Why are the Scarborough Bluffs experiencing erosion and landslides?
Landslides are caused by soil erosion. This is a natural process where wind and water cause movement of soil. Wave action against the bottom of the bluffs, washes material away, undercutting the bluff base, creating an over-steep and less stable slope. This creates the potential for landslides to develop. Heavy rains, saturated soils, and surface water runoff can also cause erosion and slope instability. Uncontrolled and concentrated drainage of stormwater over the slope and underground can also weaken and wash away soil creating conditions for landslides. Increases in severe rainfall and storm events can lead to increased levels of erosion.
Dangers & Precautions
TRCA encourages users to use extreme safety precautions in and around the Scarborough Bluffs. When getting close to a ravine or bluff slope, it is crucial to be aware of the natural hazards and risks. TRCA strongly recommends users stay on designated trails, respect fences, and follow signage. TRCA monitors slopes and shorelines using various techniques to identify areas of risk; however, landslides and slope failure can occur at any time. If you come across a hazardous erosion site, please report it to TRCA (https://trca.ca/…/erosion-risk…/report-erosion-hazard/)
Ravine and bluff property owners can also learn about erosion and how to prevent it in this brochure. (https://trcaca.s3.ca-central-1.amazonaws.com/…/Ravine…)
What is TRCA doing to address erosion and landslides?
TRCA’s Erosion Risk Management Program is focused on developing and maintaining erosion control structures to mitigate hazards. TRCA monitors known erosion hazard sites and assigns a priority ranking. This helps determine where to prioritize funding and whether detailed study, maintenance, remedial works, or further monitoring is recommended. There is a significant backlog of high-risk sites to address, which means TRCA must assess the condition of lower-risk properties on an annual basis. This information is used to track the rate of erosion and changes in risk and priority. The many shoreline stabilization structures installed along the Scarborough Bluffs play a key role protecting the slope base to ensure that long-term a stable incline will eventually be reached.
TRCA is currently in the planning phase of the Scarborough Bluffs West Environmental Assessment which will comprehensively study opportunities to improve public access and shoreline resiliency from R.C. Harris Water Treatment Plant to Bluffers Park. We expect public consultation for this study to start in late 2023 or early 2024.