developed using the TUFLOW modelling package. For the purposes of this study, the modelling boundary was extended past the site boundary and a normal tailwater depth adopted as the downstream tailwater condition. Tailwater conditions caused by flooding in the Albert River were dismissed due to the distance from the site boundary to the confluence of Windaroo Creek and Albert River and the numerous detention structures located downstream of the site. Following the simulation of the 10, 50 and 100 year ARI design events under existing conditions, mapping outputs were developed which highlighted the extent of inundation through the catchment. In order to analyse the existing scenario water quality characteristics in the site a water quality analysis was undertaken using the MUSIC software package. Following the development of the various models, a review of the results was undertaken with a view to developing a series of waterway management strategies for both water quantity and quality. A series of figures showing the extent of inundation, the identification of exclusion zones and potential mitigation areas was also developed following the completion of the modelling tasks. As part of the study, Worley Parsons also undertook a detailed and comprehensive site inspection of the site to assess the physical catchment parameters, verify crossings and existing hydraulic structures, investigate waterway systems understand the flow dynamics of the catchment area and major waterway systems.

3.4.3 Description of Site and Catchment Area The site is defined by large sections of heavily forested areas bisected by tributaries of Windaroo Creek, which discharges into the Albert River. With regards to the site’s catchment area, a large portion of the catchment is vegetated and development exists in a semi-rural state with isolates pockets of low density residential uses. Approximately 57% of the total catchment area has thick vegetation. The eastern and south-eastern areas of the catchment have a greater portion of residential development with one new development currently under construction in the south-eastern corner of the site.

3.4.4 Hydraulic Assessment Due to the steep and undulating topography of the site, flooding is generally confined to the deep channels and gullies throughout the system, with isolated break-outs occurring in areas of low-lying floodplain. Figures 3.1 to 3.6 of the hydraulic assessment display the results for the design event analyses for the existing flooding scenario. Due to the site’s steep gullies and waterways the extent of flooding does not vary considerably between large and small events. This is particularly event in the upper reaches of the waterway system where there is very little distinction between the 10 and 100 year ARI design event storms.


For planning purposes, a stormwater drainage exclusion zone has been defined for the site as land found below the 100 year ARI design flood event (refer Figure 3.4 below). Potential waterway enhancement areas have also been identified for the site (refer Figure 3.5 below). Potential enhancement areas include sections of the floodplain where there is little or no channelisation and the flood extent is poorly defined. Road crossings on Bahrs Scrub Road, Prangley Road, Tarwonga Road and Menora Road within the site presently become inundated during the 10 year ARI event. The majority of these inundations exceeded the Queensland Urban Drainage Manual (QUDM) guidelines for safety. The locations of road inundation are identified on Figure 6.2 of the hydraulic assessment (refer Figure 3.5 below).

3.4.5 Water Quality Assessment The key goal for stormwater management is to ensure a reduction in the level of social and environmental disruption caused by polluted stormwater and flooding. Best practice techniques and structures for stormwater management, suitable for SEQ conditions include source controls, run-off reduction controls, infiltration controls, and pollution interception controls. The preferred approach to stormwater management uses a combination of the above controls at a variety of treatment scales, such as the allotment scale, street/neighbourhood scale, sub-catchment/development scale and catchment/regional scale. The three overarching principles driving the water quality management approach for the site are: 1. A ‘daylight’ approach for stormwater conveyance. By utilising swales to convey flows

rather than concrete pipes and channels, the volume of stormwater flows are reduced, and treatment begins at the source. If properly set out and adopted, this approach will likely result in not only cost savings, but also improved water quality and water health.

2. Upstream flows from undeveloped areas are to be separated from urban stormwater. Separation in this way not only decreases the volumes of water that will be required to be treated but will ensure better outcomes for the natural creeks in Bahrs Scrub.

3. A combination of best management practices in water sensitive urban design (WSUD) at various scales. Stormwater runoff will be treated by a range of treatment devices prior to discharge to the receiving waterways. This approach will implement stormwater treatment measures at three of the four spatial scales mentioned above; allotment, street/neighbourhood, and sub-catchment/development scales.

Table 3.6 summarises the types of water quality treatment devices and the various scales at which they can be adopted for the site. These devices are further explained in Section 6 of the hydraulic assessment.

Table 3-6 Possible stormwater treatment measures and scales for the site

Scale Typical measure employed Justification

Allotment Rainwater tanks Sand filters

Rainwater tanks area a legislative requirement. Sand filters are suitable for small areas and treat stormwater at the source prior to conveyance.

Street Buffer strips Bioretention swales Rain gardens

Encompasses the heart of the ‘at source’ approach, dealing with stormwater quality both where the rain falls, and during conveyance rather than at the ‘end of pipe’.

Neighbourhood Gross pollutant traps Only recommend based on land use e.g. areas which generate high amounts of gross pollutants or areas that have known litter problems (e.g. commercial or industrial areas, near educational institutions).


Scale Typical measure employed Justification

Sub-catchment/ development

Bioretention basins Constructed wetlands

At development-scale, larger bioretention basins and wetlands may be feasible where neighbourhood scale treatment is not practical. Bioretention basins are wetlands are important in removing key stormwater pollutants and provide attenuation of hydrologic peaks.

Logan City Council preference is that the area is developed with 2 to 3 larger sub-catchment facilities, rather than numerous allotment, street and neighbourhood level facilities. The final drainage treatment train for this area will be determined in the next round of technical studies.

3.4.6 Waterway Management Future development of the site will cause an increase of run-off, due to an increase in impervious areas such as concrete from new roads, roofs and driveways. This net increase will need to be addressed during detailed design and construction to ensure no worsening of flows in accordance with LCC guidelines. A waterway management strategy will require a combination of management actions, including enhancement and maintenance of riparian corridors and physical protection against erosion. The approach adopted for the site comprises identifying the key environmental values to determine waterway management strategies to satisfy the following constraints: • protection and conservation of ecological values • risk reduction • water quality improvement (optimal sediment and nutrient attenuation) • flooding extent (10 and 100 year ARI). Stormwater management (quantity and quality) within the site will be based on the ‘desired standards of service’ (DSS) for stormwater management developed by LCC, which is currently being developed. As LCC’s DSS for stormwater management were not available for release at the time of writing the hydraulic assessment, Worley Parsons’ proposed waterway management strategy recommends stream channel management approaches for future development of the site to be consistent with the DSS outlined in Section 8 of the hydraulic assessment. It is generally recommended that the existing waterbodies in the catchment are retained and enhanced rather than new facilities to be constructed. Analysis of the enhanced detention facilities needs to occur during the detailed design phase of development. Further analysis would also need to be undertaken to ensure that ‘wet ponds’ are sustainable and are not likely to dry out during extended dry periods. The plan-making process provides a unique opportunity to incorporate riparian corridors for the site rather than as an afterthought when ‘available space’ becomes the main constraint. This can be achieved by maintaining in-tact remnant vegetation and enhancing riparian corridors in degraded reaches, in order to provide a continuous riparian corridor along waterways within the site. There are no specific guidelines for establishing riparian buffer widths, which will vary depending on the ecological values and other planning considerations. Riparian corridors for the site are proposed to be either the 10 year ARI flood extent or the buffer distance shown in the planning scheme measured from the top of the bank, whichever is greater (refer Figure 7.1 below). Some parts of the existing waterway system also require physical protection and/or rehabilitation to prevent further bank erosion, bed scour and downstream sedimentation. Suitable strategies to address these problems include: • bank or channel re-shaping in areas of severe erosion or bank undercutting, prior to any

revegetation efforts occurring • channel dredging in areas of accumulated sediment • use of natural and biodegradable erosion control mats to facilitate re-establishment of

nature vegetation or provide stability for planted vegetation • upgrade and/or stabilise existing stormwater culverts and incorporate channel/bank

protection (e.g. concrete aprons, rock chutes).


In terms of a water quality strategy for the site, it is preferable that a treatment train be incorporated into the design of any proposed development rather than single treatment devices.

3.4.7 Constraints to Future Development Rather than identifying Category 1, 2 and 3 constraints to future development, it was more appropriate for the hydraulic assessment to identify a stormwater drainage exclusion zone for the site. This exclusion zone is land found below the 100 year ARI design flood event (refer Figure 3.4 below). While recognising the importance of hydraulic constraints for the site, it is also acknowledged that some waterways are of higher integrity or priority than others. The retention of waterways and the possible piping of others will be considered along with the ecological values of the site later in this report (refer section 3.7.5 below).

3.4.8 Conclusions and Recommendations The assessment identified and quantified the extent of inundation in the site catchment for the primary purpose of defining the waterway corridor and identifying developable land within the site. The analysis showed that for the majority of the catchment, the extent of inundation is generally confined to the waterways, however sections of flatter topography cause floodwaters to distribute over large low-lying sections of the floodplain. These sections of the catchment are identified as having potential for the increase of developable, flood immune land via waterway augmentation or the inclusion of large scale detention basins. Inclusion of these enhancements may result in improved conveyance through formalisation of waterway channels or reducing the impact of future development by detaining flows under ultimate development conditions. Numerous road crossings throughout the site are currently inundated during the 10 year ARI event with the majority of these crossings exceeding the QUDM guidelines for safety (refer section 3.4.4 above). In order to establish safe access routes during flooding events, it is recommended that the upgrade of these crossing be investigated. The water quality analysis indicated that the catchment in its existing state is performing to a satisfactory level with regard to water quality treatment. Any future development will have to either maintain or exceed these standards. The results from the hydraulic and water quality analysis were used to develop a series of strategies for the management of the various waterways within the site. Water management strategies for both water quantity and quality are: • identification of a stormwater drainage exclusion zone, based on the 100 year ARI design

event • identification of a riparian corridor, based on the 10 year ARI design event • identification of potential risk areas with regards to road inundation, based on the 10 year

immunity/trafficability • locations where channel/waterway enhancement can be undertaken to increase

conveyance and visual amenity • highlight locations where potential detention of flows can occur, to mitigate an increase in

flow in future catchment development • identification of riparian/conservation area links • management of riparian corridor • potential sites for physical protection/remediation • inclusion of WSUD measures in future developments.


Figure 3-4 Stormwater drainage exclusion zone (Q100)


Figure 3-5 Waterway (Quantity) Management (100 year ARI Flood Depth)


Figure 3-6 Riparian corridor (Q10)


3.5 Cultural Heritage Study 3.5.1 Purpose

The cultural heritage study comprises of five parts which when read consecutively provides a complete assessment of Aboriginal and European cultural heritage for the site. The purpose of the study is to provide: • an introduction and background to Aboriginal and European cultural heritage matters

relevant to the site (desktop reviews) • a preliminary investigative study of Aboriginal and European cultural heritage evidence

remaining at the site (field inspections) • a draft deed of agreement in relation to Aboriginal cultural heritage matters for future

development. The two parts of the study that address Aboriginal cultural heritage will guide the detailed investigations of Aboriginal cultural heritage that may become necessary as development proceeds at the site. A Deed of Agreement has also been prepared for future development which, subject to agreement of all parties, can form the basis of an ongoing cultural heritage agreement between the Traditional Owners and LCC.

3.5.2 Methodology

3.5.2.1 Aboriginal Cultural Heritage

A variety of documentary sources were investigated and analysed to compile the desktop report. This report concentrated on determining the territory, language and name of the Traditional Owners of Bahrs Scrub. Considerable effort was made in researching the traditional economy (plant, animal and technology resources). Field inspections were undertaken by Turnix and a Traditional Owner representative. There was virtually no ground visibility for all areas of the site. Field inspections were undertaken along road reserves, the former quarry area, northern side of Clarkes Hill and properties near Windaroo Creek. The two parts of the study that address Aboriginal cultural heritage have been carried out in accordance with the cultural heritage duty of care provisions of the Aboriginal Cultural Heritage Act 2003. These parts may be regarded as a ‘due diligence’ report.

3.5.2.2 European Cultural Heritage

A variety of historical documents and maps were consulted to compile the desktop report. The report examines some aspects of the history of Bahrs Scrub and its Logan district historical context, however is not intended to provide a full historical context. Field inspections were undertaken by Turnix and an archaeologist. Observations noted during the field inspections for the Aboriginal cultural heritage component of the study were also drawn upon.

3.5.3 Desktop Review


Geology maps for the site and surrounding area indicate that Windaroo Creek may have been a source of suitable fine-grained tool stone rocks derived from Chillingham Volcanics Group, which overlie the Neranleigh-Fernvale Beds. Windaroo Creek drains from the Chillingham Volcanics. Although the smaller tributaries of the creek are unlikely to have been permanently source of water, the lower parts of the creek are expected to have been a permanent water source. Everyday tools could be made from these rocks such as axe-heads and stone cutting tools. It is possible the first European explorers of Bahrs Scrub were timber-getters in search of cedar trees. However as Windaroo Creek was not large enough to allow the rafting of logs, Bahrs


Scrub was not impacted by timber-getting until the 1860s when tracks were created to transport logs by wagon. Therefore, hilly places such as the site became refuge areas for Aborigines under pressure in their former territories. If so, the meagre resources of this refuge site would have been stretched to their limit. In the late 1860s/early 1870s, the large grazing runs across Bahrs Scrub began to be subdivided into freehold lots. However the freehold lots created over the site were noticeably larger than those created on flatter land with better soils and water supply. This was early recognition the site’s terrain was generally unsuitable for cultivation. The subdivision of land at Bahrs Scrub and their purchase by European settlers saw the virtual disappearance of the Traditional Owners of Bahrs Scrub by the late nineteenth century. Consequently there is no trace of direct descendants of the Traditional Owners of Bahrs Scrub. However representatives of Traditional Owners whose ancestors spoke a related language are recognised by DERM as culturally proper caretakers for the area. Very little is known about the Traditional Owners of Bahrs Scrub as it appears they were dispersed or passed away before their existence could be sufficiently recorded. In the absence of a known clan name, the Gugingin (meaning ‘northern people’) has been accepted by other Traditional Owner groups. Their territory ranged from Jimboomba on the Logan River, across the Birnam Ranges to the Albert River, to the coastal estuary areas (refer Map 5, Part 1 of the study). The language spoken by the Gugingin was one of the Yugambeh dialects of Bundjalung. The desktop review compiled an inventory of plants, animals and technologies that would likely have been used in various ways by the Traditional Owners. Based on the ripening or fruiting periods of plant resources the site would have been occupied most intensely during spring and summer. Plant resources were used as food, medicines, poison for hunting animals and indicators of the seasons. A wide range of animal food resources likely exploited by the Gugingin still exist in the Windaroo Creek catchment (e.g. fresh-water fish, birds, lizards, snakes). The Gugingin would have used elements obtained from plants, animals and inorganic materials to construct string, fishing lines, nets, bags, baskets, resins and tools and implements. The site is considered to have limited economic resources so the Gugingin would have used the site only seasonally when sufficient resources had accumulated. Fire was used for cooking, heating and land management. The widely used land management technique of ‘firestick farming’ effectively regulated important plant, animal or technical resources. This land management technique would have been used by the Gugingin across the Bahrs Scrub area. Very little is known of the social organisation of the Gugingin. Notwithstanding this, knowledge of neighbouring groups may allow a number of cultural features to be established for the Gugingin. This includes: marriage amongst groups with related languages; existence of smaller family groups covering multiple territories within a broad territory that belonged to an extended family group; and the coordination of smaller family groups for a large hunting event. The kinds of Aboriginal places that may have been encountered at the site include occupation sites, quarries, fish traps, ceremonial grounds, scarred trees and significant stands of plant food resources. It is possible that the terrain of the site, which is unfavourable to farming, has actually served to protect some kinds of cultural evidence that might have otherwise disappeared. A major occupation site was found at the Albert River end of Bannockburn Road (west of the site) however no such places were found within the site.


The Bahrs Scrub area was passed by the early graziers and timber-getters during the 1840s and 1850s because the land was unsuitable for their purposes. From the 1860s onwards, pressure for farming properties increased and the fertile low-lying land skirting the site was progressively ‘taken up’ and subdivided. Farming was the most common historical use of land in the Logan area. Prominent among the smaller farmers were immigrants from Germany. However the site was a difficult area to farm and remained as a sparsely populated rural retreat. The site was eventually subdivided into lots


of a size more suitable to beef cattle or dairying. Some parts of the site remained unallocated even in 1927. A series of survey plans which show the progressive subdivision of the site between 1876 and 1941 are provided in Part 4 of the study. As the population south of Logan grew, a network of roads and tracks became established. Some of the winding roads within the site may still follow the original tracks. It is possible that roads such as Wuraga Road along the sites northern ridge followed earlier Aboriginal pathways as well as being a timber haul road. A GCCC map (2004) showing historical landscape elements of the locality identifies a coach route traversing the site. However considering the topography of the area the mapped route between Waterford and Belivah seems highly impractical. A more probable route would have traversed the site using Prangley Road in the north, Bahrs Scrub Road and Beaudesert-Beenleigh Road to travel further south. In the 1960s the (then) Albert Shire permitted the subdivision of the earlier farms into 10 acre (4 hectares) lots. This saw the establishment of small ‘hobby farms’ across the site. Presently the site remains as a semi-rural community. An Energex transmission line bisects the site in a south-western to north-eastern direction. A review of historical documents indicates conflicting information regarding the naming of the prominent Clarkes Hill within the site. Clarkes Hill is also described as Mt Albert and Mt Waldron in historical documents dated 1866.

3.5.4 Description of Existing Cultural Heritage Values 3.5.4.1 Aboriginal Cultural Heritage

Field inspections did not reveal evidence of any Aboriginal cultural heritage places. The site may have provided suitable rock for everyday cutting and scraping tools to its inhabitants, but it is unlikely to have supplied rock for such to the wider area. Most occupation evidence that is likely to be found at the site will be located within about 100m of a semi-permanent or permanent water source. The ridges may have been used as pathways to travel across the site. Because Bahrs Scrub was a refuge area during the initial occupation of the Logan and Albert district by graziers and timber-getters (approximately 1840s to 1860s) the inhabitants may have left behind relics suggestive of contact with Europeans. Items such as steel axes and wedges, knives, crockery and glass may be expected to be found at the site.


No significant landscape features, beyond those already identified in the desktop review, were recorded during the field inspection. The site currently reflects a semi-rural character. During the field inspection a number of dwellings within the site were noted as potentially possessing cultural heritage values. These dwellings are located at 108 Prangley Road, ‘Fiddlewood’ at 7 Majella Crescent, 31 Bahrs Scrub Road, 65 Bahrs Scrub Road and 31 Belivah Road, as shown on Map 6, Part 5 of the study. These dwellings are not currently listed on any heritage registers.

3.5.5 Constraints to Future Development


The assessment did not identify any Aboriginal cultural heritage constraints to future development of the site. As such a development constraints map was not produced. However this does not negate the need for detailed cultural heritage assessments on a lot-specific basis for future development applications within the site.



The assessment identified one European cultural heritage constraint to future development. The rationale for the European cultural heritage categorisation of the site constraints is explained in Table 3.7.

Table 3-7 Rationale for European cultural heritage categorisation of constraints

Category Rationale

1 Sites of lesser significance that may require lesser mitigation processes.

2 Sites of medium significance that may require extensive mitigation processes.

3 Highly significant site that should be preserved in situ.

Parsons Brinckerhoff, on behalf of Turnix, prepared a development constraints map for the site based on this rationale (refer Figure 3.7 below). The single Category 1 constraint identified is that of the historical coach route which likely traversed the site (Prangley Road/Bahrs Scrub Road route).

3.5.6 Conclusions and Recommendations


The desktop review and field inspections identified the following for the site: • The Gugingin are the Traditional Owners of Bahrs Scrub which encompasses the site • the territory occupied by the Gugingin appears to range from about Jimboomba on the

Logan River, across the Birnam Ranges to the Albert River, and then to the coastal estuary areas (refer Map 5, Part 1 of the study)

• no Aboriginal cultural heritage places are presently recorded for the site, and the field inspections undertaken for this study did not identify any such places

• the site appears to have possessed relatively meagre and dispersed economic resources and therefore it is unlikely that any part of the Gugingin lived at the site on a permanent basis

• while the flat parts of the site were kept open and grassy through ‘firestick farming’ management practices, light fire control in the hill country has contributed to the vegetation diversity still apparent today, particularly on the higher parts of the site.

The assessment recommended the following: • an Aboriginal cultural heritage assessment on a lot-specific basis be undertaken for future

development applications within the site • where development is proposed near ridges, the ridges should be inspected for traces of

Aboriginal pathways • where development requires removal or disturbance of topsoil to a depth of 30cm or to

the subsoil (whichever is the greater) an Aboriginal cultural heritage field assessment be undertaken by a Traditional Owner group supported by a Technical Advisor

• future contracting staff undergo a cultural heritage induction before undertaking works on the site.


The assessment indicated that much of the Bahrs Scrub area was agriculturally unproductive except for flatter areas around Belivah Creek. The rapid acceptance of subdivision into 10-25 acre (or 4-10 hectare) blocks in the 1960s and 1970s clearly supports this conclusion. In terms of European occupation, the historical study indicates that the site contains some heritage structures and infrastructure. Consideration should be given to preserving at least some structures in situ and to retaining elements of the early road pattern. Specific conservation recommendations included: • the Prangley Road/Bahrs Scrub route should be preserved as the route dates from the

1860s and was likely used as a coach route


• the dwelling at 31 Belivah Road may meet National Trust property criteria and should be considered for conservation or possible re-use in future development, subject to structural soundness and willingness of the landowner

• the dwelling ‘Fiddlewood’ at 7 Majella Crescent should also be considered for heritage registration, subject to willingness of the landowner.

Figure 3-7 Development constraints map - Cultural heritage matters


3.6 Landscape and Visual Amenity Assessment 3.6.1 Purpose

The aim of the landscape and visual amenity assessment was to provide a detailed analysis of the landscape character and visual amenity values of the site and to outline relevant management requirements that may apply to the site’s future development.

3.6.2 Methodology The analysis of landscape character and visual amenity was based on a combination of on-site assessment, desktop analysis and GIS analysis. On-site assessment took into account existing roads and external viewpoints and places where access to private land is available. The desktop analysis of aerial photography and GIS data assisted with the process of determining the visual catchment of the site, which allowed for an efficient and effective use of time for site visits, by focussing inspections on viewpoints internal and external to the site. On-site assessment of viewpoint positions and site photos were recorded by GPS and digital camera. The photographs are used to express the character of the site and recording impacts of the key site features at both a regional and local landscape scale, which may require protection and management over time. The previous SEQ Regional Plan 2005-2026 ‘Implementation Guideline No. 8 Identifying and Protecting Scenic Amenity Values’ outlined a common method and assessment criteria for assessing scenic amenity and describes acceptable solutions for maintaining and managing these values. The SEQ Regional Plan (2005) describes this as a method that can be used. Due to time constraints Cardno Splat developed an alternative scenic amenity methodology, following procedures outlined in Implementation Guideline No. 8 to verify scenic amenity ratings. This methodology was accepted by LCC.

3.6.3 Description of Existing Landscape and Visual Amenity Values At the regional level, the site is located at the foothills of the Darlington Range and is visually prominent in the flat coastal plain. The topography of the site can be described as a gently undulating river valley surrounded by moderate to steep ridges and associated hill landform on all sides. This is shown on Figure 11 of the landscape and visual amenity assessment (refer Figure 3.9 below). Section 3.3.2.3 above has provided a detailed description and map of the site terrain. The cross section shown in Figure 3.8 below (source Cardno Splat, 2010) depicts the relationship between three significant landscape features within the site – Clarkes Hill, Bahrs Hill and Windaroo Creek. These natural landmarks are recognisable elements of the landscape and assist with site orientation.

Figure 3-8 Section A-A north-south through the eastern part of site Many of the rural residential properties within the site are discrete in the landscape, retain large areas of existing vegetation and are flanked by landforms. The eastern part of the site features traditional urban subdivision character, developed in the 1990s with lot sizes around 800m2. Scars on the landscape are evident in the eastern part of the site, on the mid slopes of Clarkes Hill. This is due to clearing of bushland for a new development area.


3.6.4 Scenic Amenity Analysis Using the scenic amenity methodology, more locally relevant, accurate scenic amenity mapping of the site has been created based on updated GIS data and aerial photography. Scenic amenity mapping for the site indicated the following: • Clarkes Hill, Bahrs Hill, part of the northern ridge and western ridge are regionally

significant elements of the landscape • the upper slopes of the catchment are locally important elements of the landscape • the centre of the site has a medium to low scenic amenity value as this part of the site is

encapsulated by the surrounding ridges and not visible from external viewpoints • the eastern side of Clarkes Hill has a low scenic amenity value due to scarring of the

landscape. This is evident on Figure 39 of the landscape and visual amenity assessment (refer Figure 3.10 below).

3.6.5 Landscape Units Based on the results of the analysis four broad landscape units have been mapped in order to provide a reference for management strategies over parts of the site: 1. Prominent vegetated peaks 2. Prominent ridges and mid slopes with semi-intact vegetation 3. Creek flats and land flats 4. Creek lines, dams and associated buffers. In addition to these landscape units, several major and minor gateways are formed by the combination of existing site features. These gateways are clear from existing road access points and shown on Figure 55 of the landscape and visual amenity assessment (refer Figure 3.11 below). The features that contribute to site character include Windaroo Creek and its tributaries, meandering through the river valley flats, remnant natural stands of vegetation and elevated, forested ridgelines such as Wuraga Road ridge, the western ridge and hilly landmarks of Clarkes Hill and Bahrs Hill. Natural gateways are formed as existing roads enter and pass through scenic parts of the site and are exposed to these natural features. The major gateway is formed on the eastern entry to the site and minor gateways are formed at road entries and junctions along the northern ridges, from Beaudesert-Beenleigh Road south-east of the site and at internal road crossings of Windaroo Creek. Protection of vegetation cover and possible reinforcement of these gateways in future development will ensure the unique qualities of this place are preserved. The elevated terrain around the perimeter of the site has both regionally significant and locally important scenic amenity values. The protection of vegetation cover and minimising construction impacts in Landscape Units 1 and 2 can ensure a green-break is formed around the perimeter of the site.

3.6.6 Constraints to Future Development The assessment concludes that there is a need to protect scenic amenity and landscape values as part of any future development of the site. The rationale for the categorisation of the site constraints is explained in Table 3.8.


Table 3-8 Rationale for landscape and visual amenity categorisation of constraints

Category Rationale

1 Land that has the following: � slopes less than 16% � not so visually prominent (e.g. river valley flats can visually absorb smaller lot

sizes and higher densities � medium to low scenic amenity mapping value � tributaries to the creek system may be Category 1 or 2 and may require a

15m buffer (dependent on ecological values).

2 Land that has the following: � slopes between 16% and 20% may require changes in density and built form � as land becomes more elevated into mid slopes, visual exposure and

vegetation cover increases � locally important scenic amenity mapping value � creek lines and associated buffers may be Category 2 or 3 and impact on the

development footprint (dependent on ecological values) � creek buffer width may be 15-30m each side (dependent on ecological

values).

3 Land that has the following: � slopes greater than 20% � visually prominent elevated land with existing intact vegetation, and not

desirable for high density development � regionally significant scenic amenity mapping value � creek lines and existing dams may impact on development footprint � creek lines and associated buffers may be Category 2 or 3 and impact on the

development footprint (dependent on ecological values) � creek buffer width 30m each side (dependent on ecological values).

Cardno Splat prepared a development constraints map for the site based on this rationale (refer Figure 57 below). This map correlates with the terrain maps already presented in this report in that the constraint categories are highest around the perimeter of the site and lessen towards the low-lying centre of the site. Category 1 areas are found in the river valley area, Category 2 areas graduate up towards the mid slopes and Category 3 areas are found along the major ridges and prominent hills.

3.6.7 Conclusions and Recommendations Using a methodology which has been accepted by LCC, the landscape character and visual amenity values for the site were identified. The assessment sets out detailed management recommendations for each of the landscape units identified for the site. The key recommendations are listed in Table 3.9 below. However Section 7 of the landscape and visual amenity assessment should be consulted for future information.

Table 3-9 Recommendations of the landscape and visual amenity assessment

Landscape unit Recommendation

Prominent vegetated peaks

� Protect local landmarks by restricting future development around the base of Bahrs Hill and Clarkes Hill

� Graduate future lot sizes outwards from the centre of the site, such that larger lots adjoin the mid slopes and ridges around the perimeter of the site

� Retain stands of vegetation where possible, particularly along ridges and in any potential future public open space areas

� Undertake restoration of degraded vegetation on Bahrs Hill and Clarkes Hill where possible

Prominent ridges � Retain stands of vegetation where possible, particularly along ridges


Landscape unit Recommendation

and mid slopes with semi-intact vegetation

and in any potential future public open space areas � No additional development is to occur on ridge-tops (except for well

designed and integrated roadways) � Set designated building envelopes, minimum buffer widths and

development heights below ridgelines � Ensure landscaping strategies incorporate screening and integration

outcomes

Creek flats and land flats


� Undertake restoration work within future open space areas � Additional tree planting and landscaping treatments associated with

infrastructure and roads may assist in framing gateways, screening and softening built form and providing shade and shelter

� Set appropriate building setbacks and height limits (e.g. 2 storeys) where new development adjoins rural residential areas

� Structures, embellishments, signage etc needs to be sensitive to their setting

� Road designs may consider wide grass verges with no kerb and channel

Creek lines, dams and associated buffers


� Undertake restoration work within future open space areas � Identify and rate watercourse values to ensure primary ecological

corridors are preserved and enhanced � Establish suitable buffers 15-30m along key waterway corridors with

wider buffers as required to improve amenity values � Consider fauna friendly crossings where waterways intersect with roads � Explore opportunities to use existing dams for future stormwater

management solutions

Figure 3-9 Landscape character - Landform districts


Figure 3-10 Scenic amenity

Figure 3-11 Landscape units


Figure 3-12 Development constraints map - Landscape and visual amenity


3.7 Ecological Assessment 3.7.1 Purpose

The aim of the ecological assessment was to accurately map the ecological values of the site to assist in developing an open space/conservation network that is appropriate for the site. The assessment focused on: • waterways – location, stream order, catchment area, ecological value to aquatic and

semi-aquatic fauna and appropriate protective buffers • wetlands – location, ecological value to aquatic and semi-aquatic fauna and appropriate

protective buffers • vegetation – mapping of remnant and regrowth vegetation at a scale of 1:10,000, with

emphasis on both remnant and regrowth vine forest communities, provision of recommendations regarding the protection of remnant, regrowth and other significant vegetation communities

• endangered, vulnerable, rare and locally endemic flora and fauna species – survey to locate significant species and identify how the habitat requirements of these species will be accommodated, recommend what additional work is necessary at the detailed site planning stage to locate all significant species and the mechanisms necessary to protect their habitat requirements

• koalas – detailed assessment of representative areas of woody vegetation to ascertain its habitat value to koalas

• local, district and regional ecological corridors plus habitat mosaics – assessment of the species that are currently utilising and moving across the site, as well as recommendations relating to corridor retention, restoration and integration of barrier mitigation measures for infrastructure

• integration of flood affected areas, waterways, wetlands and overland flow areas into the conservation network

• ecotone considerations within and adjacent to the site • areas requiring restoration and rehabilitation • vegetation/biodiversity/habitat offset opportunities • interrogation of Commonwealth, State and local environmental datasets and mapping.

3.7.2 Methodology The methodology used for the assessment is explained in detail in Sections 4 and 5 of the ecological assessment. Broadly the methodology used for the assessment was: • review of Commonwealth, State and local environmental ordinances relevant to the site • review of existing environmental studies and databases, including flora and fauna species

database searches, Regional Ecosystem (RE) mapping, regrowth mapping, biodiversity planning significance mapping, and other literature such as locally-relevant studies

• consultation with State and local government and persons/bodies with experience and local knowledge of the site

• for the flora assessment – consideration of vegetation mapping and land zones (REs), use of reference sites, review of aerial photographs, field survey, and determination of remnant status and threatened species and floristics

• for the fauna assessment – fauna survey (including diurnal/nocturnal bird survey, ground searches, Elliott and cage trapping, pitfall trapping, hair funnels, spotlighting, Anabat bat detection and call playback technique) and assessment of habitats particularly koala habitat

• for aquatic habitat – waterway assessments, GIS mapping exercise to rank the values of waterways (stream order) and on-ground verification of GIS mapping.

Mapping was produced to capture all aspects of the ecological assessment. Key maps are included at the end of this sub-section for each of reference. .

3.7.3 Flora Most REs mapped on the site by the State were identified as being correct. However the assessment also identified the presence of an additional RE in the south-western portion of the


site where there is a change in geology to course grained sedimentary rocks. The REs mapped for the site are listed in Table 3.10 below (source CEPLA, 2010a)

Table 3-10 Regional ecosystems mapped at the site

Regional Ecosystem

Current conservation status under the Vegetation Management Act 1999

Short description

12.3.1 Endangered Galley rainforest (notophyll vine forest) on alluvial plains

12.3.7 Least concern Eucalyptus tereticornis, Melaleuca viminalis, Casuarina cunninghamian fringing forest

12.3.11 Of concern E. tereticornis, Eucalyptus siderophloria, Corymbia intermedia open forest on alluvial plains near coast

12.9 /10.19a Least concern Eucalyptus fibrosa subsp. fibrosa open forest on sedimentary rocks

12.11.3a Least concern E. Siderophloria, E. propinqua open forest on metamorphics +/- interbedded volcanics

12.11.5a, e, k Least concern Corymbia citriodora, E. Siderophloria, E. major open forest on metamorphics +/- interbedded volcanics

12.11.19 Of concern E. tereticornis open forest on metamorphics +/- interbedded volcanics. Usually higher altitudes.

12.11.10 Least concern Notophyll vine forest +/- Araucaria cunninghamii on metamorphics +/- interbedded volcanics

12.11.18 Least concern Eucalyptus moluccana open forest on metamorphics +/- interbedded volcanics

Figure 9 of the ecological assessment (refer Figure 3.13 below) shows the mapped remnant vegetation and vegetation status as ground-truthed by Chenoweth EPLA. Although some areas are mapped as remnant (due to height and cover thresholds of canopy) not all areas supported an integral sub-canopy, shrub layer or ground layer. On many 2-5 hectare lots, lower strata are actively managed by slashing or grazing. Remnant areas of good integrity include large patches of vine forest around Bahrs Hill and large expanses of eucalypt forests associated with Clarkes Hill extending through to Wuraga Road. Only one endangered RE has been mapped for the site, being RE 12.3.1 ‘Gallery rainforest (notophyll vine forest) on alluvial plains’ aligning a section of Windaroo Creek (refer Figure 3.13 below). The RE has been significantly disturbed partly due to the impacts of urban settlement and to the historical severing of the community by Bahrs Scrub Road. A full flora list for the site is provided in Appendix G of the ecological assessment. This list incorporates data from previous studies and new records from this study. In terms of species of Commonwealth and State significance within the Bahrs Scrub area (recorded and likely to occur) previous assessment recorded twelve scheduled species, nine of which were within the vine forest communities. During the field survey, the presence of four of these species were confirmed; Fontainea venosa (Veiny Fontainea), Macadamia integrifolia (Macadamia), Pouteria eerwah (Red Coondoo) and Marsdenia coronata (Forest Milk Vine). Although all nine previously recorded vine forest species were not recorded during the field survey, the site’s vine forest area provide habitat requirements for these species. There is a possibility of other species being present on the site. During the field survey it was identified that potential habitat exists for a number of other species (refer Table 18 of ecological assessment).


3.7.4 Fauna The presence of mammals, bats, birds, amphibians and reptiles have been recorded on the site. A full fauna list for the site is provided in Appendix I of the ecological assessment. This list incorporates data from previous studies and new records from this study. The field survey recorded three species of Commonwealth and State significance within the site (recorded and likely to occur); Phascolarctos cinereus (Koala), Ardea ibis (Cattle Egret) and Merops ornatus (Rainbow Bee-eater). Of particular note, the locations of Koala sightings as they relate to koala habitat mapping are shown on Figure 13 of the ecological assessment (refer Figure 3.14 below). The koala habitat mapping in Figure 13 is based on the State mapping however amendments have been made to reflect on-ground findings (e.g. bushland habitat values were increased when evidence of koalas were found). High value koala habitat is provided on the site in the north-east (much of Clarkes Hill) as well as in the south-east and north-west corners of the site. Chenoweth EPLA have also identified areas of high koala habitat value in the remaining parts of Clarkes Hill and land trending towards the north-west corner of the site (along the Wuraga Road ridge). This category is not a State mapping category but rather a category used for the purposes of this study. In addition to the significant fauna species recorded on the site, database search results indicate that numerous species of birds, mammals and reptiles have a high potential to occur within the site, as vegetation in the site meets the habitat requirements for the species (refer Table 20 of ecological assessment). Based on the specific habitat values identified by Chenoweth EPLA, an overall habitat values map was developed for the site (refer Figure 3.15 below). This was undertaken using GIS resources. Habitat values of very high, high, moderate, low and very low were initially assigned to the vegetation polygons depending on the remnant status of each polygon, which was then refined by field assessments where access was provided. Figure 14 shows that areas of highest habitat value correspond with larger remnants, particularly that area around Clarkes Hill. Much of the vegetation in the western part of the site also supports very high habitat value. Lower habitat values featured regrowth vegetation as well as disturbed or degraded remnant vegetation. Very low value habitats correspond with cleared, open areas that provide limited habitat to fauna.

3.7.5 Waterways and Wetlands Aquatic features of the site include permanent and ephemeral watercourses and constructed dams. State wetland communities mapping shows that the wetland communities correspond with REs 12.3.11 and 12.3.1 along Windaroo Creek (refer Figure 8 of ecological assessment). Chenoweth EPLA ranked the waterways across the site according to their aquatic habitat values. The resulting mapping is shown in Figure 15 of the ecological assessment (refer Figure 3.16 below). It is clear that the highest habitat value stream in the site is Windaroo Creek. Tributaries of the creek, particularly those to the north of the creek are second habitat value streams. Smaller lower order waterways and dams in the site were generally of lower habitat value due to a lack of aquatic resources and/or not being located within remnant vegetation.

3.7.6 Corridors The study area is already mapped within two recognised regional corridor networks, being the: Regional Terrestrial Corridor; and the Border Ranges Corridor. The assessment considers the role of this site as an important component of that broader corridor network and consideration must be given towards retaining the role of the study area as an integral component of a regional linkage. Essentially all vegetation (remnant, non-remnant, scattered trees) facilitates the movement of fauna between broader habitat areas. Fauna movement can be limited by the integrity of vegetation and existence of barriers such as fences, roads and urban development. The principles of conservation biology and landscape ecology indicate that broad corridor bands of interconnected habitat are required to allow regional scale movement for a diversity of


wildlife. This allows connectivity over a longer period of time for entire population or sub-populations and support viable communities of species within the corridor itself. However, the retention of functional ecological corridors in a fragmented landscape is a considerable challenge. It is unlikely that a continuous band of 500m wide habitat can be achieved in an urbanised setting. Therefore the following principles need consideration in this instance: • recognising the current and future value of cleared areas for establishing corridors • recognising the potential value of isolated patches or ‘stepping stones’ • recognising the value of rehabilitation in beneficial locations. Chenoweth EPLA has developed a conceptual corridor network for the site, as shown on Figure 16 of the ecological assessment (refer Figure 3.17 below). The corridor network represents a series of habitat areas defined by Chenoweth EPLA as ‘critical habitat areas’ and ‘important habitat areas’ that are connected by ‘habitat links’. A detailed description of the definitions of these habitat areas and habitat links is provided in Section 9.3 of the ecological assessment. ‘Critical habitat areas’ were selected based on remnant vegetation, highest value koala habitat locations and recorded rare and threatened flora species. These areas are associated with Clarkes Hill and Bahrs Hill and recommended as being excluded from future development. While smaller and supporting less biodiversity than critical habitat areas, ‘important habitat areas’ are considered important for retention and considered management within the site. These areas, and a surrounding 50m buffer, should be retained and managed for the primary purpose of conservation and reducing the intrusion of edge effects. District and local ‘habitat links’ facilitate the movement of fauna between critical, important habitat areas and also connect with vegetation and waterways outside the study area. District links should, ideally, be wide enough to be ecologically functional. Ideally district links should be continuous and at least 250 metres wide in order to retain the full suite of bird species as well as the known and expected range of mammals, reptiles and amphibians present. Local habitat links should form a continuous link that allows passage for a range of fauna and may be opportunistic formed by being co-located within other constraints. These areas have been identified as primary locations for restoration/rehabilitation opportunities.

3.7.7 Buffers Buffering waterways ensures the protection of waterways within the site as well as downstream water quality and aquatic habitat values. The assessment recommends the following waterway buffers be adopted for future development of the site: • 100-200 m for wetlands • 50 m for waterways in upper forested areas • 15-30 m for waterways in the main channel and floodplain tributaries present within rural/

rural residential areas • 10 m for dams • 50-200 m for significant vegetation. This is shown on Figure 17 of the ecological assessment.

3.7.8 Environmental Offset Opportunities Although the site is not currently subject to a local government environmental offset policy, the assessment recommends that where conflicts with environmental values occur offsets should be considered. This would be a way of consolidating the site’s fragmented habitat network. The assessment identifies the following considerations for offsets for the site: • offsets should be located in non-remnant areas within critical habitat areas, important

habitat areas and habitat links mapped on Figure 16 • where appropriate, consider an alternative approach to the ‘like for like’ approach (e.g.

there may be greater ecological benefits in restoring one species or community with another kind)

• offsets need to be based on a sound ecological basis


• the principle of net gain must be considered. The assessment recommends that an environmental offsets policy be developed for the site as part of planning for this area.

3.7.9 Constraints to Future Development The assessment concludes that there is a need to protect ecological values as part of any future development of the site. The rationale for the categorisation of the site constraints is explained in Table 3.11.

Table 3-11 Rationale for ecological categorisation of constraints

Category Rationale

1 � All cleared and ‘sparse’ non-remnant vegetation outside of Critical Habitat Areas and Important Habitat Areas.

2 � All remnant and regrowth vegetation outside of Critical Habitat Areas and Important Habitat Areas (excluding ‘of concern’ and ‘endangered’ REs).

� All Important Habitat Areas. � ‘Very high’ habitat value with one (1) or no flora/fauna species listed as

significant under Commonwealth and/or State legislation.

3 � All Critical Habitat Areas. � All ‘endangered’ and ‘of concern’ REs in the site. � All remnant RE 12.11.10 and portions of advanced, non-remnant 12.11.10. � Ecotonal areas which include RE 12.11.9 and RE 12.3.11. � Known habitat for Marsdenia coronata (Forest Milk Vine). � ‘Very high’ habitat value with two (2) or more flora/fauna species listed as

significant under Commonwealth and/or State legislation.

Chenoweth EPLA prepared a development constraints map for the site based on this rationale (refer Figure 3.18 below). The most prominent constraints category is Category 3 which identifies the areas around Clarkes Hill and Bahrs Hill and along Windaroo Creek as unsuitable for future development. The remainder of the site is categorised as Category 1 and 2 areas, with a greater emphasis of Category 2 areas in the north-western part of the site. Although this map incorporates habitat links as constraints, these links are conceptually located and are not intended to be applied at the property level, or to specific vegetation polygons.

3.7.10 Conclusions and Recommendations The assessment found that large portions of the site support vegetation of State significance that provides habitat for fauna and flora species listed as significant at the Commonwealth and State level. Analysis and mapping undertaken by Chenoweth EPLA has been used to determine the overall ecological values for the site, of which are shown on Figure 18 (refer Figure 3.18 below). Figure 18 clearly shows that the Category 3 areas around Clarkes Hill and Bahrs Hill and along Windaroo Creek are to be excluded from future development. The remaining Category 1 and 2 areas and indicative habitat links provide a guide for locating future development and conservation areas across the site. The assessment recommended that the following work be undertaken at a property level to further ascertain site values for flora and fauna: • seasonal surveys to include the potential presence of migratory fauna species and

account for flora species dormant during certain time of the year • fauna surveys undertaken in different weather conditions, particularly during wet weather

as the study was undertaken during hot and dry conditions • smaller or staged survey areas to obtain a greater understanding of site flora and fauna

values as the study was undertaken over a large area within a short timeframe, and consequently large portions of the site could not be intensively surveyed.


Figure 3-13 Remnant vegetation and vegetation status (CEPLA ground truthed)


Figure 3-14 Koala habitat values


Figure 3-15 Overall habitat values map


Figure 3-16 Waterways aquatic habitat values


Figure 3-17 Conceptual corridor network


Figure 3-18 Development constraints map - Ecological


3.8 Bushfire report 3.8.1 Purpose

The bushfire report was prepared specifically to address bushfire hazard issues relating to the site. The bushfire report: • undertakes a risk and hazard assessment in order to identify bushfire prone land and

level of associated risk • makes recommendations that mitigate the adverse impacts of bushfire to life, property

and the environment, appropriate to future developments and sub-division design in bushfire prone areas.

3.8.2 Methodology The bushfire report was prepared using a combination of quantitative and qualitative assessment and field verification. The quantitative assessment involved conducting a desktop assessment using LCC’s GIS mapping, aerial photography and review of previous studies to analyse the site and surrounds. Vegetation community, slope and aspect were given a numerical value or ‘hazard score’ to determine the level of risk and bushfire hazard severity classification. The combined hazard score rating was used to determine if the site presents a low, medium or high bushfire hazard severity classification. The qualitative assessment involved consulting with relevant government bodies to obtain information on known bushfire events in proximity to the site. A site investigation was carried out by a bushfire management planner and senior ecologist in order to ground truth and verify the findings of the quantitative assessment. Bushfire hazard mapping was finalised by combining hazard scores from the quantitative and qualitative assessments. Bushfire hazard levels (high, medium and low) were ranked by totalling the hazard scores for vegetation community, slope and aspect.

3.8.3 Fire ecology In Australia there are a number of ecosystems that require fire to regenerate and flourish. As such plant communities are either fire dependent or non-fire dependent. Many factors are used to determine the appropriate fire regime for a given ecosystem including climate, season, intensity, frequency and burn pattern. Fire behaviour is influenced by topography (slope, aspect and vegetation type), climate (temperature, relative humidity, wind and rainfall) and fuel characteristics (fuel load and fuel moisture content).

3.8.4 Results of Analysis 3.8.4.1 Known Fire Events

There are few known documented bushfire events recorded in the Bahrs Scrub locality and surrounds. However there was visual evidence of recent bushfire activity found in Clarkes Hill and this was confirmed by the Queensland Rural Fire Service to be a wildfire that burned through the north-east corner of Clarkes Hill in November 2008. Bushfire activity was also observed in the vicinity of Clarkes Hill in approximately 1994. The rest of the site has no record of wildfire or prescribed burning. Buccan Conservation Park, which adjoins the site to the south, has no record of bushfire in the last 10 years. Although prescribed burning is planned to be implemented in the park during spring 2010.

3.8.4.2 Vegetation

Eleven REs were identified in the site, of which two are regarded as ‘of concern’, one ‘endangered’ community and the remainder were mapped as ‘of least concern’ under the


Vegetation Management Act. Most of the site vegetation consists of grassy eucalypt and acacia forest, however areas of endangered ‘Gallery rainforest (notophyll vine forest) on alluvial plains’ (RE 12.3.1) and ‘notophyll vine forests on metamorphics’ (RE 12.11.10) are present. These vegetation communities require complete protection from bushfire. Other vegetation communities require various bushfire management practices (refer Table 3 of the bushfire report).

3.8.4.3 Slope, Aspect and Bushfire Hazard Rating

Slope and aspect account for much of the high and medium bushfire hazard rating as the site has many hills and gullies. Most of the high and medium hazard areas are located to the north-east (in the vicinity of Clarkes Hill), north and north-west of the site. Most of the low hazard areas are located over the central, east and south-east of the site, except for a high and medium hazard area which occurs in the vicinity of Bahrs Hill. The bushfire hazard mapping is shown in Figure 2 of the bushfire report (refer to Figure 3.19 below).

3.8.5 Constraints to Future Development Development within the site is likely to introduce a range of factors and issues that may conflict with potential bushfire impacts. Analysis of these has identified a number of potential constraints, including: • residential development occurring in areas of high and medium bushfire hazard, or on

ridge-tops and steep lands identified with a high and medium bushfire hazard • location of community infrastructure, institutional use facilities and high density residential

development • location of services and infrastructure supply such as roads, water, gas and electricity • retention of significant vegetation communities within an urban environment • bushfire hazards for land being developed in stages or progressively. Rather than identifying Category 1, 2 and 3 constraints to future development, it was more appropriate for the bushfire report to identify bushfire hazard ratings which can be applied to future development in the site in accordance with SPP 1/03: Mitigating the Adverse Impacts of Flood, Bushfire and Landslide (refer Figure 3.19 below).

3.8.6 Conclusions and Recommendations The report recommends a two staged approach in planning for bushfire management: 1. Phase 1 involves a whole of area approach during the plan-making phase, incorporating

bushfire safety measures and recommendations 2. Phase 2 requires bushfire protection measures to be incorporated into the subdivision

design phase to avoid development in areas of high or medium bushfire hazard where Phase 1 has unavoidably brought these areas into conflict.

Table 5 of the bushfire report outlines the broad bushfire planning principles to be considered during Phase 1 however the key principles are: • residential development, institutional uses and manufacture or storage of hazardous

material in bulk is located on land mapped as low bushfire hazard, in preference to high or medium bushfire hazard

• safety buffers shall be applied to areas of high and medium bushfire hazard of 100m and 50m respectively, in order to provide mechanisms to be implemented with these buffers zones

• consider the relationship between bushfire hazard and location of residential development (development of steep land or ridge-tops uphill from bushfire hazards is not recommended)

• provide adequate and accessible water supply for fire-fighting equipment • provide underground provision for electricity supply • consider evacuation routes through the provision of an efficient and legible road network. The GCCC Constraints Code ‘Bushfire Management Areas’ of the Gold Coast City Planning Scheme 2003 also provides additional guidance on these matters, particularly in relation to subdivision design.


Figure 3-19 Bushfire hazard severity


3.9 Concluding Comments The technical studies examined the site’s existing physical conditions and identified constraints to the future development of the site. The constraints mapping produced by the technical studies is considered together and further analysed in chapter 4 to determine a net developable/conservation area for the site. The technical studies made a range of conclusions and recommendations regarding the site constraints (refer previous sub-sections above). In broad terms, contaminated land and cultural heritage matters minimally affect the site, with lot-specific studies on these matters recommended as development applications occur in the future. Slope and geotechnical constraints have identified an uppermost limit where future buildings may be located on the site, as well as several locations that warrant geotechnical remediation. Similarly hydraulic analysis has identified the 10, 50 and 100 year ARI design flood extents for the site. The 100 year ARI design extent represents the stormwater drainage exclusion zone while the 10 year ARI design extent represents the riparian corridors in the site. Potential stormwater management solutions have been identified however this matter will need to be considered at a second stage in the plan-making process. The site has an interesting and appealing landform and is comprised of distinct character districts. The landscape and visual amenity assessment highlighted the value of the site’s landform particularly the encompassing ridges, and recommends design measures to consider in planning and designing future development. The bushfire report identified bushfire hazard areas on the site. The report highlights existing bushfire hazard areas to assist in planning and designing any future development throughout the study area. Ecological matters are the most significant of all matters to be considered for the site at this stage. The ecological assessment found that large portions of the site support vegetation of State significance that provides habitat for fauna and flora species listed as significant at the Commonwealth and State level. Large areas around Clarkes Hill and Bahrs Hill and smaller wetland communities along Windaroo Creek were recommended to be excluded from future development. It was also recommended that work be undertaken at a property level to further ascertain site values for flora and fauna.

3.0 summary of stage 1 technical studies - logan.qld.gov.au · bahrs scrub draft planning study...

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