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

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March 25, 2021 @ 12:00 pm – 1:00 pm America/Toronto Timezone
Christy Graham

STEP Webinar Series 2021

Registration is closed, please contact us at if you are interested in joining. 


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.

These 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 provided 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.

Additional Information

STEP is committed to creating an accessible experience for all participants. This webinar will be hosted over Microsoft Teams, which allows participants to enable live captions during the event. If you require assistance with this feature or a different accommodation, please email at least 7 days prior to the event.

Please note that audio and video will be recorded during this webinar. If you do not consent to being recorded, please contact us at to discuss your concerns, or do not join the session.

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This webinar is part of the STEP Water 2021 Webinar Series.