Water Sensitive Urban Design Features Research Articles

Hedonic Pricing to Monetize Ecosystem Services Provided by Water Sensitive Urban Design: A Comparison of Geelong, Australia and Singapore

Water Sensitive Urban Design (WSUD) features increasingly are used for urban water management, green urban design, and improved community liveability, but relatively less data are available on the ecosystem services that WSUD provides. We used hedonic pricing, supported by qualitative surveys, in Geelong, Australia and Singapore, to evaluate benefits related to large WSUD features. For both locations there was a significant (α=0.05) inverse relationship between sale price of a residence and distance to the WSUD features. Qualitative surveys corroborated the hedonic pricing analysis, as a majority of people appreciated benefits accrued from living near WSUD features.

A Parsimonious Framework of Evaluating WSUD Features in Urban Flood Mitigation

In this study, a parsimonious framework for supporting Water Sensitive Urban Design (WSUD) was proposed to seek a tradeoff between investment of WSUD features and mitigation of urban flood damage. A two-dimensional (2D) hydrological-hydraulic simulation model, PCSWMM, was adopted to simulate the rainfall-runoff process and inundation scenarios, and the flood damages was evaluated based on inundated water depths and damage curves. The sensitivity of deploying various design features to flood control effects was also tested, which provided useful information for identifying potential design parameters (like conduit sizes and pond locations). The proposed framework was applied to a hypothetical case adapted from an urban district in the tropical region considering various WSUD features (i.e. rainwater storage pond, rain garden, and conduit upgrading). The results showed that when the gross investment of WSUD features increased from 0 to 1.19 million $, the damage cost would decrease from 4.61 to 3.41 million $; a linear relationship (with a R-square fit at 0.9) was found suitable to represent the relationship between the investment and the damage. The proposed framework is effective in helping assess the balance between mitigation of urban flood damage and adoption of WSUD features, and could be used to support urban water managers for a more science-based decision making towards flood risk management.

Stormwater constructed wetlands: A source or a sink of Campylobacter spp.

Stormwater constructed wetlands are not well characterised for their ability to remove pathogens which can pose public health risks during stormwater harvesting activities. This study investigated the behaviour of faecal indicator organism Escherichia coli (E.coli) and reference pathogen Campylobacter spp. in stormwater constructed wetlands, using a case study system located in Melbourne, Australia. Grab sampling and event-based monitoring revealed influent concentrations of E.coli were typical of other urban stormwater studies, yet Campylobacter concentrations were orders of magnitude above those urban stormwater studies used to develop the Australian Guidelines for Water Recycling, reached levels typical of raw domestic wastewater. The wetland consistently removed E.coli from stormwater (mean log removal 0.96, range 0.19-1.79), while Campylobacter spp. concentrations were often higher in outflow than inflow (mean log removal 0.05, range-0.9-1.25). These results indicate that E.coli is a poor indicator for this reference pathogen. The log reductions of both organisms also failed to meet the criteria specified for any end-use, as listed in the Australian Guidelines for Water Recycling, suggesting further treatment is required prior to harvesting. Finally, this study proposed that direct faecal deposition by waterfowl faeces was a microbial source to stormwater wetlands and that this was partly responsible for the varied microbial removal rates observed. Overall, this work validates the need for further characterisation of pathogens in raw urban stormwater, and the ability for water sensitive urban design features, such as wetlands, to remove both indicator and pathogenic microorganisms.

The microscale cooling effects of water sensitive urban design and irrigation in a suburban environment

Prolonged drought has threatened traditional potable urban water supplies in Australian cities, reducing capability to adapt to climate change and mitigate against extreme. Integrated urban water management (IUWM) approaches, such as water sensitive urban design (WSUD), reduce the reliance on centralised potable water supply systems and provide a means for retaining water in the urban environment through stormwater harvesting and reuse. This study examines the potential for WSUD to provide cooling benefits and reduce human exposure and heat stress and thermal discomfort. A high-resolution observational field campaign, measuring surface level microclimate variables and remotely sensed land surface characteristics, was conducted in a mixed residential suburb containing WSUD in Adelaide, South Australia. Clear evidence was found that WSUD features and irrigation can reduce surface temperature (T s) and air temperature (T a) and improve human thermal comfort (HTC) in urban environments. The average 3 pm T a near water bodies was found to be up to 1.8 °C cooler than the domain maximum. Cooling was broadly observed in the area 50 m downwind of lakes and wetlands. Design and placement of water bodies were found to affect their cooling effectiveness. HTC was improved by proximity to WSUD features, but shading and ventilation were also effective at improving thermal comfort. This study demonstrates that WSUD can be used to cool urban microclimates, while simultaneously achieving other environmental benefits, such as improved stream ecology and flood mitigation.

Watering our cities

Urban drainage infrastructure is generally designed to rapidly export stormwater away from the urban environment to minimize flood risk created by extensive impervious surface cover. This deficit is resolved by importing high-quality potable water for irrigation. However, cities and towns at times face water restrictions in response to drought and water scarcity. This can exacerbate heating and drying, and promote the development of unfavourable urban climates. The combination of excessive heating driven by urban development, low water availability and future climate change impacts could compromise human health and amenity for urban dwellers. This paper draws on existing literature to demonstrate the potential of Water Sensitive Urban Design (WSUD) to help improve outdoor human thermal comfort in urban areas and support Climate Sensitive Urban Design (CSUD) objectives within the Australian context. WSUD provides a mechanism for retaining water in the urban landscape through stormwater harvesting and reuse while also reducing urban temperatures through enhanced evapotranspiration and surface cooling. Research suggests that WSUD features are broadly capable of lowering temperatures and improving human thermal comfort, and when integrated with vegetation (especially trees) have potential to meet CSUD objectives. However, the degree of benefit (the intensity of cooling and improvements to human thermal comfort) depends on a multitude of factors including local environmental conditions, the design and placement of the systems, and the nature of the surrounding urban landscape. We suggest that WSUD can provide a source of water across Australian urban environments for landscape irrigation and soil moisture replenishment to maximize the urban climatic benefits of existing vegetation and green spaces. WSUD should be implemented strategically into the urban landscape, targeting areas of high heat exposure, with many distributed WSUD features at regular intervals to promote infiltration and evapotranspiration, and maintain tree health.

Linking urban water balance and energy balance models to analyse urban design options

AbstractUsing a water balance modelling framework, this paper analyses the effects of urban design on the water balance, with a focus on evapotranspiration and storm water. First, two quite different urban water balance models are compared: Aquacycle which has been calibrated for a suburban catchment in Canberra, Australia, and the single‐source urban evapotranspiration‐interception scheme (SUES), an energy‐based approach with a biophysically advanced representation of interception and evapotranspiration. A fair agreement between the two modelled estimates of evapotranspiration was significantly improved by allowing the vegetation cover (leaf area index, LAI) to vary seasonally, demonstrating the potential of SUES to quantify the links between water sensitive urban design and microclimates and the advantage of comparing the two modelling approaches. The comparison also revealed where improvements to SUES are needed, chiefly through improved estimates of vegetation cover dynamics as input to SUES, and more rigorous parameterization of the surface resistance equations using local‐scale suburban flux measurements. Second, Aquacycle is used to identify the impact of an array of water sensitive urban design features on the water balance terms. This analysis confirms the potential to passively control urban microclimate by suburban design features that maximize evapotranspiration, such as vegetated roofs. The subsequent effects on daily maximum air temperatures are estimated using an atmospheric boundary layer budget. Potential energy savings of about 2% in summer cooling are estimated from this analysis. This is a clear ‘return on investment’ of using water to maintain urban greenspace, whether as parks distributed throughout an urban area or individual gardens or vegetated roofs. Copyright © 2007 John Wiley & Sons, Ltd.

Some examples of water recycling in Australian urban environments: a step towards environmental sustainability

This paper discusses the concepts and results from two contrasting types of water recycling initiatives in Australia. The first type of initiative is a centralised scheme based on local authorities recycling sewage effluent and/or stormwater in urban areas. A new urban subdivision in Queensland (Springfield) is provided as an example of such a centralised scheme, with uses ranging from dual reticulation, to public space irrigation, to urban lakes. The importance of strong public consultation and partnership is stressed for scheme success. A second example of a centralised scheme is an upmarket subdivision in Adelaide, South Australia (Mawson Lakes), where stormwater and recycled effluent are designed to supply in excess of 70% of the community's total water requirement. Scheme success is highly probable because of the ready adoption of innovative water supply alternatives by South Australians. The other type of initiative operates at a household scale (Healthy Home) and demonstrates that reinventing old ideas using new technologies can allow urban households to become largely self reliant for their potable and non-potable water needs, at least in high rainfall coastal areas. However, the cost effectiveness of this self reliance will require a substantial change in the sharing of savings from deferred public infrastructure costs. We include for comparison an analysis by Coombes et al. for the Lower Hunter region which clearly demonstrates that adoption of water sensitive urban design features, such as rainwater tanks in new developments, is not only more cost effective than traditional infrastructure solutions, but also allows the deferral of new urban water supply dams by the order of decades. We conclude the paper with the observation that advances in incorporating externalities into water development economics, the "trickle down" effect of new distributed technologies, and the growing desire by urban communities to live within the capacity of their regional ecosystems will probably ensure that reforms in the urban water and wastewater cycles will pioneer the way to genuinely sustainable and liveable urban communities in the near future. In short, the Ecological Footprint of urban development will be substantially reduced.