Hummingbird Creek Composite Hazard Rating

Sicamous Creek: (Download Report) This report provides a detailed hazard assessment of Sicamous Creek, which is located on the east side of Mara Lake, 2 km south of Sicamous, BC. The Sicamous Creek fan-delta2 is densely developed and crossed by Highway 97A. The fan-delta has formed by clearwater floods and debris floods over the past approximately 9,000 years. Between June 23 and 25, 2012, a major debris flood damaged buildings and roads on the fan-delta leading to millions of dollars in damages and an equally expensive lawsuit. Other notable debris flood events resulting in damage to roads, homes, and/or bridges occurred in the 1920s, 1935, 1955, and 1997. The objective of this assessment was to quantify debris-flood hazards to inform future hazard management on the Sicamous Creek fan-delta in the Columbia Shuswap Regional District (CSRD). Historically, debris floods occur, on average, every 10 to 30 years (approximately 5% annual likelihood). Debris floods will preferentially affect the northern portions of the fan-delta. Debris floods can damage the existing bank protection (riprap) due to bank erosion and threaten Highway 97A and properties along the banks of Sicamous Creek. Debris floods are less likely to result in life loss (compared to debris flows) but can lead to substantial economic losses. Hummingbird Creek (Download Report) The objective of this assessment was to quantify debris-flow- and debris-flood hazards to inform future hazard management at Swansea Point in the Columbia Shuswap Regional District (CSRD). Debris flows occur, on average, every 30 to 100 years (approximately 2% annual likelihood). Debris flows will preferentially affect the eastern portions of the fan upstream of the Highway 97A confluence and could result in life loss and building damage. Debris floods occur, on average, every 10 to 30 years (3% to 10% annual likelihood). Hummingbird Creek channel is likely to fill with sediment during debris floods and channel avulsions. Debris floods can also damage the existing bank protection (riprap) due to bank erosion and threaten Highway 97A and properties along the southern banks of Hummingbird Creek. Debris floods are unlikely to result in life loss but could lead to substantial economic losses. The effects of climate change are very likely to worsen the impacts of debris flows and debris floods on the fan-delta by creating more frequent and potentially larger debris floods and more frequent, and possibly larger debris flows in the future, primarily because more frequent and more intense rainfall is projected to occur in a warming climate. The frequency and size of debris flows and debris floods under a changing climate were considered in developing the frequency magnitude model for Hummingbird Creek (Table E-1; Figure E-1).