Toronto and Region Conservation Authority

Patterson Creek Sanitary Infrastructure Protection

Decreasing erosional risk and improving aquatic habitat with natural channel design

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Patterson Creek, in Richmond Hill, Ontario, exhibits a history of anthropogenic alteration and an urbanized hydrologic regime. Sanitary infrastructure alongside and beneath the meandering watercourse is at risk from bank erosion and bed scour, respectively.

Several private properties alongside the creek are also at risk from channel encroachment. The design and implementation of channel improvements to mitigate unacceptable risks of erosion were complicated by the documented presence and sensitivities of Redside dace (Clinostomus elongatus), a federally listed Species At Risk.

Toronto and Region Conservation Authority
  • Fluvial Geomorphology
  • Aquatic Ecology
  • Terrestrial Ecology
May 2017 – September 2019

What We're Doing

Palmer was retained by Toronto and Region Conservation Authority to complete a comprehensive fluvial geomorphological assessment and ecological field updates (including a tree inventory) along the valley corridor of five reaches that contain at-risk sanitary crossings and valley wall erosion near private property. Our assessments informed development of conceptual alternatives for erosion mitigation for infrastructure and property protection at 12 sites. Preferred alternatives were determined through multi-parameter evaluation considering scored design implications for hydraulics, geomorphology, ecology, culture, and cost. Detailed design packages were prepared, with engineering support from Greck and Associates, for each preferred alternative at 10 of the 12 prioritized sites. Our team was requested to support construction inspection.

Fluvial Geomorphology

Watershed-, reach- or site-scale analysis of river behaviour for baseline characterization of sediment transport patterns, erosion risk assessment and mitigation (e.g. bioengineering) for infrastructure and property protection, and 'natural channel design' for creek realignments and habitat restoration. Past trends are used to manage risk to infrastructure and land development, as well as aquatic and riparian ecology

Aquatic Ecology

Industry-leading fisheries science consulting and aquatic services assisting in minimizing project effects on fish and complying with environmental legislation. Assessment of fish population dynamics, food web interactions, fish health and aquatic habitats amid human-induced impacts supporting monitoring, permitting and habitat compensation planning.

Terrestrial Ecology

Multi-disciplinary investigation of terrestrial ecosystems at regional, local and site-specific scale. Analysis includes species interaction with the environment and relevant sensitivities to resource and land development, as well as identification of potentially sensitive terrestrial elements such as groundwater-dependent wetlands, species at risk and critical habitat which may influence project timing and agency approvals.