A Water Sensitive Urban Design approach to mitigate the effects of Rainfall Derived Infiltration and inflow on existing sewerage systems

Coogan, Tim (2022) A Water Sensitive Urban Design approach to mitigate the effects of Rainfall Derived Infiltration and inflow on existing sewerage systems. [USQ Project]

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Urban developments can cause various detrimental impacts on public health and the environment, primarily due to the modification of the catchment and natural water cycle during rainfall events. Increases in impervious areas across catchments can cause increases in stormwater runoff volumes, discharge rates and pollution, directly resulting in sewage entering flood waters and stormwater networks exceeding their designed capacity.

This research aims to analyse and quantify the benefits of Water Sensitive Urban Design (WSUD) in an urban residential catchment and identify a relationship between WSUD in mitigating Rainfall Derived Infiltration and Inflow (RDII) in existing sewerage systems during high rainfall events. This research, also aims to identify the knowledge gap in this area and encourage further research in mitigating RDII, thus reducing the risk to public health and the environment caused by sewer overflows and sewer releases into waterways. To identify the forementioned relationship, a medium sized urban residential development was designed. Predeveloped and post developed scenarios were analysed in relation to stormwater runoff using MUSIC by eWater, (Model for Urban Stormwater Improvement Conceptualisation) and WSUD approaches were analysed to quantify their mitigating effect on RDII in an existing sewerage system. RDII was estimated for the catchment and a comparative study was created to determine the reduced amount of RDII through implementation of WSUD.

A total of five WSUD strategies were quantified including, a bioretention basin, bioretention swale, street tree pits, permeable pavements and rainwater tanks. A combination of all these strategies, in the residential development, was also investigated and found to produce the most desirable results. RDII in the existing sewerage system was found to be reduced by 0.0079L/s or 28.44L/hr and achieving a total reduction in peak flow by 81.3%, essentially returning stormwater runoff conditions back to predeveloped conditions for the urban development. The most effective individual WSUD was the bioretention basin, reducing expected RDII by 0.0068L/s or 24.48L/hr and achieving a total reduction in peak flow by 71.7% over the catchment.

Assumptions for the WSUD were made in accordance with best management practices and Water by Design guidelines and sewer infiltration and inflow rates were used that were based on previous research in this field. A lack of real-time flow monitoring data has reduced the level of accuracy for this study, although contribution towards the identified knowledge gap is evident. This study intends to promote further research in the development of mitigation strategies for reducing RDII, ultimately benefiting the community and the environment.

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Item Type: USQ Project
Item Status: Live Archive
Faculty/School / Institute/Centre: Current – Faculty of Health, Engineering and Sciences - School of Agriculture and Environmental Science (1 Jan 2022 -)
Supervisors: Baillie, Justine
Qualification: Bachelor of Engineering (Honours) (Civil)
Date Deposited: 20 Jun 2023 22:38
Last Modified: 20 Jun 2023 22:38
Uncontrolled Keywords: Water Sensitive Urban Design (WSUD); Rainfall Derived Infiltration and Inflow (RDII)
URI: https://sear.unisq.edu.au/id/eprint/51907

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