Design of dykes to protect against debris flows at Port Alice, British Columbia

In 1973 and again in 1975 the town of Port Alice on Northern Vancouver Island was damaged by debris flows from the steep mountain slopes behind the town. The flows were triggered during heavy rains by small earth slumps that flowed down steep narrow gullies in bedrock and scoured additional debris from the channel. The debris flowed rapidly while confined to the gully and slowed down and came to rest on the fan on which the town is built. Dykes to protect the town from future debris flows were designed and built. Model studies were used to assist in designing the system of dykes.