Construction crews work to build a bridge for the Nooaitch First Nation near Merritt in November 2021. Snowpack levels in the Okanagan are some of the lowest in the entire province, while high levels in the North Thompson region makes for a “heightened concern for flooding” in Kamloops in the coming months. B.C.’s River Forecast Centre published its latest Snow Survey and Water Supply Bulletin Friday, which shows there’s a “slightly elevated risk for freshet-related flooding this spring” across the entire province. As of April 1, the average snowpack in the Okanagan is just 74 per cent of normal – one of the lowest in the province. Meanwhile, the North Thompson’s average snowpack is at 119 per cent of normal. “The combination of high snow pack in the Upper Fraser East, Quesnel and North Thompson indicates a heightened concern for flooding for Prince George, Kamloops, and the overall Fraser River,” the River Forecast Centre reports. While snowpack is by no means the only factor that can impact spring flooding, province-wide, the average snowpack is near-normal. “The combination of near normal April 1st snow pack, La Niña conditions forecast to persist through spring, mountain snow accumulation in the first week of April, and seasonal weather forecasts that predict cooler conditions for the province means a slightly elevated risk for freshet-related flooding this spring,” the River Forecast Centre says. “Every region is at risk for flooding, even if the snow pack is below normal. The weather conditions during spring play a critical role in the rate at which the snow melts. For example, a gradual warming under dry conditions is ideal to lessen the flood risk. A lengthy cold period with high amounts of precipitation followed by a sudden extreme heat wave could lead to catastrophic conditions, especially if additional rain follows.” Last year saw several extreme weather events that could impact flooding this year, including the June “heat-dome,” the summer’s widespread wildfires and the November “atmospheric river” floods. “Due to the significant erosion and possible changes in river channel morphology that occurred within many areas (including but not limited to the Coldwater River, Nicola River, Tulameen River, Coquihalla River and lower Fraser River), rivers may be at increased vulnerability to flooding at lower levels than previous freshet seasons,” the River Forecast Centre says. “Flows from snowmelt dominated watersheds impacted by fires tend to be greater and peak earlier as compared to undisturbed areas, even under normal weather conditions. Areas that recently experienced severe wildfire are at greater risk for higher peak flows.” Last year’s heat dome event saw alpine temperatures reach up tp 38 C, which triggered “extraordinary snow melt rates” where there was still snow. As the event didn’t hit the province until late June, there was less snow in the mountains to melt. “If such an extreme heat event occurred earlier in the freshet season when there is more snow to melt (May or early-June), it could lead to significant flooding at a provincial scale,” the River Forecast Centre says. The River Forecast Centre will release an updated seasonal flood risk forecast in the May bulletin, set to be released May 10.
