Assessing and restoring the resilience of urban stream networks

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The proposed research is motivated by the uncertainty in decision making processes faced by strategic partners in the management of urban stream networks. The basic problem is that urbanization increases the volume of surface runoff and the magnitude of peak discharges during floods. This water must be routed through stream networks that developed under much more moderate flow regimes. Widespread physical degradation and loss of ecosystem services such as clean air and water, aesthetics, and recreational and educational opportunities lead to what is called the "urban stream syndrome". Stormwater management and stream restoration are two available but limited techniques for the issue, but they often do not work as intended despite significant costs, and climate change poses a significant additional threat. The research gap we aim to address is the response of channel bed sediment to floods in urban creeks under different management scenarios. The field research will focus on three sites in the Greater Toronto Area, namely Wilket Creek, developed without stormwater management, Morningside Creek, developed with end-of-pipe stormwater management, and Ganetsekaigon Creek, slated for development in the coming decades. Ganetsekaigon Creek is currently home to a healthy population of Redside Dace, which is listed as an endangered species in Ontario. Quantifying the sedimentary response is critical for understanding ecosystem resilience in these systems because the sediments comprising the river bed are the physical habitat of the algae and benthic invertebrates that underpin the food web in aquatic and riparian ecosystems. The issues surrounding sediment supply and routing through a channel have received little attention in the practice of urban stream management and we will attempt to address this problem with innovative field work, laboratory studies on sediment dynamics, and the development of a decision making support tool through embedded research with our partners. We will also assess a new approach based on sediment supply management that has the potential to rebalance the physical stream network and restore ecosystem services.