Track 2 Day 2: Friesen Amirault


How Bad Is Bad: A Novel Approach to Evaluating Geohazard Risks along Watercourses

Thursday March 26, 2020
10:00 to 10:30 a.m. (Hall F)


Diana Friesen, Town of Oakville
Heather Amirault, Stantec Consulting Ltd.


The Town of Oakville owns a significant amount of land within the valley corridors of Bronte Creek and Sixteen Mile Creek. These watercourses are confined systems within shale bedrock and high valley walls prone to erosion and instability.

The valley walls were evaluated in 2018 to prioritize sensitive and high-risk slopes for more detailed investigations. The methodology developed included site investigations, fluvial hazard assessments, and terrain and landslide hazard mapping.

Once hazards were identified, sites were further evaluated for exposure (i.e. proximity to the hazard) and consequence (i.e. value of the resource at risk), and assigned a relative risk ranking. The 10 sites with the highest ranks were identified for mitigation recommendations.

Preliminary mitigation options were conceived based on the specific site characteristics. Each site was coded with the options that best suited the site, and restrictions, if any, were identified.

The results of this study were compared to results using the standard Technical Guide -River and Stream Systems: Erosion Hazard Limit (OMNR 2002). The study presented here provided a similar outcome, but with better differentiation of high hazard sites, due largely to the increased level of detail in our methodology. The Town is using the ranked list of sites to prioritize maintenance and monitoring.

This presentation will provide an overview of the slope assessment and risk ranking methodology that was developed for the project.


Learning Objectives

1. Understand the types of hazards that can impact slope stability.

2. Understand the methodology used to evaluate and rank slope sites.

3. Understand how ranking risk sites can help communities plan.


Diana Friesen

Diana Friesen

Diana Friesen is the Water Resources Technologist for the Town of Oakville.

Diana is responsible for implementing capital projects related to stormwater and other water resources. She also manages the inventory, inspection, and monitoring programs for the town’s water resource assets, including SWM facilities, creeks, channels, and shoreline.

Diana is a Certified Engineering Technologist and holds a B.Sc., majoring in Environmental Science.

Heather Amirault

Heather Amirault

Heather Amirault is a Water Resources Engineer at Stantec Consulting Ltd.

Heather specializes in the areas of stream rehabilitation using natural channel design and geomorphic assessment. Her recent projects include the removal of two dams on Idlewood Creek for fish passage in Kitchener, ON, and restoration of Kokanee spawning areas after a large flood in Kelowna, BC.

Heather has worked on stream restoration and assessment projects across Canada and the U.S.