Report Identifies Increased Debris Flow Risk
By Jo Anne Malpass
With the release of a BGC Engineering Inc. (BGC) Bush Creek East Fire Post-Wildfire Flood, Debris Flood, and Debris Flow Risk Assessment, the Columbia Shuswap Regional District and Shuswap Emergency Program held two public meetings in June to inform residents of the “very high likelihood” of these events in certain areas, which may put lives and infrastructure at risk.
BCG Geoscientists Carie-Ann Lau and Kris Holm explained to the large audience that because of the wildfire, the soil is similar to concrete so is unable to absorb water. Moving water can run off rapidly taking soil and debris with it, moving downward at the speed of a car. This can happen suddenly after a rainstorm, with no warning.
Some of these geohazards existed before, but increased risk is expected to continue for two to three years and then slowly decrease. April to November are the months of most concern. Increased temperatures in the summer months can lead to high intensity rainstorms that could set off a debris flow, after just two minutes, explained Lau.
Of 73 assessed watersheds in the burned areas, there are 10 zones with residences at high risk including areas from Little River towards Sorrento, Talana Bay to Celista, and the east side of Adams Lake.
The audience was advised to prepare to act before a storm. Know actions to take in a storm. Know where to go, not just on your property but also roads around you. Prepare an emergency kit for your home, vehicle and workplace. Plan a safe evacuation route and muster point. Know which rooms are safest if you have to shelter in place. Look/listen for an abrupt increase or decrease in water flow, unusually muddy water, shaking ground and a loud roar (sounds like a helicopter).
Mitigation around structures should be designed by a qualified professional. Sandbags are not useful and can even make it worse in a debris flood.
Derek Sutherland, GM of CSRD Community and Protective Services said they are working with BCG and negotiating with the province to institute an early warning system to forecast when an event may occur and communicate that to the community. Preparedness is funded locally through taxation, but the CSRD can’t fund prevention, except through the province. Large structural mitigation is not possible, because of the time frame and the need for grants that sometime take a year to get.
Questions about how this will affect building permits in the affected areas were deferred until CSRD Development Services staff has had time to analyze the reports and determine how rebuilding efforts may or may not be affected.
The CSRD has set up a separate webpage with links to the full report and a mapping dashboard that will allow residents to type in their address to see the geohazard risk level for their property. There is also a link to the presentation portion of the on-line meeting. https://www.csrd.bc.ca/553/Bush-Creek-East-Landslide-Risk.
View the entire Bush Creek East Fire Post Wildfire Assessment here.
Report Identifies Increased Debris Flow Risk
