Maheepala, S, Hewa, G.A., Myers, Baden, Pezzaniti, David and Sharma, Ashok ORCID: https://orcid.org/0000-0002-0172-5033 (2012) Towards the development of stormwater flow management targets in the Greater Adelaide Region. In: The 3rd IWA_RWHM Conference and Exhibition, 20 May 2012 - 24 May 2012, Goseong, Korea.

Abstract

In Australia, the focus of stormwater management is primarily on reducing long-term pollutant loads. In recent years, however, there has been an increased interest to move towards a flow-based stormwater management approach. The aim of the flow-based stormwater management approach is to maintain a flow regime which is important to maintain ecological integrity in urban streams. The widely accepted view in this regard is to maintain a flow regime that closely approximates the pre-development flow regime. At present, there is no nationally accepted approach for managing flow regimes in urban streams, in a manner that protects aquatic ecosystems in Australia. This paper briefly explains the approaches currently being either used or considered in different states of Australia for stormwater flow management, and reports an analysis undertaken to develop preliminary or interim targets for stormwater flow (or runoff quantity) management in the Greater Adelaide Region. The aim of the interim runoff quantity targets is to restore pre-development flow regime, with a view of minimising in-stream erosion, to reduce the transport of nutrients and sediment to the receiving waters of the Greater Adelaide Region, and protecting aquatic ecosystems from frequent small flow events. The study involved examining flow characteristics of a hypothetical catchment using rainfall, evaporation and soil characteristics relevant to the Greater Adelaide Region, for different levels of urbanisation and runoff retention from directly connected impervious areas. The annual runoff volume, the flow duration curve and peak flows of a 1.5 year ARI were used to assess the effectiveness of retaining different volumes of runoff from directly connected impervious areas, in order to restore pre-development flow condition. The study suggests that for catchments with a total impervious area up to 20%, the retention (or capture) of runoff equivalent to the volume generated from 5 mm of rainfall on directly connected impervious areas is required, to reduce both in-stream erosion and frequent small flow events to a level close to the pre-development condition in the Greater Adelaide Region. For catchments with a total impervious area of greater than 20%, capture of runoff must be increased to 10 mm to achieve the same outcome.

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