Implementation Of Water Sensitive Urban Design Research Articles

Water Sensitive Urban Design (WSUD) Spatial Prioritisation through Global Sensitivity Analysis for Effective Urban Pluvial Flood Mitigation

Water Sensitive Urban Design (WSUD) has attracted growing attention as a sustainable approach for mitigating pluvial flooding (also known as flash flooding), which is expected to increase in frequency and intensity under the impacts of climate change and urbanisation. However, spatial planning of WSUD is not an easy task, not only due to the complex urban environment, but also the fact that not all locations in the catchment are equally effective for flood mitigation. In this study, we developed a new WSUD spatial prioritisation framework that applies global sensitivity analysis (GSA) to identify priority subcatchments where WSUD implementation will be most effective for flood mitigation. For the first time, the complex impact of WSUD locations on catchment flood volume can be assessed, and the GSA in hydrological modelling is adopted for applications in WSUD spatial planning. The framework uses a spatial WSUD planning model, the Urban Biophysical Environments and Technologies Simulator (UrbanBEATS), to generate a grid-based spatial representation of catchment, and an urban drainage model, the U.S. EPA Storm Water Management Model (SWMM), to simulate catchment flooding. The effective imperviousness of all subcatchments was varied simultaneously in the GSA to mimic the effect of WSUD implementation and future developments. Priority subcatchments were identified based on their influence on catchment flooding computed through the GSA. The method was tested for an urbanised catchment in Sydney, Australia. We found that high priority subcatchments were clustering in the upstream and midstream of the main drainage network, with a few distributed close to the catchment outlets. Rainfall frequency, subcatchment characteristics, and pipe network configuration were found to be important factors determining the influence of changes in different subcatchments on catchment flooding. The effectiveness of the framework in identifying influential subcatchments was validated by comparing the effect of removing 6% of the Sydney catchment's effective impervious area under four WSUD spatial distribution scenarios. Our results showed that WSUD implementation in high priority subcatchments consistently achieved the largest flood volume reduction (3.5-31.3% for 1% AEP to 50% AEP storms), followed by medium priority subcatchments (3.1-21.3%) and catchment-wide implementation (2.9-22.1%) under most design storms. Overall, we have demonstrated that the proposed method can be useful for maximising WSUD flood mitigation potential through identifying and targeting the most effective locations.

Urban household uptake of water sensitive urban design source control measures: an exploratory comparative survey across Cape Town and Pretoria, South Africa

ABSTRACT Water Sensitive Urban Design (WSUD) presents a process towards the objective of a water-sensitive city. An integrated approach requires community acceptance to implement WSUD at household level. An exploratory comparative survey was conducted amongst 250 households across Cape Town and Pretoria, South Africa, to determine actual uptake of rainwater harvesting, greywater recycling systems and permeable paving, factors affecting uptake, and the perceived effectiveness of assistance to implement WSUD relative to other water demand-side management instruments. Actual uptake of rainwater harvesting and greywater reuse is noticeable amongst water-saving middle-to-high income home owners. Although loglinear analyses suggest that Cape Town’s recent drought is unlikely to contribute towards more established levels of uptake, assistance to implement WSUD is nevertheless perceived as the second most effective instrument. Three directions for more systematic research are proposed to better inform the practical implementation of WSUD at household level.

A spatial planning-support system for generating decentralised urban stormwater management schemes

Current Water Sensitive Urban Design (WSUD) models are either purely technical or overly simplified, lacking consideration of urban planning and stakeholder preferences to adequately support stakeholders. We developed the Urban Biophysical Environments and Technologies Simulator (UrbanBEATS), which integrates stormwater management with urban planning to support the design and implementation of WSUD. This study specifically describes and tests UrbanBEATS' WSUD Planning Module, which combines spatial analysis, infrastructure design, preference elicitation and Monte Carlo methods to generate feasible stormwater management and harvesting infrastructure options in greenfield and existing urban environments. By applying UrbanBEATS to a real-world greenfield development case study in Melbourne, Australia (with data sourced from the project's water management plans and design consultants), we explore the variety of options generated by the model and analyse them collectively to demonstrate that UrbanBEATS can design similar WSUD systems (e.g. select suitable technology types, their sizes and locations) to actual infrastructure choices.

A planning-support tool for spatial suitability assessment of green urban stormwater infrastructure

Distributed green stormwater management infrastructure is increasingly applied worldwide to counter the negative impacts of urbanisation and climate change, while providing a range of benefits related to ecosystem services. They are known as Water Sensitive Urban Design (WSUD) in Australia, Nature Based Solutions (NBS) in Europe, Low Impact Development (LID) in the USA, and Sponge City systems in China. Urban planning for WSUD has been ad-hoc, lacking strategy and resulting in sub-optimal outcomes. The purpose of this study is to help improve strategic WSUD planning and placement through the development of a Planning Support System. This paper presents the development of Spatial Suitability ANalysis TOol (SSANTO), a rapid GIS-based Multi-Criteria Decision Analysis tool using a flexible mix of techniques to map suitability for WSUD assets across urban areas. SSANTO applies a novel WSUD suitability framework, which conceptualises spatial suitability for WSUD implementation from two perspectives: ‘Needs’ and ‘Opportunities’ for WSUD. It combines biophysical as well as socio-economic, planning and governance criteria (‘Opportunities’) with criteria relating to ecosystem services (‘Needs’). Testing SSANTO through comparing its results to work done by a WSUD consultancy successfully verified its algorithms and demonstrated its capability to reflect and potentially enhance the outcomes of planning processes. Manual GIS based suitability analysis is time and resource intensive. Through its rapid suitability analysis, SSANTO facilitates iterative spatial analysis for exploration of scenarios and stakeholder preferences. It thus facilitates collaborative planning and deeper understanding of the relationship between diverse and complex urban contexts and urban planning outcomes for WSUD.

Assessment of Tangible Direct Flood Damage Using a Spatial Analysis Approach under the Effects of Climate Change: Case Study in an Urban Watershed in Hanoi, Vietnam

Due to climate change, the frequency and intensity of Hydro-Meteorological disasters, such as floods, are increasing. Therefore, the main purpose of this work is to assess tangible future flood damage in the urban watershed of the To Lich River in Hanoi, Vietnam. An approach based on spatial analysis, which requires the integration of several types of data related to flood characteristics that include depth, in particular, land-use classes, property values, and damage rates, is applied for the analysis. To simulate the future scenarios of flooding, the effects of climate change and land-use changes are estimated for 2030. Additionally, two scenarios based on the implementation of flood control measures are analyzed to demonstrate the effect of adaptation strategies. The findings show that climate change combined with the expansion of built-up areas increases the vulnerability of urban areas to flooding and economic damage. The results also reveal that the impacts of climate change will increase the total damage from floods by 26%. However, appropriate flood mitigation will be helpful in reducing the impacts of losses from floods by approximately 8% with the restoration of lakes and by approximately 29% with the implementation of water-sensitive urban design (WSUD). This study will be useful in helping to identify and map flood-prone areas at local and regional scales, which can lead to the detection and prioritization of exposed areas for appropriate countermeasures in a timely manner. In addition, the quantification of flood damage can be an important indicator to enhance the awareness of local decision-makers on improving the efficiency of regional flood risk reduction strategies.

Effects of changing rainfall patterns on WSUD in Australia

Bioretention basins and permeable pavements are two widely implemented water sensitive urban design (WSUD) technologies. While their applications are extensive, their effectiveness as a result of changes in rainfall patterns is an emerging and important research question. This paper describes how these systems behave under varying rainfall conditions in Australian cities. To illustrate this, two design parameters, namely emptying times for permeable pavements and scour velocities for bioretention systems, were investigated. The study revealed that there are two groups of cities displaying almost similar peak flow characteristics – high (Darwin, Cairns, Brisbane, Townsville and Sydney) and low (Alice Springs, Hobart, Melbourne, Perth and Adelaide). It was shown that selection of an optimal storage size to ensure appropriate emptying times for permeable pavements requires a balance between managing dry periods, reuse demand and economic considerations. Increase of high flows increases the risk of scouring in bioretention basins, which is particularly significant for the first group of cities. Finally, the paper describes the importance of peak flow estimation method and appropriate selection of modelling time step for sustainable implementation of WSUD in Australia.

Understanding the nature of publics and local policy commitment to Water Sensitive Urban Design

Water Sensitive Urban Design (WSUD) is a recent planning and design philosophy in Australia primarily used to minimise the hydrological impacts of urban development on the surrounding environment. As local governments plan and regulate the bulk of public and private infrastructure and development, they are key participants in the implementation of WSUD. However, according to research conducted involving 38 municipalities in Melbourne, Australia, the implementation of WSUD is inconsistent across the metropolitan area. The mixed methods research comprised a survey of municipal officers, interviews with the officers and mayors, and a review of municipal accountability documents. The results revealed a strong municipal commitment to WSUD in areas bounded by the coast or where the natural vegetation exceeds 50% of the municipal area. Furthermore, these committed municipalities tended to coincide with communities of higher wealth and population. Overall, the analysis revealed three types of municipalities – high, partial, and limited commitment – that are indicated by a variation in environmental values, demographic and socio-economic status, local organised environmentalism, municipal environmental messages, and intergovernmental disposition. This paper argues for policy reform for WSUD, as it is largely sympathetic to the highly committed municipalities, and highlights the need to enable the participation of publics in the municipalities of limited and partial commitment by linking WSUD to greater public concerns and building commitment through diverse policy interventions.

Drainage Network Modelling for Water‐Sensitive Urban Design

AbstractWhile drainage network models may be relatively easy to assemble as a prerequisite to site selection for infrastructure supporting suburbanisation with Water‐Sensitive Urban Design (WSUD), this is unlikely to be the case if the terrain is very subdued. Both ab initio and retro‐fit WSUD implementation for such terrain refers, in the first instance, to a drainage network model that includes information on the scope for optimising residential space while conforming to: (1) statutory planning rules about the provision of public open space; and (2) WSUD drainage network design such that runoff waters are retained long enough to allow at least temporary storage. It is shown in this research that a technique applied to condition a LiDAR DEM can accurately model the drainage network of a basin at the land‐parcel scale. The drainage network for ab initio WSUD is best defined using multi‐flow modelling, with the relative significance of stream segments indicated by their stream order derived using the Strahler method. In contrast, when applying the retro‐fit WSUD, the relative significance of segments given by the Shreve stream order method was found to be more useful. The approaches described in this article are designed to support the initial site planning stage and avoid the need for immediate and expensive detailed field survey. At the same time they can be deployed to show how much scope there is for WSUD retro‐fit in established housing areas up‐stream of an infill development area. Thus, basin‐wide appraisal is facilitated and the need for earthmoving is minimised.

Impediments and Solutions to Sustainable, Watershed-Scale Urban Stormwater Management: Lessons from Australia and the United States

In urban and suburban areas, stormwater runoff is a primary stressor on surface waters. Conventional urban stormwater drainage systems often route runoff directly to streams and rivers, thus exacerbating pollutant inputs and hydrologic disturbance, and resulting in the degradation of ecosystem structure and function. Decentralized stormwater management tools, such as low impact development (LID) or water sensitive urban design (WSUD), may offer a more sustainable solution to stormwater management if implemented at a watershed scale. These tools are designed to pond, infiltrate, and harvest water at the source, encouraging evaporation, evapotranspiration, groundwater recharge, and re-use of stormwater. While there are numerous demonstrations of WSUD practices, there are few examples of widespread implementation at a watershed scale with the explicit objective of protecting or restoring a receiving stream. This article identifies seven major impediments to sustainable urban stormwater management: (1) uncertainties in performance and cost, (2) insufficient engineering standards and guidelines, (3) fragmented responsibilities, (4) lack of institutional capacity, (5) lack of legislative mandate, (6) lack of funding and effective market incentives, and (7) resistance to change. By comparing experiences from Australia and the United States, two developed countries with existing conventional stormwater infrastructure and escalating stream ecosystem degradation, we highlight challenges facing sustainable urban stormwater management and offer several examples of successful, regional WSUD implementation. We conclude by identifying solutions to each of the seven impediments that, when employed separately or in combination, should encourage widespread implementation of WSUD with watershed-based goals to protect human health and safety, and stream ecosystems.