B.C. flood risk compounded by mild temperatures, swollen rivers, saturated ground
Posted November 29, 2021 5:41 pm.
Last Updated November 29, 2021 7:55 pm.
B.C.’s south coast is bracing for a third wave of stormy weather, with another atmospheric river coming into the region on Tuesday.
“It will deliver a relatively strong punch, similar to what we saw this weekend,” said Armel Castellan, a warning preparedness meteorologist with Environment Canada.
“We are talking about 50 to 100 millimetres for the Lower Mainland, Sunshine Coast, Howe Sound, and the Fraser Valley. how found and the Fraser Valley,” he said, noting communities closer to the North Shore mountains will get the most rain.
“For Hope, we’re talking about 60 to 90 millimeters. For Abbotsford, we’re talking about 40 to 70. We also increase that amount into the coastal mountains near Coquihalla summit … 40 to 70 millimeters, as well.”
Rain a little heavier Tuesday than Wednesday. It's a bit out there still but could see some high elevation neighbourhood mixed precip early Saturday. @CityNewsVAN pic.twitter.com/ddSvF9AYxn
— Michael Kuss (@Kusswx) November 29, 2021
Mild temperatures could make the situation worse.
“The snow that … is on the brink of melting — because it’s really, really close to zero degrees — could certainly add to the total. So it’s not just a rain event. It’s not just a snow-melting event,” Castellan said.
The southwestern part of the province will be coping with a “successive storm event,” and the cumulative, compounding impact is the biggest cause for concern.
“Even if the third storm is not as bad as it could have been in the modeling leading up to today, it will be problematic because they are coming so close back to back with the runoff and the saturated soil,” Castellan explained on Monday.
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Since the onset of catastrophic flooding two weeks ago, there has been little let-up in challenging conditions. The potential for flooding from rain-swollen rivers persists.
“We’ve got flood watches remaining in effect for southern Vancouver Island, Howe Sound, Metro Vancouver, the Lower Mainland, and the Fraser Valley,” said David Campbell with the BC River Forecast Centre.
“We issued two new floodwaters this morning for areas including the Central Coast and northern Vancouver Island in recognition of … severe flooding potential over the next three days.”
The Nooksack River in Washington state, which meets the Sumas River, was receding Monday. Campbell says water dropped below flood levels, “but the active spilling … is expected to continue.”
A break in the wet weather is expected on Thursday and Friday with a weaker storm expected to arrive again on Saturday.
