John R. Argue

Figtree Place: a case study in water sensitive urban development (WSUD)

Abstract Figtree Place is a water sensitive urban redevelopment consisting of 27 residential units located in Hamilton, an inner suburb of Newcastle, NSW, Australia. The site uses rainwater tanks, infiltration trenches and a central basin where cleansed stormwater enters the unconfined aquifer for water retention and retrieval. A two-year monitoring programme for roofwater, raintanks, hot water systems and first flush pits has commenced with samples taken from these sources tested for compliance with the Australian Drinking Water Guidelines (1996). Total water saving of around 60% has been shown to be feasible as well as almost complete storm runoff retention.

An evaluation of the benefits of source control measures at the regional scale

Source control measures include rainwater tanks, infiltration trenches, grassed swales, detention basins and constructed wetlands that can be used in housing allotments and subdivisions. A methodology for evaluating the regional economic benefits due to implementation of source control measures is presented and illustrated for two case studies in the Lower Hunter and Central Coast regions of New South Wales, Australia. It is demonstrated that use of rainwater tanks to supplement mains water supply for toilet, hot water and outdoor uses can very significantly reduce demand on mains water supply. Reductions in regional water demand will enable deferment of water supply headworks augmentation, while reductions in peak mains water demand will extend the life of water supply distribution infrastructure. In addition, substantial reduction of stormwater discharge from allotments can be realised. For the Lower Hunter region with an urban population of about 450,000 it is shown that construction of new water supply headworks infrastructure can be delayed by up to 34 years. Compared with the traditional provision of mains water and stormwater disposal, the use of rainwater tanks along with other source control measures can produce present worth savings to the Lower Hunter region conservatively estimated to be up to

Detention/Retention Storages for Peak Flow Reduction in Urban Catchments: Effects of Spatial Deployment of Storages

67 million. Similar results were found for the Central Coast region.

Catchment greening using stormwater in Adelaide, South Australia

Abstract Stormwater management techniques for urban flood control have remained relatively unchanged in many practices throughout the world for most of the past 150 years. In the past 30 years, however, detention and/or retention techniques have been acknowledged as alternative approaches capable of meeting flood control objectives while providing environmental benefits and, sometimes, cost savings to developers and authorities responsible for stormwater management. In many places the use of detention and/or retention techniques has become common practice, particularly in urban catchments where open space for flood control is in short supply. This paper reports results of hydrological modelling undertaken in a hypothetical urban catchment using basic hydrographs generated by the DRAINS computer package.3 The two main aims of the modelling were 1) to explore the influence of position of retention and detention flood management elements on end-of-catchment catchment ‘peak flow’ outputs in hypothetical urban catchments, and 2) to provide clear, comparative information on the performances of the different strategies examined. The outcome from this study will not necessarily be applicable directly to all urban catchments, however it is possible that a refinement of generic flood control strategies could be developed as further related studies are undertaken in this area.

A Review of the Application of Water Sensitive Urban Design (WSUD) to Residential Development in Australia

The paper reviews the goals of stormwater management adopted in Adelaide and declares a focus on harvesting of stormwater to replace mains water in irrigating areas landscaped with grass, flower beds and shrubs. Four categories of catchments are recognised according to their levels of pollution production - roof runoff and “low”, “medium” and “high” pollution runoff surfaces. Four case study examples of systems involving appropriate treatment trains are described, each one delivering harvested stormwater suitable for irrigation. Two examples are given of large roof areas draining to gravel-filled trenches providing “passive” irrigation to grassed surfaces and two examples of runoff from ground-level surfaces supplying cleansed recharge to small aquifer storage/recovery schemes.

Towards a universal stormwater management practice for arid zone residential developments

Abstract In this paper the authors review the application of water sensitive urban design (WSUD), specifically to urban, residential development in Australia. The uptake of WSUD is discussed for 13 case studies, and it is seen that application varies from implementation of local stormwater management measures through to a more holistic approach aimed at closing the urban water cycle. However, examples of this latter type approach are rare. It is seen that while stormwater treatment trains are the most dominant application of WSUD, the issue of water use, including better use of our urban resources and reduced reliance and use of imported mains water, is not being so actively pursued.

Improving Stream Low Flow Regimes in Urbanized Catchments Using Water Sensitive Urban Design Techniques

Abstract The principal centres of research and development in stormwater management are in the Worlds temperate regions for which a wide range of best practices are already known. The article suggests a strategy for improving performance in urban flood control, pollution minimisation and stormwater harvesting in and/semi-arid regions. The basis of the approach is, firstly, systematic documentation of performances in strategic project cases — by regions — followed by integration of these into a universal best practice. A documentation matrix for stormwater management cases in Adelaide, South Australia, is described. Factors considered in the matrix include devices and treatments, development types and forms. aquifer recharge capability and soil types. The matrix will provide, progressively, vital information for planners and designers and guide researchers in the most productive use of limited monitoring resources.

A Comparative Analysis of the Characteristics of Domestic Water Use in Metropolitan Adelaide

Abstract As a catchment becomes urbanised, the natural hydrological processes are significantly altered and this leads to a deterioration of the stream’s ecological condition. Low flow characteristics of a stream are useful hydrological statistical indicators for assessing the health of an ecosystem. An investigation was carried out to assess the capacity for water sensitive urban design (WSUD) measures to maintain “natural” low flow characteristics when a catchment is urbanised. A calibrated Storm Water Management Model (SWMM) of a natural catchment in South Australia was developed using historical rainfall and stream flow data. Prior to the model calibration, the sensitivity of the SWMM parameters was assessed against hydrological responses on the low flow region of the flow duration curves (FDCs) and the deficit volumes at three selected threshold flows over the calibration period. The calibrated model was then modified to generate flow data for three selected urbanised scenarios by altering the percentage of effective impervious areas. Model resolution effects on low flow regimes were assessed to ensure spatially distributed effects did not influence the results. Two selected WSUD measures were applied to one of the urbanised scenarios and low flow characteristics were examined. Flow duration and spell duration-frequency statistics of the urbanised cases were compared against those of the natural catchment. The study revealed that urbanisation causes more frequent low flow spells during both the wet and the dry seasons. As expected, the frequencies of the low flow spells with duration up to 20 days increased dramatically due to urbanisation. Both WSUD measures were capable of achieving similar frequencies for the same “natural” spell durations. The frequency of low flow spell duration events was reduced as WSUD measures were applied to the urbanised catchment case, indicating that the low flows with WSUD measures will generally be higher than those without WSUD. For the case study catchment, WSUD infiltration measures that are capable of diverting up to half of the natural groundwater input will enable low flow characteristics to be maintained.

How reliable are inlet (hydraulic) models at representing stormwater flow

Abstract An understanding of domestic water consumption is important for planning and development purposes. This paper presents a methodology for estimating in-house and ex-house water consumption in Adelaide in the absence of detailed water use studies. Bi-annual water meter readings enable metropolitan water usage to be separated into “domestic” and “other” use categories; while monthly metropolitan water treatment plant discharges are used to divide the domestic consumption component into in-house and ex-house uses and to establish the monthly trends of ex-house demand. Average annual water demand results for in-house and ex-house uses are compared with those obtained in water use studies conducted in Perth and Melbourne. The results compare well, giving validity to the methodology applied. The study shows that average in-house water consumption for Adelaide households is 140 kL; water use outdoors is 136 kL per annum.

Water sensitive urban design: basic procedures for 'source control' of stormwater: a handbook for Australian practice

Abstract It is common practice to base storm drainage network designs on gutter inlet capture information obtained from tests on hydraulic scale models. Growing interest in collection of gross pollution at inlets (‘source control’) is leading researchers to re-visit this domain of hydraulics and to question the reliability of scale models. Results from 0.4-scale and full-size models of a gutter inlet are compared in a laboratory study. Significant differences (up to 40%) were observed in flow captured, the small-scale models showing the lower values. This has important implications for pit spacing and the economics of drainage networks. Performance variation is considered to be the consequence of differences in zones of full and transition turbulence in the two model systems. This explanation is supported by differences being lower for high-flow conditions. These findings sound a warning to those using scale hydraulic models to seek solutions to the problem of ‘at source’ containment of gross pollution.