Stream Instability in Urban Watersheds and its Role in Sediment and Nutrient Loading

Urban development, causes significant changes in flow rate patterns in stream channels within urbanizing watersheds. The increased runoff volume, and increased frequency and magnitude of peak flows resulting from urbanization can cause channel instability, commonly referred to as Urban Stream Syndrome, (Paul and Meyer, 2001; Russell et al., 2020; Walsh et al., 2005). Previous studies have noted that streams in urbanizing watersheds typically experience an increase in sediment yield from bank material sources (Walter et al., 2007; Simon and Klimetz, 2008; Hawley et al., 2020). The research documented in this thesis seeks to determine: how best to determine whether a watershed channel is actually or potentially at risk of instability; how significant the increases in sediment and phosphorus transport are in out-of-regime channels; and how best to allocate efforts to reduce excessive sediment and phosphorus transport. The research area is in Southern Ontario. Data used included field measured stream stability observations, station surveys, flow measurements and water quality sample results as well as long term records of stream flow and water quality collected by government agencies. Machine learning was used to identify models of regime width, depth and specific stream power, from readily available channel geometry data. The regime specific stream power model was used to identify in-regime and destabilized channels in several watercourses in Southern Ontario, Canada. Effects of urbanization on the hydrological flows and sediment loading were explored using records of observed hydrometric and water quality data. Flow Duration Curves (FDC) and Sediment Rating Curves (SRC) were developed for watersheds with varying levels of urbanization and corresponding changes in sediment and phosphorus loads were identified. Percent Impervious Cover (PIC) in urbanizing watersheds was identified as a key indicator of sediment and phosphorus. This study identified changes in specific stream power (ω) as an early detection metric for the urban stream syndrome. The combined effects of increased FDC and increases in the exponent of the SRC resulted in significant increases in the annual sediment and phosphorus loads in urbanizing watersheds. Stream corridor erosion was identified as the most likely source of increased sediment loading in urbanized watersheds.

Grantor dc:publisher

University of Guelph

Author dc:creator

• MacKenzie, Kevin Malcolm

Advisors dc:contributor.advisor

• Gharabaghi, Bahram
• Whiteley, Hugh
• Binns, Andrew

• regime channel
• channel stability
• machine learning
• specific stream power
• urbanization
• flow duration curve
• sediment rating curve
• land use
• urban stream syndrome
• stream restoration
• suspended sediment
• phosphorous load
• percent impervious cover
• cost–benefit analysis

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/10214/28603

OAI record oai:identifier

https://atrium.lib.uoguelph.ca/server/oai/request?verb=GetRecord&metadataPrefix=dim&identifier=oai%3Aatrium.lib.uoguelph.ca%3A10214%2F28603