North & South Alouette River Flood Risk Information
In November, 2021, an ‘atmospheric river’ swept through southern BC delivering unprecedented rainfall levels. The rain volumes resulted in landslides and flooding that closed major roads and bridges for the region. In Maple Ridge we were fortunate that the storm abated before damage was done to the roads and bridges along the north and South Alouette rivers which would have blocked access into the Silver Valley neighbourhoods.
While these two rivers have independent rainfall catchment areas, their downstream floodplains can interconnect during rainfall events. As a reminder, both rivers are unconfined (without dykes) and flow rates are driven by local rainfall intensities. In some circumstances, BC Hydro can provide some flood attenuation for the South Alouette River, however this ability is dependent on rainfall intensity, available storage volume and the dam spillway capacity.
The City has exerted a lot of effort studying these two watercourses over the years culminating in the North Alouette and South Floodplain Analysis in 2016 and the completion of Integrated Stormwater Management Plans in 2021. Here is information specific to the flood risks associated with this part of our City.
This map outlines areas of flood risk associated with the North & South Alouette Rivers.
As noted, the City has done a lot of data collection and planning work for these watercourses.
Since then, the City has commissioned additional work to better correlate precipitation within the two rainfall catchments with BC Hydro dam operations to more accurately forecast flood events during storms. This work will culminate in a Flood Response Plan for the Alouette Valley.
Weather and River Forecasts, Live Gauges and Utility Information
Information on weather, gauges, hydro, natural gas and statistics on past floods can be found at these links:
Voyent Alert! Is a multi-purpose communication service provided by the City of Maple Ridge to keep you informed of critical events like fires or floods as well as day-to-day communications such as road maintenance and closures, water advisories, etc. Go to https://www.mapleridge.ca/453/Public-Safety and follow the links to get you and your family signed up for alerts.