Delayed snowmelt causes flooding concerns

·2 min read

The cool spring weather that continued into May has only increased concerns about the potential for flooding in BC watersheds, including the West Kootenay.

“The colder than normal April and early May conditions across British Columbia has increased the risk for flooding throughout the province by delaying the melt of snow,” says a May 15 report on the snowpack by the River Forecast Centre.

Provincial hydrologists say the delayed snowmelt has kept high-elevation snowpack at its highest levels recorded in a decade.

In an average year, approximately 18% of the annual BC snowpack has melted by May 15. This year, in comparison, “it is estimated that only 2.6% of the total snow has melted so far,” the provincial monitoring agency says.

“Both the West Kootenay (at 128%) and East Kootenay (at 124%) are above normal,” says the May 15 report. “Stations in the northern sections of the Kootenays are well above normal and may reach record values for June 1.”

Only a handful of automated weather stations in the West Kootenay reported in this survey period. At 144%, St. Leon’s Creek near Nakusp has the second highest snowpack level in the region (the record was near the Paulson summit, at 150%). East Creek in the Lardeau Valley area was at 130%, while Redfish Creek east of Nelson was recorded at 124%.

Snowpack is only one factor related to freshet flood risk, and much depends on shorter-term weather events. As temperatures rise in June, the magnitude and rate of snowmelt will increase. That lends to the danger of flooding as heavy summer rainstorms can push water levels higher.

“Weather conditions from May through July will determine the timing, magnitude, and rate of snowmelt, where heavy rainfall events can exacerbate snowmelt-driven flows,” the report says. “An extreme heat wave – like the heat dome in late June 2021 – could lead to significant provincial flooding if it occurred between late-May to mid-June.”

On the plus side – sort of – long-range weather forecasts say there’s a good chance the cooler and wetter La Nina that’s delayed the snowmelt will continue, perhaps as far as October and beyond.

The forecast centre is expected to release an updated freshet report on June 8.

John Boivin, Local Journalism Initiative Reporter, Valley Voice

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