A combination of healthy snowpack and expected cooler weather suggests British Columbia faces a “slightly increased” risk of flooding from spring runoff, according to the BC River Forecast Centre.
The April Snow report and water supply bulletinreleased Friday, found snowpack levels ranging from 74 to 134 percent of normal in various regions, with an average of 99 percent across the province.
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“The combination of near-normal snowpack on April 1, La Niña conditions expected to continue into spring, recent snow accumulation in the first week of April, and seasonal weather forecasts predicting cooler conditions for the province means a slightly increased risk for Freshets Floods,” the bulletin said.
“Snow cover is only one factor related to flood risk. Weather conditions from April to June determine the timing, extent and rate of snowmelt, and heavy rains can exacerbate the situation.”
The River Forecast Center noted that rivers affected by the devastating November 2021 floods could be at higher risk of flooding during the spring freshness, but thankfully snowpack in the Nicola, Similkameen and Lower Fraser regions was not above normal .
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The survey found that snow cover was well below average in the Nicola (69 percent), Chilcotin (72 percent), Okanagan (74 percent) and Vancouver Island (74 percent) regions.
The Northwest (134 percent), North Thompson (119 percent), Upper Fraser East (117 percent), and Upper Columbia (115 percent) regions showed above-average snow accumulation.
The Bulletin cites a 53 percent chance that a La Nina climate system, which has historically brought cooler and wetter weather, would persist through the summer, which could result in late-season snow accumulation or delayed snowmelt and increase flood risk.
“Seasonal weather forecasts from Environment and Climate Change Canada in late March indicate an increased likelihood of colder-than-normal temperatures from April through June for the province’s coastal and northern regions, as well as pockets in the southern interior,” the report said.
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The center forecasts near-normal spring flow rates for the Quesnel, South Thompson, and Skeena regions, and slightly above-average flow rates for Upper Fraser, North Thompson, and the Thompson River.
It said discharge in the Similkameen River and Cowichan River could be “well above normal,” with discharges as high as 120 percent of the average.
The River Forecast Center said that projections for Okanagan Lake, Nicola Lake and the Nicola River, and Kalmalka-Wood Lake are less certain based on an updated model for the region, but that snowpack levels in the region are “well below normal”. indicate a lower risk.
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https://globalnews.ca/news/8748585/bc-spring-flood-risk/ BC snowpack almost normal, but forecast warns of “slightly increased” risk of flooding