Improving stream health in urban areas by reducing runoff frequency from impervious surfaces

Abstract

In urbanised catchments, the frequent direct delivery of water and pollutants from impervious surfaces to streams has a detrimental effect on stream health. Recent studies of a range of ecological indicators have shown that where there is opportunity for attenuation of these inputs, that is, where the link between impervious surfaces and streams is less direct, the damage to stream health may be mitigated. This suggests that improving stream health, in areas subject to urbanisation, involves finding ways to decrease the efficiency of water delivery from impervious surfaces. We have undertaken a feasibility study to examine options to reduce the area of impervious surfaces that are directly connected to waterways by efficient drainage systems. These options include: rainwater tanks where the captured water is used to replace a portion of the mains water supply; permeable pavements that reduce runoff from roads; and swale drains and bioretention systems along roads, rather than piped drainage direct to streams. Models of the relationship between effective imperviousness and a range of ecological indicators, from previous studies, are used to assess the likely effect of these options on stream health. A large-scale experiment is now proposed to test this new approach to urban stream restoration.

Keywords:

• Urban
• watershed
• stormwater
• impervious area
• drainage connection
• low-impact design
• water-sensitive urban design
• retrofit
• ecological restoration

Additional information

Notes on contributors

A R Ladson

Tony Ladson is a senior lecturer in the Department of Civil Engineering and a member of the Institute for Sustainable Water Resources at Monash University. He is also an honorary fellow in the School of Anthropology, Geography and Environmental Studies at the University of Melbourne. His research interests include developing and testing methods to assess the condition of streams and approaches to their restoration. He has worked in the field of environmental flows and has a long-term interest in the management of the Barmah-Millewa Forest. Tony teaches undergraduate and post graduate courses in hydrology, hydraulics, flood management and water resources management.

C J Walsh

Chris Walsh is a senior research fellow at the Water Studies Centre, and an honorary research associate with the School of Biological Sciences, Monash University, Melbourne, funded by Melbourne Water. Chris has worked for 10 years on the ecology of streams in urban areas. The work of Chris’s group is identifying directions for stormwater management required to protect stream, lake and coastal ecosystems. He was a deputy program leader and leader of several large interdisciplinary projects with the Cooperative Research Centre for Freshwater Ecology

T D Fletcher

Tim Fletcher is Director of the Institute for Sustainable Water Resources at Monash University, and a Senior Lecturer within the Department of Civil Engineering. He was the Leader of the Urban Stormwater Quality Program within the CRC for Catchment Hydrology. Tim’s research focuses on the prediction of stormwater quality, treatment and aquatic ecosystem responses, and integration within the urban water cycle and waterway management. Tim has also held a number of senior roles in the water and waterway management industries, including Water Resources Manager with the Corangamite Catchment Management Authority and Senior Environmental Planner with Melbourne Water, and roles with Central Highlands Water. He co-chairs the UNESCO International Hydrologic Program VI project on data for integrated urban water management, and is on the Editorial Board of Urban Water.