The effects of last summer’s Cultus Creek wildfire could threaten a section of the CP Rail line southeast of Nelson, says a post-wildfire natural hazards risk analysis report commissioned by the province.
Last summer the Cultus Creek fire burned approximately 7,589 hectares on the west side of the main arm of Kootenay Lake.
Although there was sparse human settlement affected by the fire — it burned along the east-facing slopes above Kootenay Lake in the Next, Cultus and Midge Creek watersheds — areas between three watersheds were also burned.
The Ministry of Forests, Lands and Natural Resource Operations (FLNRO) report, written by Westrek Geotechnical Services, noted that the future effects of the fire are anticipated to be hydrological, including elevated streamflow, flooding and sediment-laden floods, as well as geomorphological, such as rockfalls, landslides and debris flows.
The post-wildfire effects are likely to last for at least three years or until vegetative ground cover on the burned slopes is re-established.
In one of the more severely burned areas, between Midge and Cultus Creek watersheds, the steep slopes could see sediment-laden runoffs that could reach the CP Rail line, especially if it is concentrated through the small creeks and gullies.
“Sediment, woody debris and water is expected to impact the tracks, ponding and infilling ditches, and potentially blocking drainage culverts,” wrote Tim Giles, senior geoscientist at Westrek. “It is recommended that CP Rail review the condition of their track and drainage structures and upgrade or repair, as necessary.”
Following a wildfire, the chances of soil erosion, landslides, and floods can increase. This risk can be enhanced with intense rainfall or rapid snowmelt, said Chris Johnson, RDCK manager of Community Sustainability.
“While this is not a heavily populated area, there are a number of recreational properties and an important supply line via the railroad that were impacted,” he said. “The information provided by the Ministry of Forests advises how conditions may have changed as a result of the wildfire, and we encourage residents or anyone planning to visit the area this year to update their emergency plans accordingly.”
Johnson said the Cultus Creek wildfire was first discovered on July 2, 2021 on the west shore of the south arm of Kootenay Lake within the Kootenay Lake Provincial Park.
The emergence of the fire resulted in the evacuation of residents and recreation sites in Electoral Area A in the Midge Creek to Next Creek areas between July 23 and 25.