Some Interior communities face risk of flooding this spring, province says

Photo: BC River Forecast Centre

The B.C. River Forecast Centre says some low-lying communities in the Interior could be at risk of flooding this spring.

Jonathan Boyd, a hydrologist with the B.C. River Forecast Centre, said low to mid elevation communities within the Interior saw high snow values on March 1, possibly affecting the summer snow melt and increasing the risk of flooding.

“Lac Le Jeune recorded an all time record high snow value for March 1, which is pretty substantial,” Boyd said.

“And pretty consistent from Burns Lake, Vanderhoof, Williams Lake, Quesnel, the Chilcotins, Cache Creek and Nicola Okanagan, and Boundary, Grand Forks. It's areas in the Interior that aren't necessarily the big, high mountain ranges that are actually above normal snowpack.”

Boyd said that high snowpack levels contribute to high flow levels, which could prove detrimental if a heavy rainfall event coincides with the snow melt.

“Think of Cache Creek and the Bonaparte River — we've had several instances in the past five to six years. So hopefully they're quite aware of that. And whenever the snowpack is above normal, it just adds to that risk,” said Boyd.

Boyd said that the ideal would be to see the snow melt in April, when days aren’t long enough and temperatures aren’t hot enough to cause a rapid snow melt, decreasing the risk of flooding.

However, Boyd said forecasting the weather is a challenge when predicting potential flooding, as warm temperatures can cause the snow melt to occur earlier than anticipated.

“Also the potential that climate change could be impacting some of the storms that do arrive in the spring, that they may be a little bit more powerful and stronger and occur potentially more frequently than they used to," he said.

According to Boyd, Kamloops likely won’t see any flooding events from the Thompson River.

“Having been down at Riverside Park there and seeing some of the old flood levels, it would take a lot to get the levels up to that height,” the hydrologist said.

The North Thompson River saw its snowpack increase from 63 per cent of normal levels in February to 91 per cent in March. In the same timeframe, the snowpack feeding into the South Thompson River increased from 86 per cent to 105 per cent.

“The lower the snowpack the better, because the lower the snowpack the less risk for flooding,” said Boyd.

“But of course, it's a trade-off because if the snowpack’s really low, then it runs the risk for drought issues and especially increases the risk for wildfire. So ideally, kind of average is maybe the best case scenario, which could potentially limit the risks for floods and or drought.”

Boyd said there haven’t been any concerns of Kamloops flooding, especially when compared to recent years when snowpack levels were significantly above average.

“The North Thompson in 2020 for March 1 was 123 per cent of normal, and the South Thompson was 127 per cent of normal. And we didn't necessarily get any major flooding,” said Boyd.

Boyd said flooding occurs due to extreme weather conditions, such as the heat dome in 2021.

“The heat dome that happened in 2021 really frightened me in terms of what could conceivably happen,” he said, adding temperatures in 2021 reached 15 to 16 degrees above normal.

“If we were to get a situation like that in mid to late May, in a year where the snowpack was delayed in its melt and it was normal, I do think that that could conceivably push levels to flood stage,” Boyd said.

“So far, I'm not necessarily seeing anything drastic for the change from March 1 to April. If anything, maybe a potential extended dry period right now might offset some of the snowpack increases that we got in February.”

The River Forecast Centre will be releasing its next bulletin on April 1.