Debris flood risk assessment for Mosquito Creek, British Columbia, Canada

• Published in: Natural hazards (Dordrecht) Vol. 65; no. 3; pp. 1653 - 1681
• Main Authors: Jakob, Matthias, Holm, Kris, Weatherly, Hamish, Liu, Shielan, Ripley, Neil
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01-02-2013; Springer; Springer Nature B.V
• Subjects: Aquatic insects; British; British Columbia; Canada; Civil Engineering; Creeks; Culicidae; Debris; Debris flow; Dendrochronology; Detritus; Earth and Environmental Science; Earth Sciences; Earth, ocean, space; Engineering; Engineering and environment geology. Geothermics; Environmental engineering; Environmental Management; Environmental restoration; Environmental risk; Exact sciences and technology; Fires; Flood hazards; Floods; Geophysics/Geodesy; Geotechnical Engineering & Applied Earth Sciences; Hazards; Hydrogeology; Hydrology; Hydrology. Hydrogeology; Mosquitoes; Mountains; National research council; Natural Hazards; Natural hazards: prediction, damages, etc; Original Paper; Risk; Risk assessment; Risk reduction; Watershed management; Watersheds; Canada; Western Canada; British Columbia; Canada, British Columbia, Vancouver; Runout analysis; Debris floods; Hazard assessment; Debris flood modelling; Risk assessment; risk assessment; floods; models; mountains; debris flows; velocity; North America; drainage basins; depth; management; standard samples; Natural hazards; reduction; flow
• ISSN: 0921-030X; 1573-0840
• DOI: 10.1007/s11069-012-0436-6

Mosquito Creek drains a 15.5 km
2
watershed on the North Shore Mountains north of Vancouver, British Columbia, Canada, and flows through the densely urbanized District and then City of North Vancouver. Previous studies determined that the creek is subject to debris floods (hyperconcentrated flows). The National Research Council of Canada is applying multi-hazard risk assessment procedures for various regions in B.C. and chose Mosquito Creek as one of its target areas. As part of its natural hazard management plan, the District of North Vancouver (DNV) requested an assessment of debris flood hazards and associated risk to life. Using a combination of empirical methods, dendrochronology and some judgment, BGC Engineering Inc. assessed debris flood hazard extent, velocity and depth for estimated 100-, 200-, 500- and 2,500-year debris flow return periods. Based on the results from the hazard assessment, risk for individuals and groups living within the hazard area, including residential homes and a fire hall, was estimated. Compared to risk tolerance criteria accepted on an interim basis by the DNV, we estimate that societal risk exceeds tolerable standards and that individual risk exceeds tolerable standards for 10 homes. The results from the risk to loss of life study have prompted DNV to implement a series of risk reduction measures including installation of a debris containment net and watershed restoration measures.