identification of water sensitive urban design …...identification of wsud measures and approaches...

Important Notice This report applies only to the subject of the project. University does not accept responsibility for the conformity or non-conformity of any other subject to the findings of this report. This report consists of one cover page and 59 pages of text. It may be reproduced only with permission of the copyright owner, and only in full.

Educating Professionals Applying Knowledge Serving the Community

Identification of Water Sensitive Urban Design Measures and Approaches for Sustainable Stormwater Management

Report – Part A Executive Summary, Background, Multi-Criteria Analysis and Recommendations

to be read in conjunction with Reports Part B – Water Quality Part C – Harvesting, Re-use and Flood Mitigation

Prepared for Catchment Management Subsidy Scheme, Transport SA, Adelaide & Mount Lofty Ranges Natural Resources Management Board, Local Government Association and Environment Protection Authority

Prepared by Urban Water Resources Centre University contact David Pezzaniti Group Leader Telephone +61 8 8302.3652 Facsimile +61 8 8302.3386 Date of issue December, 2006

ISO 9001 QEC6382

Educating Professionals • Creating and Applying Knowledge • Serving the Community

Division of IT, Engineering and the Environment

Identification of WSUD Measures and Approaches Report – Part A

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EXECUTIVE SUMMARY This project aims to identify the most effective Water Sensitive Urban Design (WSUD) measures and strategies associated with urbanisation (development and re-development). A key element of this project has been the development of a multi-criteria decision analysis, which brings together the objectives and analysis outputs to enable selection of the most effective strategy(s).

Developing an Effective Stormwater Management Strategy for WSUD Typically, WSUD has been viewed as a water quality measure, however it is much broader and this study also assesses other elements of WSUD, that includes:

• water quality; • flooding (minor system); and • harvesting and re-use.

These are the key objectives established by the Urban Stormwater Initiative Executive Group (USIEG, 2005) for the overall strategic direction for urban stormwater management in the State. In order to identify effective WSUD measures and strategies it was important to undertake a study on a ‘real’ catchment. A case study site (Meakin Tce catchment, City of Charles Sturt) was selected for the project as it exhibits many of the opportunities and constraints experienced in the greater Adelaide metropolitan area. A range of WSUD options were then assessed at varying scales (allotment to end of catchment). The study included developing catchment models to review performance associated with water quality (MUSIC) and flooding (EPA SWMM). No water quality or flow data were available for the

QUALITY FLOODING HARVESTING/REUSE ECONOMIC SOCIAL

Assess short-listed measures and review for quality, flooding, harvesting/re-use, economic and social.

Select strategy(s) according to multi-criteria analysis outcomes.

Undertake a multi-criteria analysis that includes a ranking procedure that considers objectives and analysis outputs.

Identify and short-list preliminary WSUD measures for assessment.

Determine and rank key objectives for the catchment.



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catchment needed for calibration of the models, however some field monitoring was undertaken during the study in an attempt verify model outputs. A multi-criteria decision analysis was developed to determine the most effective strategies. The decision analysis considered quality/environmental, flooding, harvesting/reuse, economic, and social values associated with each WSUD measure. Measures were ranked based on performance with respect to a set of criteria, allowing the identification of the most effective options. The study outcomes not only intend to provide the technical justification (including economic, environmental and social values) for selected measures and strategies applicable to the case study catchment, but also provide information that may be adapted to other urbanising metropolitan catchments. It can be considered that a significant proportion of the outcomes of this project will provide the technical basis to support incorporation of WSUD elements into future planning processes for similar metropolitan Adelaide catchments undergoing urban consolidation. This project has been divided into three separate reports: Part A – Executive Summary, Background, Multi-Criteria Analysis and Recommendations Part B – Water Quality Part C – Harvesting, Re-use and Flood Mitigation This document represents Part A of the project. The findings of this report are based on detailed assessment of the water quality; harvesting, re-use opportunities and flood mitigation as presented in Parts B and C, respectively. Overall Performance of Measures for Meakin Tce Catchment The study of the Meakin Terrace catchment identified a variety of opportunities to implement water sensitive urban design (WSUD) measures at different scales (allotment to end of catchment). The study has revealed several interesting findings with regards to the most effective WSUD measures that could be implemented in the Meakin Tce catchment taking into account economic, environmental and social values. Multi-Criteria Decision Analysis Overall, when applying equal weightings to economic, environmental and social values, catchment schemes such as wetland ASR schemes and basins rank highly using a multi-criteria analysis, and usually outperform source control measures distributed across the catchment. Larger end of catchment measures such as the Royal Adelaide golf course (RAGC) ASR wetland or the Nash St reeded swale typically provided the best overall water quality performance. This result is similar to a recent multi-criteria analysis performed on a case study in Brisbane (Taylor et al, 2006) where both large and small scale wetlands outperformed bioretention devices in medians and kerbside bioretention pods. When reviewing the overall multi-criteria analysis developed for this catchment, applying equal weightings to economic, environmental and social values, for the measures investigated the following was found:


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Overall Performance Based on a Multi-Criteria Analysis for Selected WSUD Measures

Rank Option 1 The RAGC wetland ASR scheme provides the most favorable overall result. This is mainly due to

the high environmental values, including high water quality improvements and very high re-use opportunities, with a moderate cost. Flood mitigation benefits upstream however are very low.

2 A vegetated (reeded) swale adjacent to Nash St at the downstream end of the catchment results in moderate to very high pollutant removal rates at a low cost. Flood mitigation benefits and re-use opportunities however are very low.

3 Catchment ASR wetland schemes at local reserves throughout the catchment rank highly typically due to low cost and moderate to very high social values. Water re-use opportunities are moderate to high, however water quality improvements at the catchment outlet are typically low.

4 Allotment level raingardens provide a moderate to low cost option, with generally moderate reductions in flooding across the catchment. Pollutant reductions at the catchment outlet are considered low.

5 Catchment scale basins where inflow is allowed to pass through the basin offer a relatively low cost option with generally low to moderate water quality improvements at the catchment outlet and moderate to high social values. Water harvesting and re-use are considered very low.

6 Minor streetscape infiltration and filtration devices such as bioretention pods etc typically outperform minor streetscape swales. Costs will vary depending upon the extent they are applied across the catchment, however water quality improvements at the catchment outlet and reductions in flooding are considered to be low to very low. Water harvesting and re-use are also considered very low. Streetscape devices are typically more favorable for catchment areas treated of less than 20% and provide a higher value score if sized for treatment (eg 90% of average annual runoff volume).

7 Permeable pavement along major arterial road edges are typically moderate to high in cost, provide only low water quality benefits, very low reductions in flooding and very low water harvesting and re-use benefits.

8 Allotment level raintanks and major road bioretention devices located in road medians rank lowly typically resulting in high costs, with very low water quality benefit at the catchment outlet and typically moderate to very low social values. Water re-use benefits for tanks is considered to be moderate and flood mitigation benefits are considered very low.

9 On-site detention tanks are the least favored option, resulting in very high costs, very low water quality, flooding and re-use benefits and typically very low social values.

Sensitivity of Results A sensitivity analysis with more emphasis on costs resulted in similar overall ranking results, however the Nash Street reeded swale and smaller ASR wetland schemes ranked higher than the RAGC ASR wetland scheme, although value scores were not significantly different. When the environmental weighting factor was increased the RAGC ASR wetland scheme and the Nash Street reeded swale resulted in values scores


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significantly higher than other measures. This reflects the high pollutant removal efficiency of these measures as compared to other measures assessed. Further sensitivity of overall performance scores included separate categories for water quality, re-use and flooding, with greater weighting points allocated to flooding. That is, reduction in flooding in the catchment was considered a primary objective followed by re-use and water quality improvements. The RAGC ASR wetland scheme still ranked highly, although there was a shift in preference to re-use schemes distributed across the catchment. Allotment level raingardens, medium sized (eg allotment size) infiltration basins also ranked highly as well as minor road streetscape infiltration devices installed extensively across the catchment. These reflect the greater impact on reductions in flooding. Recommendations for Applying Multi-Criteria Analysis to Stormwater Management with WSUD The sensitivity analysis revealed an important limitation when using a multi-criteria decision analysis considering economic, environmental and social categories only. In such a case the key objectives with regards to the USIEG for the overall strategic direction for urban stormwater management in the State, that is quality, quantity and re-use could not be assessed separately. Typically, flooding and re-use would only be represented as one criterion each from a number of other criteria in a category, reducing their overall importance in the process, whereas water quality would typically be the driving criteria under environmental values. This results in a bias for measures that typically exhibit good water quality improvements, whilst not necessarily providing benefits with respect to flooding or re-use. In catchments where the primary objective is to reduce flooding this may result in strategies that do not provide the most effective outcome. As a recommendation, the multi-criteria analysis should be extended to separately assess water quality, flooding and re-use, whilst also still assessing economic and social benefits (refer to flowchart previously presented). In such a case weightings can be applied to categories that reflect the important objectives for stormwater management specific to the catchment. Water Quality Reduction in Loads The majority of source control WSUD measures investigated provided a low reduction (<30%) in contaminant loads at the catchment outlet. Individual basins such as at Matheson oval and Gleneagles reserve provided reductions in the order of 30 to 40 % if both are installed. The present configuration of Gleneagles basin provides minor water quality improvements as low flows bypass the basin. With a reconfiguration of this basin to allow low flows to enter the basin, contaminant loads at the outlet can be reduced by approximately 15% or more. The greatest water quality improvement measure was associated with the construction of the RAGC ASR wetland scheme where contaminant reductions of 60 to 70% at the outlet could occur. These reductions are based on a wetland size for harvesting and could be improved if a larger wetland area is used. Installation of additional WSUD measures upstream of the RAGC wetland results in only minor


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improvements in water quality at the catchment outlet, the main benefit being a reduction in load into the RAGC wetland. A reeded swale located adjacent to Nash St at the downstream end of the catchment achieved high rates of removal for solids (>75%) but lower removal rates for nutrients. WSUD infiltration systems can be an effective measure to reduce contaminant loads, but will not necessarily reduce pollutant concentrations at the catchment outlet. This is due to the reduced flow at the catchment outlet. Allotment harvesting where typically “clean” roof water is abstracted may also result in increased concentrations in the general (reduced) outflow from the catchment. It must be noted that larger scale schemes such as ASR wetlands, basins and the Nash st reeded swale provide immediate water quality improvements following construction, whereas schemes such as streetscape devices installed across the catchment with provide progressive water quality improvements as they are constructed over time. Pollutant Concentrations The study reviewed stormwater pollutant concentrations at the catchment outlet with respect to water quality criteria for governing environmental values, as per Environment Protection (Water Quality) Policy, 2003. It must be noted that the guideline values do not apply to the ultimate discharge of stormwater from a public disposal system into any waters by government or public authority responsible for the system. Also the guideline values are applicable to the receiving body as opposed to the stormwater discharge. As such the review was for comparison purposes only. Typically water quality improvements have been reviewed in terms of reductions in total loads at the catchment outlet. With no treatment measures installed in the catchment modelled pollutant concentrations for nutrients are within EPA water quality guideline limits for the environmental values relevant to the catchment (0.5 mg/l for TP and 5 mg/l for TN). Suspended solids discharge concentrations typically far exceed guideline values (10 mg/l limit) for the measures investigated. Typically, larger downstream measures would provide the greatest benefit with respect to reduction in pollutant concentrations. For example, the reeded swale adjacent to Nash St indicated a discharge suspend solids concentration in the order of 50 mg/l. It must be noted that due to the variable nature of stormwater (both discharge and loading), setting pollutant concentration guideline limits for stormwater discharges in the future may not be practical or achievable. A more suitable approach may be to set target values based on the receiving water environment. The Adelaide and Mount Lofty Natural Resource Management (NRM) Board is currently developing general water quality targets for the NRM regional plan and subsequent to this environmental values in conjunction with the EPA. Another approach being used in the eastern states is to set load reduction targets for new developments. Setting some form of target value for stormwater discharges in South Australia will be a key driver in the implementation of WSUD in the future.


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Comparison with Interstate Guideline Limits It must be noted that EPA guideline limits for nutrients are typically higher than interstate limits. This is mainly due to the influence different climate conditions (lower rainfall) has on determining the limits experienced in Adelaide. As a result, associated pollutant concentration levels for protection of aquatic ecosystems have been found to be higher. For example, water quality guideline limits for Melbourne and Brisbane are:

• Melbourne TP 0.05 mg/l; TN 0.6 mg/l • Brisbane TP 0.07 mg/l; TN 0.65 mg/l both considered at the 50% level

It can been seen that urban catchments producing similar contaminant loads in Adelaide may meet relevant local guideline limits, but would fail to meet interstate limits. This is an important point when considering appropriate reductions in contaminants for different regions. For example, typically WSUD measures applied in new developments in the eastern states will require a demonstration in load reductions of:

• 80 % TSS • 45 % TP • 45 % TN

Similar values may not be relevant in the context of urban Adelaide catchments. It must be noted however, that although nutrient levels may be within guideline values it is still desirable to manage nutrient loads to minimize potential nuisance algal growths and other adverse effects. Pollutant Removal Costs The most cost effective measures in terms of pollutant removal are associated with the larger end of catchment measures such as the RAGC ASR wetland scheme and the Nash street reeded swale. Distributed source control measures are seen to be an order of magnitude higher in cost per kilogram of pollutant removed. Harvesting and Re-use Catchment scale harvesting using ASR wetland schemes offer significant financial ($/kL) advantages compared to the combined effects of allotment level rainwater tanks. Catchment scale ASR wetland schemes will also enable sustainable long-term use of groundwater and offers additional benefits to the community such as water quality improvements, social amenity values and offer potential retail opportunities. When reviewing the total long term combined potential harvested volume for 1 kL rainwater tanks on redeveloped allotments, the maximum amount of water that could be harvested throughout the catchment at the ultimate state of development is approximately 34 ML/yr. This represents a net reduction in mains water demand to the entire catchment in the ultimate state of development of approximately 3 %. The combined tank storage throughout the catchment is approximately 1,500 kL.


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In the existing catchment there are potential opportunities for local ASR wetland schemes at the Powerhouse reserve, Ledger oval, Matheson reserve and Gleneagles reserve. It may be possible to consider a single large scheme, such as the Royal Adelaide golf course ASR, rather than several smaller schemes. The RAGC scheme could then be sized to harvest enough water to meet the equivalent total catchment demand on groundwater. That is water injected at RAGC can offset borewater extracted at any of the reserves in the catchment. There may also be the opportunity to utilize additional groundwater credit to reduce mains water open space irrigation. This would particularly be applicable for reserves that are not adjacent to the main drainage network, where diversion of catchment runoff may be difficult. Examples of such schemes occur in the Salisbury City Council area. Issues such as cost sharing would need to be considered. Although medium to large scale harvesting schemes (when available) offer advantages over allotment level rainwater tanks, allotment level schemes should not necessarily be discouraged as this promotes the culture of re-use. Larger scale schemes will typically not provide direct reticulation re-use opportunities to individual households and as such allotment level rainwater tank harvesting is still valid for Water Proofing Adelaide. Flooding (minor events) Flooding difficulties in the catchment are frequent (less than 1 year ARI) and occur due to the low capacity of the drainage system as a result of the flat topography (typically 0.2%). Two critical flooding areas identified in the catchment occur at Crittenden Rd and Tapleys Hill Rd/Meakin Tce. Assessment of WSUD systems for flood benefit focused on potential reductions in flooding volumes at the two critical points. Most WSUD measures reviewed, which were sized for water quality only (eg treating 90% of mean annual runoff), provided low (<30%) to very low (<10%) reductions in flooding volume for the 5 year ARI. Streetscape infiltration (retention) and filtration (extended detention) devices sized for a 5 year ARI distributed, across 20% or more of the catchment, enabled moderate (up to 50%) to high (50-75%) reductions in flooding volume. Allotment level raingardens installed on new or redeveloped allotments enabled moderate reductions. These reductions are improved for the more frequent events (eg 1 year ARI). With regards to WSUD, typically the most effective means of reducing flooding in the catchment using WSUD measures is associated with distributed infiltration (retention)/filtration (extended detention) devices, as opposed to storages at individual sites (for an equivalent storage volume). There may be opportunities to improve the effectiveness of such a strategy by zoning the catchment. Opportunistic Implementation of WSUD This study has identified and assessed opportunistic implementation of WSUD. These include:

• where redevelopment is to occur (eg infill development); • areas where flood mitigation measures are immanent (eg Matheson reserve with diversion

works);


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• areas where council works are planned (eg road upgrades, footpath rehabilitation etc. None are planned this financial year, but this is an on-going opportunity); and

• sites that may offer re-use benefits such as local or large scale ASR schemes (eg reserves, open space areas).

Strategic Implementation of WSUD Based on results from this study the most strategic implementation of WSUD involves:

1. Construction of the RAGC ASR wetland scheme. This scheme will provide quality and re-use benefits but will not provide flood benefits in upstream areas of the catchment.

2. Reduce mains water use into catchment by irrigating open spaces with groundwater. Build up

groundwater credits at RAGC by harvesting sufficient water at this point to meet total catchment needs for open area irrigation. This avoids the need for small and medium sized harvesting schemes across the catchment.

3. For new allotments install raingardens that allow runoff from impervious areas to be retained on

site (typically in landscaped areas). These devices can be sized to retain runoff from storm events such as the 5 year ARI and can provide a moderate reduction in flooding volume at key points across the catchment. Re-use opportunities may also be available (eg allotment bores for lawn irrigation).

4. Medium size basins in areas where flooding is of concern. The size of these devices should be

chosen to achieve desired reductions in flooding.

5. Minor road infiltration devices such as surface and subsurface storages in areas where localized flooding may be of concern and there are no opportunities for basins. The size of these devices should be chosen to achieve desired reductions in flooding.

Adaptation of Results to Other Urbanising Catchments Although the outcomes of this study are specific to the Meakin Tce catchment some of the findings are important when considering the future direction of planning policy with regards to WSUD measures applied to urban catchments undergoing consolidation. Further details on planning issues are currently being explored by Joe la Spina of The City of Onkaparinga and will be made available in the near future (Exploring Statutory Planning Issues and Implementation of Stormwater Best Management Practices – A Local Government Perspective). The flowchart presented at the start of this executive summary provides the fundamental steps to be considered when developing an effective stormwater management strategy for WSUD. Providing a generic strategy for other urbanizing catchments in Adelaide is difficult as each catchment will have specific objectives and physical characteristics that will differ from the case study catchment.


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However, the following may provide some guidance as to measures that may be considered further when developing a strategy incorporating WSUD.

• Where open space areas are available local harvesting schemes could be encouraged or vegetated cleansing schemes could be promoted. Location of such measures at the downstream end of the catchment would generally be preferred, unless upstream flooding or environmental values are of concern. Such measures can be applied to catchments with either high or low soil infiltration capacity.

• Preference for large scale harvesting schemes as opposed to small (eg allotment) to medium sized (eg local reserve) schemes. Although on-site harvesting using rainwater tanks should not necessarily be discouraged.

• For catchments with moderate to high soil infiltration capacity allotment level raingardens for new developments could be promoted as well as catchment scale infiltration basins, or minor road infiltration devices. These will typically provide benefits with regards to flooding and some water quality benefits.

• For catchments with low soil infiltration capacity minor road streetscape filtration systems such as bioretention pods could be applied strategically across the catchment, particularly in areas where flooding is of concern, or where contaminant loads are highest (eg industrial and commercial areas). These could also provide traffic calming benefits.

• Minor road infiltration/filtration devices would typically be preferred over minor roadside swales (provided sediment loads are not “excessive”).

• Major road bioretention devices in medians would not be considered practical due to costs and disruptions during road reconstruction. In fact retrofitting would require complete reconstruction of the road to enable drainage to the central median. Such works would be enormously expensive, and practically very difficult due to services etc. Road side devices such as permeable pavements would be preferred.

• On-site detention tanks would only be considered as a final option, if no other measures are applicable.

Funding of strategies may take various forms. On-site measures are typically funded by developers/homeowners through the development process, however targeted options, i.e. at a catchment level or in strategic zones, could be funded through a stormwater levy/credit system. Such forms of funding would need to take into consideration the timing of implementation.


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TABLE OF CONTENTS

EXECUTIVE SUMMARY .............................................................................................I

1 INTRODUCTION .................................................................................................. 1

2 CATCHMENT SELECTION................................................................................ 2

2.1 MEAKIN TERRACE CATCHMENT ........................................................................ 2 2.2 CATCHMENT CHARACTERISTICS ........................................................................ 4

2.2.1 Drainage .............................................................................................................................. 4 2.2.2 Land Use .............................................................................................................................. 4 2.2.3 Soils...................................................................................................................................... 4 2.2.4 Groundwater ........................................................................................................................ 4

3 WATER SENSITIVE URBAN DESIGN MEASURES ...................................... 6

3.1 CATCHMENT LEVEL MEASURES ........................................................................ 7 3.1.1 Basins................................................................................................................................... 7 3.1.2 Wetlands............................................................................................................................... 8 3.1.3 Gross Pollutant Traps.......................................................................................................... 9

3.2 STREETSCAPE LEVEL MEASURES..................................................................... 10 3.3 ON-SITE MEASURES ........................................................................................ 12

3.3.1 On-Site Detention............................................................................................................... 12 3.3.2 On-Site Retention ............................................................................................................... 13

4 ASSESSMENT OF WSUD MEASURES ........................................................... 16

4.1 RESULTS OF ASSESSMENT................................................................................ 18 4.2 NOTES ON VALUE SCORES............................................................................... 21 4.3 SENSITIVITY OF RESULTS................................................................................. 21

5 CONCLUSIONS AND RECOMMENDATIONS.............................................. 26

5.1 OVERALL PERFORMANCE ................................................................................ 26 5.2 SENSITIVITY OF RESULTS................................................................................. 27 5.3 RECOMMENDATIONS FOR APPLYING MULTI-CRITERIA ANALYSIS TO

STORMWATER MANAGEMENT WITH WSUD................................................................ 27 5.4 OPPORTUNISTIC IMPLEMENTATION OF WSUD ................................................ 28 5.5 STRATEGIC IMPLEMENTATION OF WSUD........................................................ 28 5.6 ADAPTATION OF RESULTS TO OTHER URBANISING CATCHMENTS................... 29

6 REFERENCES...................................................................................................... 31


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APPENDIX A.............................................................................................................. A.1

A.1 INTRODUCTION.......................................................................................... A.1

A.2 CATCHMENT DESCRIPTION.................................................................... A.2

A.2.1 Trimmer Parade Catchment..............................................................................................A.2 A.2.2 Stonyfell Creek Catchment................................................................................................A.2 A.2.3 New Gawler Sub-division (McKinlay Ridge) ....................................................................A.3 A.2.4 Specific Study Areas within Each Catchment ...................................................................A.3

A.3 TYPICAL URBAN STREETSCAPES .......................................................... A.3

A.4 LIMITATIONS AND OPPORTUNITIES WITHIN STREETSCAPES .. A.5

A.4.1 Portrush Road...................................................................................................................A.5 A.4.2 Tusmore Avenue................................................................................................................A.6 A.4.3 Coolibah Avenue...............................................................................................................A.7 A.4.4 Trimmer Parade................................................................................................................A.8 A.4.5 Hallville Street ..................................................................................................................A.9 A.4.6 Corella Avenue................................................................................................................ A.10 A.4.7 Teal Court ....................................................................................................................... A.12 A.4.8 Falcon Drive ...................................................................................................................A.13

A.5 COMPARISONS.......................................................................................... A.13

A.5.1 Old and New Streetscapes............................................................................................... A.13 A.5.2 Major Roads and Minor Roads....................................................................................... A.14

A.6 CONCLUSION............................................................................................. A.14

A.6.1 Existing Developments.................................................................................................... A.14 A.6.2 New Developments.......................................................................................................... A.15

A.7 REFERENCES............................................................................................... A.15

FIGURES

Figure 2-1 Meakin Tce Catchment Figure 2-2 Groundwater Wells and Salinity - Torrens Catchment (TCWMB, 2002) Figure 3-1 Basin Retrofit - Aldinga Figure 3-2 Catch Nets at Catchment Outlet to Henley/Fulham Drain Figure 3-3 Swale Retrofit in Residential Street Figure 3-4 Example of an Infiltration System in a Residential Streetscape Figure 5-1 Developing an Effective Stormwater Management Strategy for WSUD Figure A-1 Typical minor road cross section


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Figure A-2 Typical Major Road Cross Section Figure A-3 Portrush Rd Cross Section B-B Bioretention Swale Figure A-4 Halville St Cross Section A-A Infiltration Basin Figure A-5 Corella Ave Cross Section A-A Permeable Paving

TABLES

Table 3-1 Summary of WSUD Measures Table 4-1 Assessment Criteria and Weights Table 4-2 Assessment Criteria Performance Score Table 4-3 Multi-criteria Analysis Value Scores and Rankings – Equal Weightings for

Each Category Table 4-4 Multi-Criteria Analysis Value Score and Rankings – Economic Weighting

Increased to 50% Table 4-5 Multi-Criteria Analysis Value Score and Rankings – Environmental

Weighting Increased to 50% Table 4-6 Multi-Criteria Analysis Value Score and Rankings - Water Quality, Flooding

and Re-use Categories Included


Urban Water Resources Centre, University of South Australia Page 1 of 32

1 INTRODUCTION This project seeks to identify the most effective Water Sensitive Urban Design (WSUD) measures and strategies associated with urbanisation (development and re-development) that provide benefits with respect to water quality, flooding and re-use. These are the key objectives established by the Urban Stormwater Initiative Executive Group (USIEG, 2005) for the overall strategic direction for urban stormwater management in the State. This study is closely aligned with the USIEG’s directive and will aim to:

• assess and identify WSUD measures and strategies (from allotment to catchment level) for a case study catchment based on environmental, economic and social values;

• undertake a focussed assessment of measures and strategies that can be practically achieved taking into consideration desirable and acceptable outcomes; and

• provide the technical justification for selected WSUD measures and strategies for possible inclusion into development plans, approval processes etc.

Assessment of WSUD measures is performed using a multi-criteria analysis to indicate the most effective strategies with regards to economic, environmental and social values. Although the project outcomes intend to be applicable to the case study catchment, some of the outcomes may be adapted to other similar urbanising catchments in Adelaide.



2 CATCHMENT SELECTION The project seeks to identify effective WSUD strategies and approaches for a case study catchment with a view to incorporate results into development and planning processes on a wider scale. The catchment selected for study required an urban catchment that represented important characteristics of the wider Adelaide metropolitan area undergoing urban consolidation. Following a review of the recent Metropolitan Adelaide Stormwater Management Study (KBR, 2004), the areas of highest potential for urban consolidation are considered to be within the western suburbs (Cities of West Torrens and Charles Sturt) and north eastern suburbs (Cities of Campbelltown and Tea Tree Gully). Specific catchments identified include the Meakin Terrace, Trimmer Parade, Port Road, Dry Creek and Third to Fifth Creek catchments.

2.1 Meakin Terrace Catchment Following discussions with stakeholders, the Meakin Terrace catchment was chosen for further study for several reasons, including:

• mostly residential catchment which will be undergoing significant urban consolidation in the future;

• flooding problems have been identified; • potential re-use opportunities are available; and • detailed studies of the catchment are available, including flood plain mapping.

The catchment area is indicated in Figure 2.1.



N

Figure 2-1 Meakin Tce Catchment

Main drainage line



A recent Initial Urban Stormwater Master Plan for the Meakin Terrace catchment (Tonkin, 2003), provides information related to the hydrology of the catchment, land use (current and future), soils and drainage infrastructure and also provides information on stormwater management objectives and strategies.

2.2 Catchment Characteristics The total catchment area is approximately 411 ha and includes the suburbs of Beverly, Woodville South, Findon, Kidman Park, Seaton and Grange. The area is very flat and flooding has been identified on a frequent basis at the following locations (Tonkin, 2003):

• Tapleys Hill Road/ Meakin Terrace intersection; • Crittenden Road; • Pioneer Street/Lucerne Grove intersection; • Prior Avenue/Wilford Avenue intersection.

2.2.1 Drainage The main drainage line for the catchment runs beneath Crittenden Road, Findon Road, Angley Avenue, Meakin Terrace prior to discharging to the Henley/Fulham drain at Nash Street (refer to Figure 2.1). Ultimately runoff from the catchment enters West Lakes which is connected to the Port River estuary. Previous modelling of the catchment drainage infrastructure has indicated that the current underground drainage system has less than a 2 year ARI design capacity based on the existing level of development.

2.2.2 Land Use Land use in the catchment is mostly residential with some commercial and industrial areas in the upstream region of the catchment and along major roads. Tonkin (2003) identified the following land use values:

• residential: 60% • commercial: 4% • industrial: 2 % • open space: 10 % • other (including road reserves): 24 %

2.2.3 Soils Soils in the area are predominately red brown earth, except at the western end of the catchment where estuarine muds and sands are present. Infiltration capacity of the red brown earth soils is moderate to high, and relatively rapid for the estuarine muds and sands.

2.2.4 Groundwater The depth to groundwater in the upper quaternary aquifer ranges from approximately 8 m at the head of the catchment to approximately 2 m in the flatter coastal areas. Salinity is variable ranging from less than 1,000 mg/l to over 5,000 mg/l. Yields are typically less than 4 l/s and highly variable. Tertiary aquifers



(T1 and T2) vary in depth from the surface but are greater than 100 m. T1 aquifer contains the best quality groundwater with yields of 5 to 15 l/s. Tertiary aquifers have the potential to store large amounts of water, and would be suitable for ASR schemes, particularly at the downstream end of the catchment where demand is depleting supplies (Tonkin, 2003). Figure 2.2 presents a map of groundwater wells and salinity in the Torrens catchment (TCWMB, 2002).

Figure 2-2 Groundwater Wells and Salinity - Torrens Catchment (TCWMB, 2002)

General catchment area



3 WATER SENSITIVE URBAN DESIGN MEASURES Table 3.1 presents a summary of WSUD measures to be considered as part of this study.

Table 3-1 Summary of WSUD Measures

Short-listed Structural BMPs Applicability of BMPs Greenfield Development Urban Consolidation/Infill Primary Treatment Measures (targets litter and coarse sediments) Gross pollutant traps Including proprietary in-line products, litter baskets in pits, floating booms and trash rack/nets

Mostly applicable in areas of high litter load eg shopping centres, schools etc.

Suitable at strategic locations such as inlet to receiving waters, wetlands or areas of high litter load such as commercial and industrial sites.

Sedimentation basins May include ornamental ponds or more formal basin structures.

Suitable to trap coarse sediment upstream of other treatment measures. Highly applicable during the construction phase.

Limited by space constraints. May be incorporated into public open space, detention basins, wetlands etc.

Rainwater tanks Can provide an additional source of water for indoor and outdoor use. Reduces hydraulic loading on downstream treatment systems.

Mandatory for new dwellings from July 2006. May include individual tanks or a tank serving a cluster of dwellings. Maximum tank size may be limited due to available space on each allotment.

Secondary Treatment Measures (targets suspended solids and some nutrients and heavy metals) Kerbline buffer strips Trap and prevent sediment entering adjacent road drainage system.

Can be incorporated easily into streetscape as part of the stormwater conveyance system.

Limited by space constraints on road verges. Typically older areas have more potential for incorporation.

Vegetated swales Can be used as an alternative to conventional drainage systems for small developments (up to 5 ha).

Can be incorporated into streetscape as part of the stormwater conveyance system. Best accommodated on single cross fall streetscapes on opposite side to underground services.

Limited by space constraints on road verges and underground services. Typically older areas have more potential for incorporation. Retrofitting will require driveway reconstruction at crossings.

Infiltration systems Can reduce off site runoff. Systems include permeable pavements, gravel trenches and basins. Mostly suited to collecting roof and/or paved area runoff from residential allotments and buildings. Can help store water in flood prone areas.

Limited by soil infiltration capacity. Typically include on-site permeable pavements and infiltration trenches or basins serving a larger area. Fouling can occur when excessive sediment loads are experienced.

Limited by soil infiltration capacity, space constraints and underground services. Generally older areas have potential for above ground installations, whereas newer areas generally require below ground installations. Public open space areas can incorporate basins.

Sand filters Filter runoff through a sand bed. Generally not appropriate for disturbed catchments or areas with high sediment loads.

Generally other systems such as swales, bioretention devices, wetlands etc preferred in Greenfield developments.

They can be retrofitted into existing drainage systems. Underground services may limit use. Are most appropriate when above ground installations are not possible.



Short-listed Structural BMPs Applicability of BMPs Greenfield Development Urban Consolidation/Infill Bioretention systems Although bioretention systems can remove fine and soluble pollutants, and thus be considered tertiary treatment measures, effectiveness will depend on residence times, which can be relatively short when applied in urban settings. Also add amenity to streetscapes.

Highly applicable particularly when used at the downstream end of treatment measures such as swales prior to discharge.

Limited by space constraints and underground services. Most appropriate at the streetscape level. For major roads median strips may offer potential, for minor roads verges and roundabouts may be suitable or can also be constructed as a traffic calming measure. May also be appropriate in public open space areas. Retrofitting will most likely require significant reconstruction.

Tertiary Treatment Measures (targets finer sediments, dissolved pollutants, nutrients and heavy metals) Wetlands/Reed Beds Can provide high sediment and nutrient removal efficiencies. Provide a habitat for wildlife and add to public amenity. Can be used in conjunction with ASR schemes.

Can be integrated with the stormwater conveyance system.

Limited use in existing developments due to space constraints. Public open space, existing waterways/channels or golf courses may provide opportunities.

The following describes measures selected for further assessment based on the potential inclusion into the Meakin Tce catchment. It must be noted that although inclusion of measures are technically feasible, there are many aspects of implementation that may limit or constrain use. These are explored further in the study.

3.1 Catchment Level Measures

3.1.1 Basins In the study undertaken by Tonkin (2003), catchment wide detention basins in strategic locations were presented as one of the preferred options for stormwater management. Although this is a flow control measure, stormwater quality improvements are also possible through sedimentation and filtration processes detention systems can potentially offer. Figure 3.1 shows an example of a basin retrofit in Aldinga.



Figure 3-1 Basin Retrofit - Aldinga

Opportunities Currently an off-line capacity relief storage basin is located at Gleneagles reserve. Two additional areas identified by Tonkin include the Royal Adelaide Golf Course and Matheson reserve. In the case of Matheson reserve, the basin could be constructed in conjunction with the proposed diversion drain diverting flows from the intersection of Crittenden Road/Findon Road to the outfall at the Henley/Fulham drain. Constraints Limited open space areas are available for large scale detention basins in the catchment. Alternatively, small scale basins could be constructed as land becomes available in the catchment (eg older housing trust areas). However, this would require acquisition of the land.

3.1.2 Wetlands Wetlands have also been identified as warranting further investigation by Tonkin in their management strategies for the catchment. Wetlands provide water quality improvements and can be combined with harvesting schemes for water re-use. Opportunities

• construction of wetlands in association with local basins; • small scale ASR schemes with wetlands such as at the Powerhouse reserve, Ledger oval,

Matheson oval and Gleneagles reserve ; • possible reed bed system at Nash Street;



• possible wetland system/ASR scheme at the Royal Adelaide Golf Course (RAGC); and • possible wetland system along Henley/Fulham drain.

Detailed design of the ASR scheme at the RAGC is currently being carried out. This will include a series of wetlands and holding basins prior to aquifer injection. Constraints Wetlands constructed in open areas such as reserves may limit the use of the reserve for recreational purposes.

3.1.3 Gross Pollutant Traps Catch nets at the outlet of the Meakin Tce catchment to the Henley/Fulham drain intercepts gross pollutants such as litter and leaves. These are shown in Figure 3.2. A gross pollutant trap and sedimentation basin is also located at the downstream end of the Henley/Fulham drain, prior to discharge to West Lakes. This trap/basin also treats discharge from the adjacent Trimmer Parade catchment.

Figure 3-2 Catch Nets at Catchment Outlet to Henley/Fulham Drain

Opportunities The Initial Urban Stormwater Master Plan for the Meakin Terrace catchment (Tonkin, 2003) recommends construction of strategically located gross pollutant traps. This includes an investigation into identifying key locations having regard to pollutant loads, access and cost. Strategic locations may include:

• commercial and industrial areas, particularly in the Beverly area; and • inlets to wetlands, basins and infiltration devices.



Constraints Due to the flat topography of the catchment inclusion of in-line gross pollutant traps would require careful consideration to avoid adverse flooding due to backwater effects.

3.2 Streetscape Level Measures A recent study undertaken for the University of South Australia (West, 2005; see Appendix A) investigated how WSUD methods and approaches could be implemented into a typical urban streetscape, with consideration given to infrastructure and underground services. Typical streetscapes (major and minor roads) from different catchments across Adelaide were reviewed and limitations and opportunities for incorporating WSUD were discussed. Both old and new streetscapes were reviewed. The main findings of the study included:

• Major roads have limited opportunities to implement WSUD systems due to space constraints and extensive number of services and infrastructure. Major roads tend to be characterized by wide road pavement with very little verges.

• Minor roads in older areas were found to be most suitable for above ground applications whereas newer areas were found to be most suitable for below ground applications. Road reserves in newer developments tend to be narrower.

• There is little opportunity to implement WSUD systems within an established road carriageway without significant redevelopment of the streetscape.

Figure 3.3 shows an example of a swale retrofit in an existing residential road streetscape.

Figure 3-3 Swale Retrofit in Residential Street



Opportunities At a streetscape level, the above indicates that more opportunities for WSUD are available along minor roads such as residential collector roads. WSUD measures may include kerbline buffer strips, vegetated swales, infiltration systems (eg permeable pavements, gravel trenches and basins), and filtration systems (eg bioretention pods). For the Meakin Tce catchment priority could be given initially to areas where infill development is most likely to occur in the short term. For example Kidman Park, Seaton, areas of Woodville South and Bridgeman road. Based on study outcomes by West (2005) and the moderate to high infiltration capacity of the soil, opportunities for streetscape infiltration systems distributed across the catchment are available. Streetscape filtration systems (eg bioretention pods) and swale systems are also considered. Suitable locations for incorporation of measures include:

• traffic calming measures in minor road streetscapes (infiltration and filtration); • minor road verges (infiltration/filtration/swales); • round-abouts (infiltration/filtration) • major road medians and edges (infiltration/filtration)

Constraints Although there are many streetscape measures that may be considered technically feasible there are many aspects of implementation that need to be considered that may limit inclusion. These include:

• space available; • underground services; • disruption to traffic flow; • sediment loads; • community acceptance; and • inconvenience caused to public.

Figure 3.4 shows an example of incorporating an infiltration system into a residential road streetscape (West, 2005). Note typical location of services.



Figure 3-4 Example of an Infiltration System in a Residential Streetscape

As streetscape measures generally require retrofitting, staging of works would most likely be opportunistic during Council upgrades and reconstruction of road areas. According to the City of Charles Sturt no roads in the catchment are scheduled for reconstruction in the coming year.

3.3 On-Site Measures On-site measures typically are provided to address flooding problems due to urban consolidation or to provide re-use opportunities to households. On-site detention and on-site retention are two strategies that are commonly promoted by Councils. Such strategies enable implementation as development proceeds, with the costs initially borne by the developer/resident. On-site strategies however not only rely on individual property owners to maintain the systems but may also require a great deal of effort by Council to ensure systems are installed and functioning correctly. There is also still some conjecture as to the overall effectiveness of such policies, particularly with regards to flood attenuation.

3.3.1 On-Site Detention Although not strictly a WSUD measure, on-site detention policies are currently in place in several metropolitan Councils across Adelaide. Opportunities An on-site detention strategy is typically applicable to new or re-developed allotments. Systems may include above or belowground tanks or surface detention areas such as garden areas or depressed impervious areas. A restricted outlet controls outflow from the systems. Constraints The UWRC recently completed a review of the Campbelltown City Council detention policy (UWRC, 2005 and 2006). The study involved inspection of on-site detention devices, a community survey and



hydrologic and hydraulic modelling of a representative catchment in the area to determine the effectiveness of the policy as infill development and re-development proceeds. Other strategies for flood mitigation such as on-site retention and catchment wide detention/retention storage were also investigated. Some of the key findings of the study included:

• a significant proportion of installations were not installed as per Council requirements; • a strong community preference for either on-site retention (rainwater tank) or catchment wide

strategies rather than on-site detention; • flow attenuation at the downstream end of the catchment to pre-redevelopment levels can not be

achieved using the current policy; • on-site retention and catchment wide grouped detention enabled greater peak flow reductions

than on-site detention; and • the cost of on-site detention (per unit volume) is significantly greater than equivalent catchment

wide strategies. Several studies (Still and Bewsher, 1999; UWRC 2006) have highlighted the difficulties and problems associated with on-site detention systems, and are generally considered only when other strategies are not feasible. This supports Tonkin’s (2003) recommendation that on-site measures for the Meakin Terrace catchment should only be investigated following assessment of the local detention basin strategy.

3.3.2 On-Site Retention On-site retention systems retain runoff on-site and can also allow for re-use opportunities such as in-house and outdoor watering. On-site systems may include rainwater tanks, soakage trenches, permeable pavements and raingardens. On-site systems can thus provide both quantity and quality improvements and will also improve the effectiveness of downstream treatment systems by reducing the hydraulic loading. Rainwater Tanks Opportunities From July 2006 all new dwellings must have a rainwater tank (1,000 litre minimum) installed and connected in house for use. Alternative strategies such as allowing some portion of the tank to provide stored water for household use whilst still providing a detention capacity above this volume could also be considered. This would satisfy the new rainwater tank policy requirement and potentially provide some benefit with respect to peak flow reduction. Constraints Although rainwater tanks will reduce potable mains water demand, the impact on peak flows is not expected to be significant. This is mainly due to the expected available retention storage prior to a storm event such as the 5 year ARI. For example, previous continuous modelling undertaken by the UWRC for an urban catchment in Glenelg (Pezzaniti, 2003) indicated that for 2 kL tanks and an in-house use of 150 litres per day (typical for in-house connections such as toilet flushing and laundry), no retention storage was available for the critical storm (45 minute 5 year event). As such the tank would not provide any



reduction in peak flows during the 5 year ARI. For a 4.5 kL tank and a daily in-house use of 300 litres (typical for higher use in-house connections such as hot water, laundry etc), a retention storage of approximately 2,000 litres was available prior to the critical storm. Thus it would seem that relying on in-house use to provide sufficient retention storage for peak flow reduction would require large tank sizes. The practicalities and public acceptance of providing large above ground tanks on typically smaller new allotments would probably limit tank sizes to no greater than 2 kL. For example approximately 40 % of respondents from the recent Campbelltown survey (UWRC, 2005) indicated that a 2,000 litre tank was considered too big for their back yard space. As an alternative, draining retained water slowly to the garden area or to the street drainage over a period of 24 to 36 hours could be considered to be a more favorable means of emptying tanks, without the need for excessively large tanks. In the case of draining water to lawn areas the homeowner will also gain some benefit from the stored water. Alternatively, underground storages could be considered. Permeable Pavements Installation of permeable pavements on areas such as driveways can allow reductions in the amount of directly connected impervious area to the street drainage system for minor storm events. Other impervious surface areas on the allotment and rainwater tank overflow can also be directed to the permeable pavement surface. Opportunities Due to the moderate to high infiltration capacity of the soils in the area such a strategy could be considered applicable throughout the catchment as re-development proceeds. In particular, permeable pavements would be most appropriate for new allotments with little or no pervious lawn area as well as developments in flood prone areas. Even without infiltration to the surrounding soil (eg in areas with low infiltration rates or where infiltration may cause damage to road pavements etc), permeable pavements are capable of retaining approximately 30 mm of intense rainfall. Constraints May be limited in use for small allotments or areas where soil infiltration capacity is low. Raingardens Raingardens consisting of a localised depression storage area incorporated into the allotment landscape can be used to temporarily store discharge from roof and impervious areas prior to infiltration. Opportunities Due to the moderate to high infiltration capacity of the soils in the area such a strategy could be considered applicable throughout the catchment as re-development proceeds. Raingardens could be sized to drain relatively quickly to minimize inconvenience flooding of lawn areas. This will reduce the flow to



the street drainage system, particularly for the minor storm events. This may offer an effective way of minimizing the impact on peak flows from urban consolidation. Constraints Some re-developed allotments may have limited area available for incorporation of raingardens. Low soil infiltration capacity may also limit use.



4 ASSESSMENT OF WSUD MEASURES Assessment of selected measures is undertaken using multi criteria decision analysis (Taylor, 2005). Multi criteria analysis allows a triple bottom line assessment of each measure by dividing the assessment criteria into three main categories, that is:

o economic; o environmental; and o social values.

Each category is given equal weighting points of 33.3 points to give a total of 100 points. Under each category assessment criteria are assessed. These criteria are given weightings from a score of 1 to 10, where 10 indicates the criteria is extremely important. Weighting points for each criterion are adjusted to maintain 33.3 points for each category. Under each assessment criterion performance scores are assigned to each measure depending on how the measure performs. Performance scores of 1 to 5 are assigned to each measure, where 5 represents the most desirable result and 1 the least. Where measures are quantifiable (eg costings and water quality improvements) suitable ranges are developed to best represent the relative performance (refer to Table 4.2). Finally, performance scores are multiplied by weighting values for each criterion and are then summed for each measure to provide a final score. This process is applied to each WSUD measure in order to provide an overall “value score”. This allows WSUD measures to be ranked. The assessment criteria for the study and scoring system are indicated in Tables 4.1 and 4.2. It must be noted that the assessment criteria developed considers an equal “likelihood score”. Likelihood scores reflect how likely it is that the option will perform to the extent indicated by the performance score. Typically, new technologies will have lower likelihood scores than well known alternatives due to uncertainties that may be associated with the performance of such measures. This can result in a significant disadvantage to promising new technologies in the assessment process.



Table 4-1 Assessment Criteria and Weights



Table 4-2 Assessment Criteria Performance Score

Criteria Performance Score

5 4 3 2 1

Financial/Economic

Total acquisition cost. Includes feasibility studies, design, construction, project management.

Very low (<$250k)

Low ($250-$500k)

Moderate ($500-$750k)

High ($750-$1M)

Very high (>$1M)

Typical annual maintenance cost Very low (<$10k)

Low ($10-20k)

Moderate ($20-50k)

High ($50-

$100k)

Very high (>$100k)

Life cycle cost. Sum of all discounted costs over the life of the measure.

Very low (<$500k)

Low ($500k-$1M)

Moderate ($1M-$2M)

High ($2M-$4M)

Very high (>$4M)

Environmental/Ecological

Pollutant reduction efficiency – TSS load at outlet

Very high (>75%)

High (50-75%)

Moderate (30-50%)

Low (10-30%)

Very low (<10%)

Pollutant reduction efficiency – TP load at outlet

Very high (>75%)

High (50-75%)

Moderate (30-50%)

Low (10-30%)

Very low (<10%)

Pollutant reduction efficiency – TN load at outlet

Very high (>75%)

High (50-75%)

Moderate (30-50%)

Low (10-30%)

Very low (<10%)

Water re-use opportunities (based on annual amounts)

Very high (>100 ML)

High (50-100

ML)

Moderate (25-50 ML)

Low (10-25 ML)

Very low (<10 ML)

Social

Community acceptance Very high High Moderate Low Very low

Improvement in general amenity (eg general attractiveness of the area)

Very high High Moderate Low Very low

Maintenance burden for local residents Very low Low Moderate High Very high

Safety hazards (eg drowning hazard, health hazards during maintenance etc)

Very low Low Moderate High Very high

Equity Very high High Moderate Low Very low

Multi-use of BMP Very high High Moderate Low Very low

Inconvenience associated with BMP (eg nuisance flooding, restriction in use etc)

Very low Low Moderate High Very high

Reduction in flooding volume (based on 5 year ARI at Critteneden Rd and Tapleys Hill Rd/Meakin Tce)

Very high (>75%)

High (50-75%)

Moderate (30-50%)

Low (10-30%)

Very low (<10%)

4.1 Results of Assessment Performance values are derived from water quality modelling (Report B), harvesting, re-use and water quantity modelling (Report C) as well as life cycle costing adapted from Fletcher (2005). Costs have been adapted from default costs derived from Australian studies that are used in MUSIC (Fletcher, 2005). Life cycle costs consider a time span of 50 years with an inflation rate of 2 % and a



discount rate of 5.5 %. Life cycle costs include all expenses associated with acquisition, operation, maintenance, refurbishment, discarding and disposal. Typically, land acquisition costs and road reconstruction costs are not included. These are taken as either already owned (land acquisition) or undertaken during necessary road reconstruction works. The exception to this are measures associated with allotment sized basins where land acquisition costs have been included. When estimating water quality performance scores, load reductions at the catchment outlet, as compared with the pollutant loads with no treatment measures applied, are taken. No social surveys were undertaken as part of this project, as such social values for each criteria are based on previous studies, where applicable. One such study includes a survey of homeowners in the Campbelltown City Council (UWRC, 2005) on on-site detention tanks. Other studies (eg Lloyd et al 2002, Lloyd 2004) have reviewed social acceptance of bio-filtration systems in streetscapes, wetlands and re-use schemes; as well as increases in property values due to stormwater management measures such as ponds, landscaped areas etc (US EPA, 2001; Ferderick et al 2001). Reductions in flooding are taken at two key points in the catchment along Crittenden Rd and Tapleys Hill Rd/Meakin Tce intersection, as described in Report C. Comparisons are made with regards to reduction in flooding volume at the 5 year average recurrence interval. Table 4.3 provides details of the performance scores allocated to each WSUD measure in terms of how they perform against each of the assessment criteria, together with the resulting value scores for each measure. Overall rankings are also indicated.



Table 4-3 Multi-criteria Analysis Value Scores and Rankings – Equal Weightings for Each Category

Note: MARV refers to the mean annual runoff volume. In the current case a MARV of 2.6% represents a storage volume that will treat 90% of the mean annual runoff. A MARV of 5.4% represents a storage volume that will contain the runoff from a 5 year 60 minute storm.



4.2 Notes on Value Scores The following provides some important notes on the derivation of value scores in Table 4.3:

• Streetscape minor road filtration devices (eg bioretention devices) are given a high amenity value as these systems can be landscaped and add to the overall appearance of a streetscape. Streetscape minor road infiltration devices are given a very low amenity value as these are usually below ground devices.

• Streetscape minor road swales are given a low amenity value as these will normally be located in street verges and may not necessarily add to the amenity. A high inconvenience value is also assigned as swales may reduce the use of verges for pedestrians and will also require driveway reconstructions. Road reconstruction may also be required to direct flow to a swale located on one side of the street.

• For increasing percentages of streetscape infiltration/filtration devices the inconvenience value increases from very low to moderate. This is mainly associated with the increasing disruption to traffic flow (ie using these devices as traffic calming measures) in residential streets with an increasing number of streetscape devices across the catchment.

• The inconvenience value associated with major road bioretention medians is very high due to the reconstruction of the road section to direct flow toward the median. This would have a major impact of traffic flow during reconstruction. For permeable pavement along road edges the value is reduced to low as only the edge of the roads are affected and would not be expected to cause major traffic disruptions.

• Equity values for allotment level measures are considered very low as only homeowners with devices are affected. For larger scale catchment schemes the equity value increase to very high indicating that the whole community may benefit from the measure.

• Community acceptance of catchment scale ASR wetland schemes throughout the catchment is taken as moderate as there may be some objection due to reduced recreational use of reserves. In the case of RAGC ASR wetland community acceptance is taken as very high indicating that the impact on community use is very low.

• Improvement in general amenity and equity values for the RAGC wetland ASR are taken as very low due to the fact that the benefits are only available to users of the golf club and not the whole community.

4.3 Sensitivity of Results In order to review results the weighting factors applied to each triple bottom line category were adjusted to place more importance on the economic and environmental factors (previously each category was equally weighted with 33.3 points). The following weighting points were used for each category:

Case 1 Economic 50 points, Environmental 25 points, Social 25 points Case 2 Economic 25 points, Environmental 50 points, Social 25 points

Table 4.4 and 4.5 provides details of the resulting value scores for each measure with the revised weighting. Overall rankings are also indicated.



Table 4-4 Multi-Criteria Analysis Value Score and Rankings – Economic Weighting Increased to 50%




Table 4-5 Multi-Criteria Analysis Value Score and Rankings – Environmental Weighting Increased to 50%




A further test was undertaken to review the overall performance by including separate categories for water quality, water quantity, and re-use as well as financial and social categories. Previous assessment included these categories as criteria under the main triple bottom line categories (financial, economic and social values), however there is the possibility of bias for systems that perform well in terms of quality but provide little flooding or re-use benefits using this method. For the Meakin Tce catchment it was considered that issues related to reduction in flooding were of primary concern followed by re-use and water quality improvements. Water quality improvements, although desirable may not be considered of primary concern due to systems in place downstream of the catchment such as the reeded outlet channel connecting to West Lakes, as well as the West Lakes sea water re-circulation system. Table 4.6 provides details of the resulting value scores for each measure with revised weightings reflecting a greater importance associated with flooding improvements. Overall rankings are also indicated. In the development of this table the following weighting points were allocated to each category:

• Economic: 20 points • Water quality: 15 points • Re-use: 15 points • Flooding: 30 points • Social: 20 points



Table 4-6 Multi-Criteria Analysis Value Score and Rankings - Water Quality, Flooding and Re-use Categories Included




5 CONCLUSIONS AND RECOMMENDATIONS

5.1 Overall Performance The study has identified some important findings with regards to the most effective WSUD measures that could be implemented in the Meakin Tce catchment taking into account economic, environmental and social values. Overall, when applying equal weightings to financial, environmental and social benefits, catchment schemes such as wetland ASR schemes and basins rank highly, and usually outperform source control measures distributed across the catchment. This result is similar to a recent case study in Brisbane (Taylor et al, 2006) where both large and small scale wetlands outperformed bioretention devices in median and kerbside pods. When reviewing the overall multi-criteria analysis of measures investigated, applying equal weightings to economic, environmental and social values, the following was found:

1. The RAGC wetland ASR scheme provides the most favorable overall result. This is mainly due to the high environmental values, including high water quality improvements and very high re-use opportunities, with a moderate cost. Flood mitigation benefits upstream however are very low.

2. A vegetated (reeded) swale adjacent to Nash Street at the downstream end of the catchment

results in moderate to very high pollutant removal rates at a low cost. Flood mitigation benefits are re-use opportunities however are very low.

3. Catchment ASR wetland schemes at local reserves throughout the catchment rank highly

typically due to low cost and moderate to very high social values. Water re-use opportunities are moderate to high, however water quality improvements at the catchment outlet are typically low.

4. Allotment level raingardens provide a moderate to low cost option, with generally moderate

reductions in flooding across the catchment. Pollutant reductions at the catchment outlet are considered low.

5. Catchment scale basins where inflow is allowed to pass through the basin offer a relatively low

cost option with generally low to moderate water quality improvements at the catchment outlet and moderate to high social values. Water harvesting and re-use are considered very low.

6. Minor streetscape infiltration and filtration devices such as bioretention pods etc typically

outperform minor streetscape swales. Costs will vary depending on the extent they are applied across the catchment, however water quality improvements at the catchment outlet and reductions in flooding are considered to be low to very low. Water harvesting and re-use are also considered very low. Streetscape devices are typically more favorable for catchment areas treated of less than 20% and provide a higher value score if sized for treatment (eg 90% of average annual runoff volume).



7. Permeable pavement along arterial road edges are typically moderate to high in cost, provide only low water quality benefits at the catchment outlet, very low reductions in flooding and very low water harvesting and re-use benefits.

8. Allotment level raintanks and major road bioretention devices located in road medians ranked

lowly typically resulting in high costs, with very low water quality benefit at the catchment outlet. Water re-use benefits for tanks is considered to be moderate and flood mitigation benefits are considered very low.

9. On-site detention tanks are the least favored option, resulting in very high costs, very low water

quality, flooding and re-use benefits and typically very low social values.

5.2 Sensitivity of Results A sensitivity analysis putting more emphasis on costs resulted in similar overall ranking results, however the Nash Street reeded swale and smaller ASR wetland schemes ranked higher than the RAGC ASR wetland scheme, although value scores were not significantly different. When the environmental weighting factor was increased the RAGC ASR wetland scheme and the Nash Street reeded swale resulted in values scores significantly higher than other measures. This reflects the high pollutant removal efficiency of these measures as compared to other measures assessed. Further sensitivity of overall performance scores included separate categories for water quality, re-use and flooding, with greater weighting points allocated to flooding. That is, reduction in flooding in the catchment was considered a primary objective followed by re-use and water quality improvements. The RAGC ASR wetland scheme still ranked highly, although there was a shift in preference to re-use schemes distributed across the catchment. Allotment level raingardens, medium sized (eg allotment size) infiltration basins also ranked highly as well as minor road streetscape infiltration devices installed extensively across the catchment. These reflect the greater impact on reductions in flooding.

5.3 Recommendations for Applying Multi-Criteria Analysis to Stormwater Management with WSUD

The sensitivity analysis revealed an important limitation when using a multi-criteria decision analysis considering economic, environmental and social categories only. In such a case the key objectives with regards to the USIEG for the overall strategic direction for urban stormwater management in the State, that is quality, quantity and re-use could not be assessed separately. Typically, flooding and re-use would only be represented as one criterion each from a number of other criteria in a category, reducing their overall importance in the process, whereas water quality would typically be the driving criteria under environmental values. This results in a bias for measures that typically exhibit good water quality improvements, whilst not necessarily providing benefits with respect to flooding or re-use. In catchments where the primary objective is to reduce flooding this may result in strategies that do not provide the most effective outcome.



As a recommendation, the multi-criteria analysis should be extended to separately assess water quality, flooding and re-use, whilst also still assessing economic and social benefits (refer to flowchart previously presented). In such a case weightings can be applied to categories that reflect the important objectives for stormwater management specific to the catchment.

5.4 Opportunistic Implementation of WSUD A key element of an effective strategy for targeting quality and quantity improvements for WSUD measures will be identifying opportunistic implementation. These could include:

• where redevelopment is expected to impact the most; • areas where flood mitigation measures are immanent; • areas where council works are planned (eg road upgrades, footpath rehabilitation etc); and • sites that may offer re-use benefits such as local or large scale ASR schemes.

5.5 Strategic Implementation of WSUD Based on results from this study the most strategic implementation of WSUD involves a “yield maximum” approach (Argue et al 2004). That is, a strategy that maximizes stormwater runoff yield together with WSUD measures that minimize flooding and improve water quality. To achieve such a strategy the following would be considered appropriate:

1. Construction of the RAGC ASR wetland scheme. This scheme will provide quality and re-use benefits but will not provide flood benefits in upstream areas of the catchment.

2. Reduce mains water use into catchment by irrigating open spaces with groundwater. Build up

groundwater credits at RAGC by harvesting sufficient water at this point to meet total catchment needs for open area irrigation. This avoids the need for small and medium sized harvesting schemes across the catchment.

3. For new allotments install raingardens that allow runoff from impervious areas to be retained on

site (typically in landscaped areas). These devices can be sized to retain runoff from storm events such as the 5 year ARI and can provide a moderate reduction in flooding volume at key points across the catchment. Re-use opportunities may also be available (eg allotment bores for lawn irrigation).

4. Medium size basins in areas where flooding is of concern. The size of these devices should be

chosen to achieve desired reductions in flooding. 5. Minor road infiltration devices such as surface and subsurface storages in areas where localized

flooding may be of concern and there are no opportunities for basins. The size of these devices should be chosen to achieve desired reductions in flooding.



5.6 Adaptation of Results to Other Urbanising Catchments Although the outcomes of this study are specific to the Meakin Tce catchment some of the findings are important when considering the future direction of planning policy with regards to WSUD measures applied to urban catchments undergoing consolidation. The following flowchart provides a summary of the fundamental steps to be considered when developing an effective stormwater management strategy for WSUD.

Figure 5-1 Developing an Effective Stormwater Management Strategy for WSUD

Providing a generic strategy for other urbanizing catchments in Adelaide is difficult as each catchment will have specific objectives and physical characteristics that will differ from the case study catchment. However, the following may provide some guidance as to measures that may be considered further when developing a strategy incorporating WSUD.

• Where open space areas are available local harvesting schemes could be encouraged or vegetated cleansing schemes could be promoted. Location of such measures at the downstream end of the catchment would generally be preferred, unless upstream flooding or environmental values are of concern. Such measures can be applied to catchments with either high or low soil infiltration capacity.

• Preference for large scale harvesting schemes as opposed to small (eg allotment) to medium sized (eg local reserve) schemes, although on-site harvesting using rainwater tanks should not necessarily be discouraged.

• For catchments with moderate to high soil infiltration capacity allotment level raingardens for new developments could be promoted as well as catchment scale infiltration basins, or minor road infiltration devices. These will typically provide benefits with regards to flooding and some water quality benefits.


Assess short-listed measures and review for quality, flooding, harvesting/re-use, economic and social.

Select strategy(s) according to multi-criteria analysis outcomes.

Undertake a multi-criteria analysis that includes a ranking procedure that considers objectives and analysis outputs.

Identify and short-list preliminary WSUD measures for assessment.

Determine and rank key objectives for the catchment.




• For catchment with low soil infiltration capacity minor road streetscape filtration systems such as bioretention pods could be applied strategically across the catchment, particularly in areas where flooding is of concern, or where contaminant loads are highest (eg industrial and commercial areas). These could also provide traffic calming benefits.

• Minor road infiltration/filtration devices would typically be preferred over minor roadside swales (provided sediment loads are not excessive).

• Major road bioretention devices in medians would not be considered practical due to costs and disruptions during road reconstruction. In fact retrofitting would require complete reconstruction of the road to enable drainage to the central median. Such works would be enormously expensive, and practically very difficult due to services etc. Road side devices such as permeable pavements would be preferred.

• On-site detention tanks would only be considered as a final option, if no other measures are applicable.



6 REFERENCES Argue, J., Allen, M., Geiger, W., Johnston, J., Pezzaniti, D., Scott, P., (2004). “Water Sensitive Urban Design: Basic Procedures for Source Control of Stormwater – A Handbook for Australian Practice”. First Edition. Ferderick, R., Goo, R., Corrigan, M., Barlow, S., and Billingsley, M., (2001). “Economic Benefits of Urban Runoff Controls”. Cited in Taylor (2005). Fletcher, T.; Duncan, H.; Lloyd, S. and Poelsma, P. (2005). “Stormwater Flow and Quality and the Effectiveness of Non-proprietary Stormwater Treatment Measures”. Technical report 04/8. Co-operative Research Centre for Catchment Hydrology, Melbourne, Victoria. KBR (2004). “Metropolitan Adelaide Stormwater Management Study Part A – Audit of Existing Information Final Report”. Prepared by Kellogg Brown and Root Pty Ltd for the Metropolitan Adelaide Stormwater Management Steering Committee. KBR (2004). “Metropolitan Adelaide Stormwater Management Study Part B –Stormwater Harvesting and Use Final Report”. Prepared by Kellogg Brown and Root Pty Ltd for the Metropolitan Adelaide Stormwater Management Steering Committee. Lloyd, SD., Wong, HF., and Chesterfield, CJ., (2002). “Water Sensitive Urban Design – A Stormwater Management Perspective”. Industry report 02/10, September 2002, Cooperative Research Centre for Catchment Hydrology, Melbourne, Victoria. Cited in Taylor (2005). Lloyd, SD., (2004). “Quantifying Environmental Benefits, Economic Outcomes and Community Support for Water Sensitive Urban Design”. Cited in Taylor (2005). Pezzaniti, D. (2003). “Drainage System Benefits of Catchment Wide Use of Rainwater Tanks”. Report prepared for the Department of Environment and Heritage Water Conservation Partnership Project. Still, D. and Bewsher D. (1999). “On-site Stormwater Detention in the Upper parramatta Catchment – Lessons for all Councils”. Stormwater Industy Association workshop, 15 June 1999, Concord Function Centre. Taylor, A. (2005). “Guidelines for Evaluating the Financial, Ecological and Social aspects of Urban Stormwater Management Measures to Improve Waterway Health”. Cooperative Research Centre for Catchment Hydrology. Technical Report 05/11. TCWMB (2002). “2002-2007 Catchment Water Management Plan”. Prepared by the Torrens Catchment Water Management Board.



Tonkin (2003). “Meakin Terrace Catchment – Initial Urban Stormwater Master Plan”. Prepared by Tonkin Consulting for the City of Charles Sturt. US EPA (2001). “Conceptual Measures of Economic Benefits”. Cited in Taylor (2005). USIEG (2005). “Urban Stormwater Management Policy for South Australia”. Prepared by the Urban Stormwater Initiative Executive Group. UWRC (2005). “Stormwater Detention Evaluation Project – Field Survey Final Report”. Prepared for the Campbelltown City Council, South Australia. UWRC (2006). “Stormwater Detention Evaluation Project – Stormwater Modelling Final Report”. Prepared for the Campbelltown City Council, South Australia. West, S.; Pezzaniti, D. (2005). “Water Sensitive Urban Design: Limitations and Opportunities within a Typical Urban Streetscape”. Prepared for the University of South Australia. Civil Engineering investigation project.


Urban Water Resources Centre, University of South Australia Page A.1

APPENDIX A

Water Sensitive Urban Design: Limitations and Opportunities within a Typical Urban Streetscape

Samantha West and David Pezzaniti University of South Australia

Abstract

An investigation was undertaken to determine how WSUD methods and approaches could be implemented into a typical urban streetscape, with consideration given to infrastructure and underground services. A number of typical streetscapes, from different catchments, were chosen for detailed analysis. Cross sections were drawn, from construction plans, to illustrate the distribution of services and infrastructure of these streets. A comparative analysis was carried out to determine the most feasible options within different streetscapes. Major roads have limited opportunity to implement WSUD systems due to the extensive number of services and infrastructure and limited availability of pervious areas. The main scope for inclusion of WSUD in major roads appears to be within the median strip, when available. Minor roads in older areas were found to be most suitable for above surface applications due to the wide verges available. Minor roads in newer areas were found to be most suitable for below ground applications due to high density development, higher number of driveway crossings and narrower verges. There is little opportunity to implement WSUD systems within an established site, without redevelopment of the streetscape.

A.1 Introduction Water sensitive urban design (WSUD) is a sustainable stormwater management approach to assist local governments with the pressures of urbanization on the environment and water supply. It aims to control the quantity and improve the quality of runoff and also to conserve rainwater for domestic and commercial use. An investigation was undertaken to determine the limitations and opportunities for implementing WSUD systems within an urban streetscape. The streetscape features that were taken into account include underground services, infrastructure and the road layout and design. An analyses of three catchments that are representative of those experiencing urbanization pressures on their stormwater infrastructure and receiving water environments was carried out. These catchments include the Trimmer Parade catchment, Stonyfell Creek catchment and the new Gawler sub-division (McKinlay Ridge). A number of road streetscapes were selected from



the three catchments for detailed analysis. The limitations and opportunities of implementing WSUD systems within these streetscapes were determined and a comparative analysis was carried out to determine the most feasible options for different types of streetscapes. The analysis lead to several concepts that were considered to be to the most effective WSUD measures and strategies for local government agencies to implement into their development plans.

A.2 Catchment Description The investigation was based on typical urban developments in South Australia, with conventional stormwater conveyance management systems. Two older developments and one new development were analysed. The Trimmer Parade catchment, within the City of Charles Sturt; part of the Stonyfell Creek catchment, within the City of Burnside; and a new subdivision within the City of Gawler were found to be appropriate study areas for this investigation.

A.2.1 Trimmer Parade Catchment

The Trimmer Parade catchment has a total area of 426ha and consists of a medium to high density urban development (approximately 15 residences/ha) as defined by Argue 1986. Stormwater runoff is managed by a conventional pipe drainage network. The slope of the catchment is very flat and flows in the westerly direction. Due to the considerably flat slope of the land, the drainage network has a low capacity. For this reason the Trimmer Parade Catchment is prone to flooding. The soil types within the Trimmer Parade catchment are characterised as low reactivity and moderate to high hydraulic conductivity. With these characteristics, the soil types are considered suitable for the implementation of infiltration devices as a means of stormwater management (Tonkin, 2003).

A.2.2 Stonyfell Creek Catchment

The Stonyfell Creek catchment has a total area of 367ha and consists predominately of high density urban development (approximately 20 residences/ha) as defined by Argue 1986. Stormwater is managed by a conventional pipe drainage network. The overall slope of the catchment is moderate to steep and is generally to the north-west. The soil types within the Stonyfell Creek catchment are characterised by significant reactivity to changes in moisture content and low permeability.



A.2.3 New Gawler Sub-division (McKinlay Ridge)

The new McKinlay Ridge sub-division is a high density urban development (approximately 20 residences/ha) as defined by Argue 1986, with some reserves distributed throughout. Stormwater runoff is managed by a conventional pipe drainage network. The slope of the catchment is considerably steep and is generally to the south. The soil type has medium to high reactivity with changes in moisture content (Barnes 2000).

A.2.4 Specific Study Areas within Each Catchment

This investigation looks at the limitations and opportunities within a number of roads from each catchment, which are representative of the general catchment characteristics. The streets chosen from the Trimmer Parade catchment are Trimmer Parade and Hallville Street. The streets chosen from the Stonyfell Creek catchment are Portrush Road, between The Parade and Magill Road, Tusmore Avenue and Coolibah Avenue. The streets chosen from the McKinlay Ridge sub-division are Corella Avenue, Teal Court and Falcon Drive.

A.3 Typical Urban Streetscapes The cross sections of a typical urban minor road and a typical urban major road are illustrated in Figure A.1 and Figure A.2, respectively. The road reserve widths are typically 15 m for a minor road and 30 m for a major road. The road pavement widths are typically 7.6 m wide for a minor road and 20-25 m for a major road.

The road is crowned in the middle to allow stormwater drainage to each side. Major road pavements usually include a median strip. Verge widths are typically 3-4 m for a minor road and vary for a major road, depending on space limitations. Verge widths are normally minimal for a major road.

Streetscape features for both minor and major roads include footpaths, driveways, kerb and gutters, streetlights, bus shelters, seats, post boxes, vegetation, tree guards, street signs, bollards, litter bins and fences (L.G.A 1997). Services include:

Common service trench, located beneath the verge surface on either or both sides of the road. Space within the trench is allocated for telephone, gas and electricity services.

Water main, located on either side of the road and is situated approximately 800 mm beneath the surface of the road pavement and approximately 1600 mm inside the kerb and gutter.

Sewer, located 1500 mm or greater beneath the centre of the road pavement.



Stormwater pipe, located beneath the kerb and gutter on either side of the road. Stormwater pipes have a wide range of sizes, which are designed for a particular ARI event. Standard sizes range from 100 mm to 1800 mm diameter. Box culverts are also available in specified sizes.

Figure A.1 Typical minor road cross section

Figure A.2 Typical major road cross section



A.4 Limitations and Opportunities within Streetscapes Each of the selected steetscapes were assessed for potential opportunities and limitations of implementing WSUD systems based on physical aspects. An overview of each street and the investigation results are provided below.

A.4.1 Portrush Road

Portrush Road is a major road located within the suburbs of Beulah Park and Kensington. This investigation assesses part of Portrush Road between The Parade and Magill Road. Two sections were analysed and both show a number of services underground. The services extend across the full width of the road reserve. The road pavement is wide, which leaves only a small verge, on both sides of the road, for footpaths. The cross sections are generally the same except one is located at the top of the catchment and does not have a wide median strip. Limitations

The limitations that were identified for Portrush Road includes systems that involve infiltration and require significant area. For this reason WSUD systems that are not suitable include; leaky wells, extended detention basins, wet detention basins, sediment basins, retention trenches, infiltration basins, swales and filter strips. Opportunities

The opportunities found to be suitable for Portrush Road include permeable paving within the parking bay zone and a bioretention swale, retention trench or infiltration basin within the median strip. A perforated pipe draining the filtered runoff from permeable paving could be connected to the main stormwater drain. The common service trench is the only service that may be affected by the implementation of the permeable paving. Figure 4.1 shows typical details for the inclusion of a bioretention swale in the median strip. There would be adequate clearance from any services for all devices that could be considered in the median strip. These systems would need to be designed so that a perforated pipe receives all the infiltrated water and does not affect the moisture content of the surrounding soil. The road would require regrading towards the median strip.



Figure A.3 Portrush Road Cross Section B-B Bioretention Swale

A.4.2 Tusmore Avenue

Tusmore Avenue is a collector road, located within the suburbs of Leabrook and Hazelwood Park. Three sections of Tusmore Avenue were assessed between Rochester Street and Kensington Road. Cross section A-A is located at the downstream end of Tusmore Avenue, with the services situated primarily on the eastern side. This cross section is without a stormwater drainage pipe, as the line turns west further upstream. Cross section A-A is also characterised with standard verge widths, dense vegetation and a parking inlet. Cross section B-B is located mid way along Tusmore Avenue, with the services situated primarily on the eastern side. This cross section is characterised with a large stormwater box culvert, and wide road pavement. The verges have less than standard widths. Cross section C-C is located at the upstream end of Tusmore Avenue, with the services distributed over the entire cross section. This cross section is characterised with an unusually large water main, wide pavement, standard verge widths and a footpath on the eastern side. Limitations

The limitations that were identified for Tusmore Avenue include systems that rely on infiltration and those requiring significant area. For this reason WSUD systems that are not suitable include; leaky wells, extended detention basins, wet detention basins and filter strips. Permeable paving was also considered unsuitable due to the high traffic loading. Other specific limitations include:



• There is no opportunity to implement a sediment basin or a sand filter within cross section A-A as there are no drainage pipes available. Cross section A-A is also located just after a high point in the road; therefore very little flow would be arriving at this location.

• Swales are also not feasible within cross section B-B due to the narrow verges. • There are no opportunities to implement a sand filter at cross section C-C as there are a

number of services on both sides of the road which would be affected, should a sand filter be installed.

Opportunities

The opportunities found to be suitable for cross section A-A includes; a bioretention basin, a swale, a retention trench and an infiltration basin within the verge on the western side of the road. There are no services that would be impeded upon by these systems. A perforated pipe would be required to capture all of the infiltrated water to minimise any shrinking and swelling of the soil. The road would require regrading towards the western verge to maximise runoff entering the device. Should the swale be implemented the driveways will require reconstruction to provide either an ‘at-grade’ crossing or an ‘elevated’ crossing (Brisbane City Council 2004). The opportunities found to be suitable for cross section B-B includes; a bioretention basin, a sand filter, a retention trench and an infiltration basin within the western side verge. The telephone cable on the western side may require moving. As there are no opportunities to implement any WSUD systems on the eastern side due to services, it would be practical to locate the footpath on this side. This would allow the entire verge width on the western side to be used for these systems. An impermeable liner and a perforated pipe would be required for the infiltration device and the bioretention basin to capture and transport the infiltrated water to the drainage network. The road would require regrading towards the western side of the road. The opportunities found to be suitable for cross section C-C includes; a bioretention basin, a retention trench and an infiltration basin on the western side of the road. An impermeable liner and a perforated pipe would be required due to poor soil conditions. The road would require regrading towards the western side of the road.

A.4.3 Coolibah Avenue

Coolibah Avenue is a minor road, located within the suburb of Kensington Gardens. Cross section A-A is located at the upstream end of Coolibah Avenue, with the majority of services situated on the western side. There is no stormwater pipe along this road, as the stormwater flows via the gutter into Cuthero Terrace. The verge is unusually wide for the entire length of the road and the road pavement width is slightly less than standard. This broadens the



opportunities for implementing WSUD systems. The verges contain trees and grass and the location of the footpath is unknown. Limitations

The limitations that were identified for Coolibah Avenue include; leaky wells as they rely on infiltration into the surrounding soil, extended detention basins and wet detention basins due to space limitations and sediment basins and gross pollutant traps due to low volume of pollutants. Opportunities

The opportunities found to be suitable for this road includes; bioretention basins, a swale, permeable paving, retention trenches and infiltration basins. Such devices would need to be located on the eastern side, away from services. The road pavement would require grading towards the eastern side to allow all runoff to enter these systems, including the permeable paving. Should the swale be implemented, driveways would require reconstruction to provide either an ‘at-grade’ crossing or an ‘elevated’ crossing (Brisbane City Council). An impermeable liner and a perforated pipe would be required for these systems due to poor soil conditions.

A.4.4 Trimmer Parade

Trimmer Parade is a major road located within the suburbs of Findon, Woodville West and Seaton. Cross section A-A is located at the upstream end of Trimmer Parade and shows a number of services distributed under the road pavement. Cross section B-B is located at the downstream end of Trimmer Parade and again shows a number of services distributed under the road pavement. Limitations

The limitations that were identified for Trimmer Parade include; extended detention basins, wet detention basins, sediment basins, bioretention basins, infiltration basins and filter strips due to space restrictions; leaky wells as they are more appropriate at the allotment level; permeable paving due to high traffic volume; and swales due to high density development. Opportunities

Retention trenches and infiltration basins could be implemented on either side of the road at the verges. Although cross section A-A is located at the upstream end of the road, the use of these devices would still be practical due to the considerably flat slope of the area. This device would assist in storing stormwater in a flood prone area and provide treatment. Sand filters and gross pollutant traps would also be suitable for implementation upstream of the infiltration devices.



The grass areas within the verges could be excavated to form trenches that would retain runoff from footpaths and front yards. The water would infiltrate into the ground and overflow would be directed to the street. This is an alternative solution to the implementation of bioretention basins due to space restrictions. This method would not be as effective as a bioretention basin; however it could assist in reducing peak flows in a flood prone area.

A.4.5 Hallville Street

Hallville Street is a minor road located within the suburb of Seaton. The road section is characterised by a narrow pavement and wide verges. The services are primarily on the eastern side, with the exception of the water main. A further section examined is of a roundabout located on Hallville Street. The majority of services are located beneath the roundabout, where they cross the road intersection. Limitations The limitations that were identified for Hallville Street include; extended detention basins, wet detention basins, sediment basins and filter strips due to space restrictions; leaky wells as they are more appropriate at the allotment level; and permeable paving due to the number of services under the road pavement. Also swales are not considered appropriate for the roundabout. Opportunities within Road Reserve

To convey the flow downstream, the use of swales within the verges would be suitable. There is sufficient verge width to implement a grassed or vegetated swale. The driveways will require reconstruction to provide either an ‘at-grade’ crossing or an ‘elevated’ crossing (Brisbane City Council 2004). Bioretention basins could be implemented on the western side of the road to avoid underground services. These would be located between the driveways to retain runoff and provide treatment. Infiltration basins and retention trenches could be implemented due to the rapid internal drainage of the soil. These devices would need to be implemented on the western side, to avoid services (Figure A.). Such devices would assist in storing stormwater in a flood prone area and provide treatment. Sand filters and gross pollutant traps are also suitable for implementation at the top of the treatment train. Opportunities within Roundabout

The most suitable opportunity for the roundabout would be a bioretention basin, due to its flexibility and aesthetics. The kerbing would need to be flush with the road and the basin would need to be below road level. Spoon drains would be required to direct flow from the streets to



the roundabout. Hallville Street is located in a very flat area and water does not flow efficiently. The use of basins to cater for the flow is suitable for this area to prevent flooding of adjacent properties. Locating these basins at every roundabout could reduce peak flows downstream and provide a high level of treatment. Roundabouts could be constructed at appropriate intersections for the purpose of implementing bioretention basins.

Figure A.4 Hallville Street Cross Section A-A Infiltration Basin

A.4.6 Corella Avenue

Corella Avenue is a minor road located in the new McKinlay Ridge development. The cross section is characterised by a relatively narrow road reserve, with services mainly on the eastern side.



Limitations

The limitations that were identified for Corella Avenue include; extended detention basins, wet detention basins, sediment basins and bioretention basins due to space restrictions; leaky wells due to poor drainage within the soil; retention trenches and infiltration basins due to the high construction sediment loads; swales and filter strips due to narrow verges and frequent driveways; and sand filters and gross pollutant traps due to the small catchment size. Opportunities

For the purpose of this study, it is assumed that Corella Avenue is suitable for permeable paving due to the low traffic volume. As the soil in this area has low hydraulic conductivity, infiltrated water would need to be directed to a stormwater outlet. Permeable paving structures are typically less than 1m deep and thus will not intercept with the sewer main (Figure A.). The grass areas within the verges could be excavated to form trenches that would retain runoff from footpaths and front yards. Retained water would infiltrate into the ground and overflow would be directed to the street. This is an alternative solution to the implementation of bioretention basins due to space restrictions. This method would not be as effective as a bioretention basin; however it would assist in reducing peak flows.

Figure A.5 Corella Avenue Cross Section A-A Permeable Paving



A.4.7 Teal Court

Teal Court is a minor road located in the new McKinlay Ridge development. The cross section is characterised by a relatively narrow road reserve with services distributed over the entire cross section. At the downstream end of Teal Court a recreational reserve is located on the western side. There are no services located within this reserve. Limitations within Road Reserve

The limitations that were identified for Teal Court include; extended detention basins, wet detention basins, sediment basins and bioretention basins due to space restrictions; leaky wells due to poor drainage within the soil; retention trenches and infiltration basins due to the high construction sediment loads; swales and filter strips due to narrow verges and frequent driveways; and sand filters and gross pollutant traps due to the small catchment size. Opportunities within Road Reserve

For the purpose of this study, it is assumed that Teal Court is suitable for permeable paving due to the low traffic volume. The permeable paving would be located on the northern side of the road only, to avoid services. The road would require regrading towards the north to allow all the stormwater to be directed to the permeable pavement. As the soil in this area has low hydraulic conductivity the infiltrated water would need to be directed to a stormwater outlet. The grass areas within the verges could be excavated to form trenches that would retain runoff from footpaths and front yards. The water would infiltrate into the ground and overflow would be directed to the street. This is an alternative solution to the implementation of bioretention basins, due to space restrictions. This method would not be as effective as a bioretention basin; however it would assist in reducing peak flows. Limitations within Recreational Reserve

As the reserve is for recreational use, a wet detention basin and a wetland area would not be feasible. Wet detention basins hold the water on site for long periods of time and wetlands require a large area of land. Opportunities within Recreational Reserve

An extended detention basin allows stormwater runoff to be held for a maximum of one to two days, whilst still enabling recreational use of the reserve during dry periods. This would effectively reduce peak flows downstream. Ponds could potentially be implemented into the park for recreational, ecology, retention and treatment purposes. Bioretention basins would be suitable within the park. They can be designed for a range of different shapes, sizes and vegetation to blend in with the surrounding environment. Grassed



and vegetated swales would be suitable to convey stormwater from the park to the drainage network. Bioretention swales not only convey the stormwater, they treat the runoff through fine filtration and biological uptake. If the groundwater conditions are suitable, an ASR scheme could be applied within the reserve.

A.4.8 Falcon Drive

Falcon Drive is a collector road located in the new McKinlay Ridge development. Falcon Drive is characterised with a standard road width (for a minor road) with services distributed over the entire cross section. The verge widths are considerably narrow. Limitations

The limitations that were identified for Falcon Drive include; extended detention basins, wet detention basins, sediment basins and bioretention basins due to space restrictions; leaky wells due to poor drainage within the soil; retention trenches and infiltration basins due to the high construction sediment loads; swales and filter strips due narrow verges and frequent driveways; and permeable paving due to the high traffic volume. Opportunities

There is an opportunity to implement a sand filter on the southern side of the road, above the stormwater pipe. There are no services restricting construction and sufficient space is available through subsurface installation. The sand filter would treat runoff from Corella Avenue and Falcon Drive, as the pipe network in connected between these two roads. The grass areas within the verges could be excavated to form trenches that would retain runoff from footpaths and front yards. The water would infiltrate into the ground and overflow would be directed to the street. This is an alternative solution to the implementation of bioretention basins, due to space restrictions. This method would not be as effective as a bioretention basin; however it would assist in reducing peak flows

A.5 Comparisons

A.5.1 Old and New Streetscapes

Older streetscapes tend to be characterised with wide verge widths, a number of services distributed over the width of the road reserve, large allotments, footpaths on one or both sides, streetlights and in some cases overhead powerlines. New streetscapes tend to be characterised with small verge widths, narrow streets, small front yards, small allotments, fewer services distributed over the width of the road reserve and footpaths on one side of the road. Newer



developments tend to be more consistent with the typical cross sections in terms of road layout and service locations. New developments tend to be high density areas, whereas established developments are generally medium dense with wider road reserves. Road reserves tend to be narrower in newer developments; therefore underground systems such as sand filters are more feasible for implementation. The wider road reserves, in the older areas, provide sufficient space to implement WSUD devices aboveground, such as bioretention basins. New developments have the advantage of being able to incorporate WSUD systems into the development plans. The streetscape can be designed to include WSUD measures without impeding upon services or infrastructure. Older developments would require road reconstruction for the implementation of most WSUD strategies.

A.5.2 Major Roads and Minor Roads

Major roads tend to be characterised with a wide road pavement, very little verges, median strips, bus stops, street lights, footpaths on both sides and a considerable number of services distributed across the road reserve. Minor roads are characterised with a narrow road pavement, wide verges, one footpath and fewer services. Major roads provide the opportunity to implement WSUD systems within the median strip, whereas minor roads have the opportunity to implement WSUD systems within the road verges.

A.6 CONCLUSION

A.6.1 Existing Developments

This investigation assessed a number of different streetscapes to determine the most appropriate WSUD methods and systems to implement into existing developments. Although there are a range of best management practices, the opportunities to implement these into urban streets are limited by the number of services, infrastructure and the conventional streetscape design. The analysis showed that major roads have limited opportunity to implement WSUD systems due to the minimal pervious areas and the extensive number of services and infrastructure. The main scope for inclusion of WSUD in major roads appears to be within the median strip, when available. Minor roads in older areas were found to be most suitable for above ground applications due to the wide verges available. Minor roads in newer areas were found to be most suitable for below ground applications due to high density development, higher number of



driveway crossings and narrower verges. There is little opportunity to implement WSUD systems within an established site, without redevelopment of the streetscape.

A.6.2 New Developments

Based on this investigation, some recommendations have been made as to the best streetscape cross section for implementing WSUD systems in new developments. These recommendations are outlined below:

Locate the services on one side of the road, preferably the side that the footpath is on. Only have one footpath on the side that the services are on. Slope the road away from the services. Implement WSUD systems on the side opposite the services Decide on the most appropriate WSUD option for the street to allow relevant planning

to occur. These recommendations also apply to existing developments, however reconstruction could be costly. Where redevelopment or reconstruction is occurring, in existing developments, these recommendations should be considered.

A.7 References Argue, J. 1986, Storm Drainage Design in Small Urban Catchments, Australian Road Research Board, Victoria, Australia. Barnes, G.E 2000, Soil Mechanics: Principles and Practices, 2nd edn., Palgrave, New York. Brisbane City Council 2004, Draft Water Sensitive Urban Design Engineering Guidelines, [Online, accessed 10th Sept. 2005] URL: www.healthywaterways.org Local Government Association 1997, Services in Streets a Code for the Placement of Infrastructure Services in New and Existing Streets, P.U.A.C.C, South Australia. Tonkin Engineering Science 2003, City of Charles Sturt Trimmer Parade Catchment: Initial Urban Stormwater Master Plan, South Australia.

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