DEBRIS FLOW HAZARDS TRIGGERED BY SMALL EARTH DAM BREACHES IN THE OKANAGAN REGION OF BRITISH COLUMBIA

摘要

When an earth dam fails, the surge of water released through the breach may initiate a downstream debris flow. The failure of the Testalinden dam in the southern Okanagan region in June 2010 clearly demonstrated the destructive power of a debris flow triggered by the water released by a breach through a poorly maintained dam. Homes were destroyed and property was damaged with significant losses incurred. The debris flow was over one order of magnitude larger than the volume of water release by the dam. Numerous dam failures in the Okanagan region over the past 100 years show that the dam breaches were associated with late spring snowmelt. The spring freshet also saturates sediments lining creek channels below the dams. The likelihood for debris flow initiation is increased when dams are located on the edge of an upland plateau and the creek below the dam drops over a steep gradient to the main valley below. The hazard of debris flows triggered by failure of small dams deserves wider recognition by those assessing consequences of dam failure because the generated debris flow can be much larger and more destructive than a flood.