Three Sisters Creek Debris Flood Hazard and Risk Assessment

The Town of Canmore experienced an intense three-day rainfall event in June 2013 leading to flooding, debris floods and debris flows in numerous mountain creeks located within the town. The floods and flows caused extensive damage to residential development and temporarily severed the TransCanada Highway. Canmore retained BGC to complete a forensic study and assess hazard and risk for four creeks, including Three Sisters Creek, which crosses a residential development, a golf course and a highway corridor into the town.

BGC’s hazard assessment considered the entire watershed. It included examination of basin geology and geomorphology and used techniques such as dendrochronology, radiocarbon dating and rainfall-runoff modelling to develop a relationship between the frequency and magnitude of flows. BGC modelled scenarios representative of the range of events that could occur and prepared maps showing the intensity, or destructive potential, of each scenario.

Based on the results of the hazard assessment, BGC then estimated key risks including damage to buildings and risk to persons within buildings. These results form the basis by which Canmore determines appropriate measures to reduce risk to tolerable levels.