Modeling debris flow hazards for safer zoning

Cowichan Lake North Shore Debris Flow Runout Model

The steep north shore of Cowichan Lake, part of the Cowichan Valley Regional District (CVRD), is home to approximately 1,700 people exposed to varying degrees of debris flow hazards from adjacent slopes. A prior hazard assessment had identified 462 historical landslides in the broader region and led to a recommendation for landslide runout modeling for debris flows and slides to better understand the hazard. CVRD reached out to us to help.

Our team used DebrisFlow Predictor to estimate the extent of debris flow hazards to residents and properties along the north shore. After modeling over 70,000 debris flows in the area, the results defined a credible runout limit of debris flow hazards. We identified properties within and beyond that limit, then provided estimated landslide depths (and, therefore, destructive potential) for properties within the potential runout zone.

CVRD used these results to modify zoning bylaws and identify areas requiring additional geotechnical studies.