The Chippewas of Nawash First Nation is located on the Bruce Peninsula, approximately 60 kilometres north of Owen Sound, Ontario. In October 2016, the area experienced heavy rainfall which caused serious flooding, resulting in washouts and erosion that impacted the roads and drainage systems. Resulting temporary and permanent road closures restricted access and impacted the community for several days.
The community sought a holistic drainage review of the area to identify necessary culvert repairs, ditching improvements, and channel alignment modifications to better match the natural flow paths of existing streams, minimize erosion, and improve surface drainage. The First Nation engaged Associated Engineering to provide the drainage review and engineering services for design and construction.
Climate change analysis indicated that rainfall intensities in the area could increase 8% in the next 50 years
Project Manager, Anna Comerton, tells us, “The first step of the analysis included delineating and characterizing the culvert watersheds using a combination of digital elevation models and GIS tools. Using this information, a hydrological assessment was performed using three runoff estimation methods. A hydraulic analysis was subsequently undertaken to evaluate the capacity and performance of the existing culverts, as well as identify alternative design solutions.”
Angela Peck, Hydrological/Hydraulics Analysis Lead, says, “This evaluation included a climate change sensitivity analysis which revealed that rainfall intensities may increase 8% over the 50-year design service period, impacting the sizing of the two major culverts.” The climate change sensitivity analysis was completed using the Ontario Ministry of Transportation intensity-duration-frequency Curve Tool.
One of the major culverts discharges directly to the lake, so there are both significant fish habitat considerations, as well as impacts on the hydraulics of the proposed replacement culvert structure. Construction of improvements will adhere to the Department of Fisheries and Oceans restricted activity timing windows to protect fish and habitat.
Key personnel involved on this project include Anna Comerton, Elia Edwards, Simone Bourke, Stan Matthew, Sarvejit Nagi, Christian Concolino, and Angela Peck.
We have built a strong relationship with the First Nation through this project and are now assisting with two other community projects - a condition assessment and repairs to the elementary school and a conceptual design of their ice rink.