Southern B.C. set for a soaking as atmospheric river, king tide coincide
Flood, landslide risk due to heavy rain, wind; part of Hwy 1 closing for slope assessment; snow on high passes
UPDATE — Dec. 4, 2023: Flood watches issued for B.C.'s South Coast and Lower Fraser regions as atmospheric river arrives
Drenching rain, heavy snow, strong winds and high tides are converging on coastal and southern British Columbia on Monday.
Warnings have been issued for most of southwestern B.C., where a "potent and impactful" atmospheric river is forecast to make landfall with as much as 150 millimetres of rain falling on western Vancouver Island, Environment Canada says.
Inland Vancouver Island, the Howe Sound region and parts of Metro Vancouver, including the North Shore, Coquitlam and Maple Ridge, could get up to 100 millimetres of rain.
The Ministry of Transportation says it will close a 20-kilometre stretch of Highway 1 south of Lytton starting Monday night through Tuesday as the area is assessed for the danger of heavy rain on wildfire-damaged slopes along the route.
High winds are also in the forecast from northern Vancouver Island to Prince Rupert and Haida Gwaii, with gusts of up to 120 km/h expected to ease by this afternoon.
The province's River Forecast Centre has issued high streamflow advisories for the entire southwestern region of British Columbia, encompassing all of Vancouver Island, the Lower Mainland and the South Coast.
The atmospheric river is also expected to hit the southern Kootenay region in B.C.'s Interior, with the Elk Valley near Fernie and parts of Highway 3 expecting up to 100 millimetres of rain starting late Monday and lasting until Thursday.
Environment Canada is telling drivers on the Sea to Sky Highway from Squamish to Whistler and the Coquihalla Highway from Hope to Merritt that heavy rains will raise the risk of flooding and landslides along the routes.
It has also issued a winter storm warning for the Trans-Canada Highway from Sicamous to Golden, with up to 15 centimetres of snow expected along with ice pellets and the possibility of freezing rain.
King tide could bring flooding
Simultaneously, Environment Canada warns an exceedingly high tide could cause minor coastal flooding in Metro Vancouver, the Southern Gulf Islands and the Saanich Peninsula on Monday and Tuesday.
John Clague, professor emeritus at Simon Fraser University, says this tide, known as a king tide — an event that happens twice a year when the sun and moon's gravitational forces reinforce each other — can cause significant damage to shorelines.
"As sea level rises, the king tides are astronomical," said Clague.
He says heavy winds that accompany atmospheric rivers often make the king tides stronger.
"When they coincide, when you get the very highest levels in combination with strong inshore winds, you can get very severe flooding," he said.
The City of Vancouver said in a statement that staff have been preparing for the king tide by removing debris from shorelines, adding sandbags to coastal areas to protect infrastructure, and temporarily reinforcing parts of the seawall.
"Staff are closely monitoring changing weather patterns and will close sections of the seawall as necessary to help keep the public safe," says the statement.
With files from CBC News