An inventory and risk-based prioritization of Steep Creek Fans in Alberta, Canada

Abstract

In June 2013, heavy rainfall caused flooding on most rivers in the province of Alberta, Canada, producing one of Canada’s most expensive natural disasters with about $6 billion (CDN) in damage. Flooding inundated several municipalities including downtown Calgary, the fourth-largest city in Canada. Debris flows and debris floods caused extensive highway closures and damages to development on alluvial fans. Following these events, the Government of Alberta requested an inventory of all fans intersecting municipal development, major roads and highways in Alberta. Such fans may be subject to debris flow, debris flood (mud flows), and/or flood hazards. The study area spans the entirety of the Alberta Rocky Mountains, approximately 51,000 km2 (7% of Alberta). We characterize 710 fans in terms of hazard level and presence and types of elements at risk. We statistically analyse watershed attributes to predict the dominant fan hydrogeomorphic process types. All fans under provincial jurisdiction are assigned priority ratings based on hazard levels and the presence and value of elements at risk. The prioritization is risk-based as it considers both hazards and potential consequences. Of the fans prioritized, 13% intersected parcels containing land and residential developments with an assessed value of $2.4 billion (CDN), and the remainder were crossed by roads, pipelines or transmission lines. We present the study results on an interactive, searchable web application that can support ongoing hazard and risk assessments and risk reduction planning.