Water Quality and Sediment Behaviour of the Future: Predictions for the 21st Century (Proceedings of Symposium HS2005 at IUGG2007, Perugia, July 2007). IAHS Publ. 314, 2007, 71-78

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Assessing the effects of design and climate change on sediment removal in urban stormwater ponds

catherine t. Morgan¹, kate v. Heal², steve g. Wallis¹ & rebecca j. Lunn³

1 School of the Built Environment, Heriot-Watt University, Riccarton, Edinburgh EH14 4AS, UK

2 School of GeoSciences, The University of Edinburgh, Crew Building, The King's Buildings, West Mains Road, Edinburgh EH9 3JN, UK

k.heal@ed.ac.uk

3 Department of Civil Engineering, University of Strathclyde, John Anderson Building, 107 Rottenrow, Glasgow G4 0NG, UK

Abstract Urban stormwater pond design normally only considers single storm events, does not explicitly consider climate change and is often inconsistent, with some approaches emphasising flow attenuation and others emphasising water quality enhancement. These design issues were explored for sediment removal (by settling) through modelling generic cylindrical ponds sized using current UK guidance. Results showed that ponds designed for flow attenuation had a higher sediment removal efficiency than those designed for water quality enhancement (78% vs 21% removal of incoming sediment, respectively, for the 1 in 2 year storm event). Sediment removal efficiency remained almost unchanged when multiple rather than single storm events were routed through ponds, but decreased with increasing storm event magnitude. Overall, decreased sediment removal is likely from the more frequent and intense storm events predicted due to climate change. Urban stormwater ponds designed for flow attenuation are more successful for both flow and sediment attenuation.

Key words climate change; design; modelling; ponds; retention basins; Scotland; sediment; SUDS; urban stormwater

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