High Streamflow Advisory
October 15, 2021
The River Forecast Centre has issued a High Streamflow Advisory for the Fraser Valley.
A High Streamflow Advisory means that river levels are rising or expected to rise rapidly, but that no major flooding is expected. Minor flooding in low-lying areas is possible.
A moderate atmospheric river event is expected to impact the region starting Friday, bringing an extended period of rainfall across southwest British Columbia.
Environment and Climate Change Canada is forecasting 75-150 mm of total rainfall for most areas over the two-day period from Friday to Sunday. Higher rainfall amounts are possible, particularly over higher terrain, with the potential for localized amounts in the 150-250 mm range.
Temperatures are expected to rise, with freezing levels forecast to peak around 2500 m by later Friday. Recent snow accumulation at elevation has occurred over the past few weeks, with 5-40 mm of snow water equivalent currently being observed at automated snow weather stations throughout the region. Most of the snow on the ground is expected to melt during this event and will contribute additional runoff to rivers.
Rivers are expected to rise rapidly on Friday and into Saturday in response to rainfall, with peak flows expected on Saturday. Larger rivers will likely experience peak flows on Sunday. Current modelling is indicating the potential for flows in the 2-year to 5-year flows in most rivers through the region, and potentially higher depending on the rainfall rates and amounts that ultimately occur.
The public is advised to stay clear of the fast-flowing rivers and potentially unstable riverbanks during the high-streamflow period.
Get your home flood ready:
- Store valuables and important items or documents in water-tight containers or in high places, like on a tall shelf or upper floor.
- Clear gutters
- Keep nearby storm drains clear of debris
- Direct downspouts away from basements
The River Forecast Centre continues to monitor the conditions and will provide updates as conditions warrant.