The River Forecast Centre has upgraded the North Shore Mountains, Howe Sound and Sea-to-Sky region to a flood watch, with heavy rain expected to cause rivers to rise rapidly this week.
The watch, issued Monday, Nov. 9, warns that river levels could approach or exceed their banks, potentially flooding nearby areas.
Another round of storm systems is expected to reach the B.C. coast Tuesday, following a series of atmospheric rivers last week. The heaviest rainfall is forecast for Tuesday and Wednesday, with rain continuing through the rest of the week.
Weather modelling indicates that Howe Sound, the Sea-to-Sky region and the North Shore Mountains could be among the hardest-hit areas on the South Coast. Warm temperatures through Wednesday could also melt shallow snowpacks at higher elevations, adding to river flows.
Hydrologic modelling suggests flows could reach levels seen, on average, once every five to 10 years, or higher in some areas. Uncertainty about where the heaviest rain will fall means those flows are possible throughout the watch area.
Smaller rivers and tributaries are particularly vulnerable to rapid rises and deteriorating conditions. Heavy rain and high streamflow can increase the risk of unstable riverbanks, erosion, submerged roads, flooding and landslides. People are urged to stay away from fast-flowing riverbanks and never drive across flooded roads, bridges or river crossings.
Residents are also advised to keep storm drains clear of leaves, which can block drainage and contribute to urban flooding. The flood watch also covers northern, western, central and eastern Vancouver Island, Kingcome and surrounding areas on the Central Coast, and the northern Fraser Valley.
The River Forecast Centre said it continues to monitor conditions and will provide updates as needed.
