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Using Water-Sensitive Urban Design to improve drainage capacity : Examination of the impact of distributed and catchment scale Water-Sensitive Urban Design systems on flow frequency

Noordhoek, Robin (2014) Using Water-Sensitive Urban Design to improve drainage capacity : Examination of the impact of distributed and catchment scale Water-Sensitive Urban Design systems on flow frequency.

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Abstract:Commissioned by the Centre for Water Management and Reuse, located in Adelaide, South Australia, this research was carried out to examine the impact of distributed and catchment scale Water-Sensitive Urban Design systems on runoff flow frequency. Currently, Greater Adelaide’s water supply for drinking and non-drinking purposes falls short of the demand. This shortfall will only increase in the future due to rising demand and diminishing resources if the South Australian Government does not undertake action. Also, the ratio of infill to fringe development for new housing will shift to a more infill-orientated ratio in Adelaide. This increased dwelling intensity poses challenges to infrastructure in the existing urban environment of the Greater Adelaide region. Amongst other things, this means that metropolitan catchment areas where infill development takes place will be likely to experience changes in stormwater runoff flow regimes. One of those areas is the Frederick Street catchment, a 44.7-Ha urban catchment which is the study area of this report. Building a new drainage system for the entire catchment is an expensive and time-consuming solution which will also cause a lot of nuisance. This is why alternative approaches are being taken into consideration. Water Sensitive Urban Design seems a promising solution to the problem. Therefore, it has to be investigated if Water-Sensitive Urban Design can be applied in the catchment area in order to reduce the effects caused by infill development on flow frequency. The research can contribute to the understanding of the impact of infill development on a medium sized urban catchment. It is important to understand the impact of infill development and how to overcome these impacts with WSUD tools. This might lead to sustainable solutions which do not involve drastic and costly adjustments to urban drainage systems. The objective of the project is to determine suitable WSUD measures for the catchment by producing an updated version of the catchment model using flow data being collected since August 2013. The existing model was updated and then calibrated. When the model was calibrated, the use of several suitable WSUD measures were simulated on the catchment to view their effect on flow frequency. The results of the simulation show that the total volume of runoff increases by 12% (and an average increase of 11% in peak flows) if no action is undertaken. The use of rainwater tanks and/or bioretention systems within the catchment can be effective to maintain the current flow levels, or even decrease the runoff flows and volumes. It was found that Water-Sensitive Urban Design can be used to preserve the existing flow regimes of the Frederick Street catchment. For street scale WSUD measures, rainwater tanks and bioretention systems are showing promising simulation results for reducing runoff volumes and peak flows. The most effective way of reducing runoff volumes seems to be the installation of rainwater tanks. Peak flow reduction on the other hand can be achieved by both rainwater tanks and bioretention basins. Although bioretention basins achieve a higher overall reduction of peak flows, it should be noted that for very extreme storm events they are not capable of significant peak flow reduction. Therefore a mix of both small rainwater tanks for all houses and bioretention basins seems to be the best option for preserving the flow regimes in the Frederick Street catchment. Another option, which does not need the construction of bioretention basins is to connect every house in the catchment to a bigger (e.g. 5 kL) rainwater tank.
Item Type:Essay (Bachelor)
Faculty:ET: Engineering Technology
Subject:56 civil engineering
Programme:Civil Engineering BSc (56952)
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