Challenges in Classifying and Designing Spillway Upgrades for a Small Embankment Dam Upstream of an Urban Population

Author: Katrina Wechselberger, Violeta Martin, Egbert Scherman, Alana Shewan
Conference: CDA 2018 Annual Conference
Date: October 13-18, 2018


A 10 m high embankment dam located 4 km upstream of a populated area was assessed during its Dam Safety Review as requiring an upgrade to the spillway capacity to comply the current CDA Dam Safety Guidelines and BC Dam Safety Regulations. At normal operating levels, the Dam stores approximately 31,000 m3 of water. The Dam was completed in 1966 and has been successfully operated by the Dam Owner without incident for over 50 years as a critical part of the water distribution system, specifically the diversion and intake location for the irrigation system serving the area’s rural community. Various studies were completed on the Dam to assess its compliance and classification under the new criteria.

Due to the confined valley and orientation of the spillway weir, the only feasible solution to continue the existing
operation without decommissioning and replacement, was to raise the crest of the Dam in order to pass the new design flood through the existing spillway. Given the downstream permanent population, the inundation study showed areas of residential and commercial properties affected. A detailed study translating inundated areas into an estimated loss of life and economic losses followed. A discussion of the risk mitigation efforts and emergency planning that is possible with a forecasted flood induced event led to a solution that satisfied both the consequence criteria of the CDA Dam Safety Guidelines, the BC Dam Safety Regulations and the engineering design limitations for this small dam and reservoir volume.


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