10.4122/1.1000001176 Phillips, B.C. Goyen, A.G. Lees, S.J. Improving the sustainability of on-site detention in urban catchments DTU Library, Technical University of Denmark (DTU) 2005 Drainage On-Site Detention Rainwater tanks Sustainability Urban flooding Cardno Willing (NSW) Pty. Ltd XP Software Pty Ltd Upper Parramatta River Catchment Trust en Conference full text 10.4122/1.1000001175 application/pdf 1 The upper catchment of the Parramatta River is one of the most urbanized catchments in Sydney and Australia. The Upper Parramatta River Catchment Trust (UPRCT) was established in 1989 to address the impacts of urbanization on flooding in the 110 km2 catchment. An On-Site Detention (OSD) policy was adopted by the UPRCT in November 1991 and has been applied to all new developments in the catchment since that time. The Trust has also published a detailed OSD Handbook. The fourth edition is due to be released in early 2005. Further investigations have been undertaken of an OSD system that controls site runoff in both the 1.5 year and 100 year ARI storms. These assessments also provided guidance on the appropriate modification of OSD parameters when: less than 100% of lot runoff is captured in an OSD tank ie. partial bypassing of the OSD tank; a rainwater tank is installed on a lot with dedicated airspace or without dedicated airspace. These further investigations are described and the guidance provided in the fourth edition of the UPRCT Handbook is discussed. It is concluded that the fourth edition of the UPRCT OSD Handbook will improve the sustainability of urban drainage practices in the upper Parramatta River catchment by not only preventing increased flooding in major (100 year ARI) storms but will also better control flooding in frequent (1-2 year ARI) storms thereby limiting impacts on urban waterways that are prone to erosion in more frequent storms.