Global sediment yields from urban and urbanizing watersheds
Project Engineer Kathy Russell, along with her supervisors Geoff Vietz and Tim Fletcher (University of Melbourne), has published the first output of her PhD project, a journal article titled “Global sediment yields from urban and urbanizing watersheds“. Kathy is undertaking a PhD in geomorphology while working part-time at Water Technology. Her project is aimed at understanding the sediment regime of urban streams, and how changes to sediment supply and transport might constrain the protection and recovery of streams for catchment urbanisation impacts.
The journal article, in Earth-Science Reviews, uses quantitative evidence from the international body of published literature to test a long-established conceptual model of sediment yields in urbanizing and urban watersheds. In our increasingly urban society, changes to watershed sediment yields are a key driver of urban stream degradation, which is a global yet poorly-understood problem costing billions of dollars and impacting on quality of life and biodiversity. The analysis showed that sediment yields from established urban watersheds are likely to remain higher than background yields, in contrast to predictions from the widely-accepted Wolman model. The updated model will inform future planning and management efforts to protect and restore urban streams, which will rely on preserving or restoring natural watershed processes, including sediment regimes.
A full-text version of the paper can be accessed for free at authors.elsevier.com until the 30th of May, 2017.
Streams with urban watersheds are almost universally subject to degradation, largely driven by changes to flow and sediment inputs from the watershed. However, the impact of urbanization on sediment yields of urban watersheds is poorly understood. We undertook a comprehensive review of global responses of fine-grained and coarse-grained sediment yields to different phases of urbanization and compared them to a long-standing conceptual model. The summarized yields showed a great deal of variability, but were consistent with the widely-used conceptual model for watersheds with active construction. Importantly, however, the yields for established urban areas tended to be higher than previously assumed, and tended to remain higher than background levels. This is most likely because the urban drainage network has a very high sediment transport efficiency and because the increased runoff in urban watersheds is very effective at eroding the available sediment sources (mainly infill development, urban decay and renewal, and gravel surfaces in parks and gardens). The updated model provided here will assist in informing the extent to which sediment supply to stormwater drainage systems and urban streams needs to be addressed to assist the protection and restoration of streams in urban watersheds.
Kathy is currently undertaking a field study of bedload sediment availability in urban streams, due for completion in late 2017.
If you would like to know more about Kathy’s research and how the findings could be applied to your catchment please call Kathy on +61 3 8526 0800.