The depth of British Columbia’s snow pack fell slightly over the month of February, from 109 per cent of normal on Feb. 1 to 105 per cent of normal on March 1, 2022, according to the latest report from the BC River Forecast Centre.
In the Kootenays, the West Kootenay has 108 per cent of normal and the East Kootenay 111 per cent.
Measurements are taken from over 200 manual and automated snow weather stations around the province.
La Niña conditions, forecast to persist through spring, and seasonal weather forecasts that predict cooler conditions for the province means an elevated risk for freshet-related flooding, the report says. Snow pack is only one factor related to freshet flood risk. “Weather conditions from April through June determine the timing, magnitude and rate of snow melt, and heavy rainfall events can exacerbate the situation.”
By March 1, 80 per cent of the season’s snow pack has typically accumulated.
The report also has a weather forecast for the spring, and with La Niña conditions still persisting, the outlook is for an increased likelihood of colder than normal temperatures from March through May for the entire province. There is also the possibility that the East Kootenay and Upper Fraser East will have more than normal precipitation for those months.
Although the East and West Kootenay are not at an extremely high risk for flooding, the Upper Columbia in the Golden area has a snow pack of 123 per cent of normal, the highest since 1996. This, says the Forecast Centre, means there is a higher risk of flooding through the freshet, and the region may be at risk into late June due to significant high elevation snow pack.
The report also says that the unprecedented and catastrophic flooding that occurred last November due to the atmospheric river has caused significant erosion and possible changes in river channels, which may put those regions who suffered the worst flooding at more risk.
“The freshet season differentiates from the fall flooding season as flows tend to be sustained for longer periods of time during snowmelt compared to shorter duration rainfall events.”
Overall the worst case scenario for spring flooding, according to the report, is a period of persistent cool temperatures and wet weather into the late spring, followed by a sudden heat wave of longer than five days. High snow packs do not always mean flooding, without the weather contributing during the freshet.