Atmospheric river to bring heavy rain to B.C. South Coast Monday
Environment Canada is warning a heavy rain storm that it's calling an atmospheric river will fall on B.C.'s South Coast Monday.
A special weather statement notes the Lower Mainland up to Pemberton will receive 50 to 70 mm of rain while parts of Vancouver Island could see up to 150 mm over the course of the day.
The agency says the storm will bring heavy rain at higher elevations, including the North Shore mountains, and increase the risk of flooding and landslides.
The rain is expected to ease Tuesday morning.
An atmospheric river is an airborne stream of water vapour that condenses into precipitation and dumps large amounts of rain or snow in a short period of time.
This atmospheric river will be much weaker than the one that caused unprecedented flooding in the Fraser Valley in November 2021, says Environment Canada meteorologist Louis Kohanyi.
B.C.'s River Forecast Centre has also issued a high stream flow advisory for the same region, warning minor flooding in low-lying areas is expected as river levels rise quickly on Monday and peak on Tuesday and Wednesday.
King tide
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 wrote in a statement 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.
