Areas where high intensity burns occurred in the Wiseman Creek watershed over the summer are where a debris flow is likely to begin. (BGC Engineering photo)

Areas where high intensity burns occurred in the Wiseman Creek watershed over the summer are where a debris flow is likely to begin. (BGC Engineering photo)

Sicamous trailer park at increased risk of debris flow following summer’s wildfire

Columbia Shuswap Regional District looking at mitigation options

Removal of a trailer park is one option suggested in response to the increased likelihood of debris flows near Sicamous following this summer’s Two Mile Road wildfire.

On Monday evening, Dec. 13, the Columbia Shuswap Regional District (CSRD) hosted a public meeting at Sicamous’ Red Barn Arts Centre to discuss post-wildfire landslide risks in the Two Mile area.

Leading the meeting was Matthius Jakob and Hazel Wong of BGC Engineering. The company has been working in the area of Wiseman Creek for the past nine years and conducted a post-wildfire assessment in October. Jakob’s presentation focused on debris flows occurring along Sicamous and Wiseman creeks and making their way towards Two Mile, subsequent to the destruction of the landscape that occurred in the 2,500 hectare Two Mile Road wildfire.

A key point shared in the presentation involved the Sicamous Creek Mobile Home Park, at the mouth of Wiseman Creek in Two Mile, being at increased risk of debris flows.

Jakob explained a debris flow is not the same as a debris flood, which is what he said occurred in Two Mile in 2012. He said Swansea Point experienced a debris flow in 1997.

“If you want to imagine the difference between a debris flood and a debris flow, you take a Home Depot bucket, fill it with say 20 per cent dirt and rest water and you swish it around and then run it down a kid’s slide, that’s a debris flood,” said Jackob. “Now if you mix half dirt and half water and you swish it around and slide it down a kid’s slide, that’s a debris flow… it behaves completely different from a debris flood.”

Read more: Province eyes post-wildfire debris flow mitigation plans along Highway 97A near Sicamous

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Jakob explained the destruction caused by this summer’s wildfire in the Wiseman Creek watershed has made it so that lesser rainstorms that wouldn’t have done so before the fire could now trigger debris flow events.

A slideshow presented by Jakob included a number of maps showing potential debris flow events that may occur in the Two Mile area over the next two to three years as vegetation regrows. Beyond 2023, debris flow hazard is expected to substantially diminish.

The slides showed it is likely debris flows will occur over the next two years. However, it is likely they will be small, and may or may not reach the trailer park. However, Jakob said he is unwilling to gamble on not being prepared should a larger, more destructive debris flow occur. He said of larger debris flows, which could travel at speeds up to 23 to 25 km/hr, once you hear it coming, it’s too late. Such debris flows pose a risk to life and property.

Options for mitigation suggested by Jakob included the strategic upland placement of engineered piles that would serve to block logs, as well as a large deflection berm and basin, also placed upland. A rainfall warning system was also suggested that could be used to issue evacuation alerts. Another option, said Jakob, is moving the trailers out of harm’s way.

The task now, Jakob explained, is to determine what options are feasible to do technically and financially, as quickly as possible.

“Once Hazel and Matthius get back to us with their thoughts on the best strategies going forward, it’s our job to go to Emergency Management BC to try and secure funding to implement some of those plans,” said Derek Sutherland, CSRD team leader for protective services. “In the meantime… we have some short-term strategies we need to explore including the early warning system that BGC is developing. We need to get that in place fairly quickly so… before we get those mitigations in place, we know what the trigger points are to force an evacuation of the area to keep people safe.”

Sutherland said the CSRD would be engaging with residents of Two Mile, particularly the Sicamous Creek Mobile Home Park, to help determine the best possible system for the community.


lachlan@saobserver.net
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bc wildfiresColumbia Shuswap Regional DistrictSicamous

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