Predicting Changes in the Important Characteristics of Sediment Regime in Urban Streams

(2010 – current)
Nima Zorriaseteyn (University of Melbourne)

It is widely accepted that urbanization can alter the geometry and stability of stream channels. It generally increases the frequency, duration and quantity of stormwater runoff. Larger and more frequent discharges cause downstream channels to enlarge, whether by widening, down cutting, or a combination of both.
Stormwater harvesting will help to decrease the excessive flows into waterways and morphologic changes. A simplification of channel morphology such as the loss of bars and benches due to urban stormwater runoff can be attributed to reduction in mobile sediments as transport capacity exceeds yield. At a finer scale, reduction in mobile sediments would influence on hyporheic exchange, which plays an important role in the chemical and biological functions of stream.
Often research has focused on forested and rural catchments and does not solely consider sediment dynamics within the urban environment. This work is planned to model important features of sediment regime in urban streams including mean suspended and bed load sediment movement and sediment size distribution (clay, silt, sand, gravel, pebble) and then to propose an approach to discover how patterns of hyporheic exchange flow will change through sediment regime variation.
This research will feed into Project P4 (Stream Ecology), within the Cities as Water Supply Catchments Program, which aims to determine the impact of stormwater harvesting on the hydrology and water quality of receiving waters, and to assess the subsequent ecological response.

Dr Michael Stewardson and Dr Geoff Vietz (University of Melbourne)