Heavy Rainfall and King Tide Pose Flooding Risks for B.C.'s South Coast

Rich Pedroncelli / AP Photo

   Environment Canada is issuing a warning for a significant rainstorm, referred to as an atmospheric river, set to impact British Columbia's South Coast on Monday. According to a special weather statement, the Lower Mainland up to Pemberton can expect 50 to 70 mm of rain, while parts of Vancouver Island may see up to 150 mm throughout the day.

The forecast indicates that higher elevations, including the North Shore mountains, will experience heavy rain, raising concerns about an elevated risk of flooding and landslides. The atmospheric river is anticipated to subside by Tuesday morning.

An atmospheric river is a concentrated airborne flow of water vapor that transforms into precipitation, causing substantial rainfall or snowfall in a short timeframe. Meteorologist Louis Kohanyi from Environment Canada reassures that this atmospheric river will be less potent than the one responsible for unprecedented flooding in the Fraser Valley in November 2021.

Simultaneously, B.C.'s River Forecast Centre issues a high stream flow advisory for the same region, warning of minor flooding in low-lying areas as river levels are expected to rise rapidly on Monday, peaking on Tuesday and Wednesday.

Adding to the concerns, Environment Canada alerts about an exceptionally high tide, known as a king tide, that could lead to minor coastal flooding in Metro Vancouver, the southern Gulf Islands, and the Saanich Peninsula on Monday and Tuesday. Professor John Clague from Simon Fraser University emphasizes that these king tides, occurring twice a year when gravitational forces from the sun and moon reinforce each other, can cause substantial damage to shorelines.

Clague notes that the combination of strong inshore winds accompanying atmospheric rivers can intensify king tides, leading to severe flooding. In preparation for the king tide, the City of Vancouver has taken measures such as clearing shoreline debris, placing sandbags in coastal areas, and reinforcing sections of the seawall. City officials closely monitor changing weather patterns and are ready to close sections of the seawall if necessary to ensure public safety.