Last Updated 08 July 2022
Forecast water levels at Mission will be below 5.63 m for the next five days.
The Province of BC issues forecasts of water levels along the Lower Fraser River during periods of heightened flood threat. The forecasts, descriptions of the tools used in the development of the forecast, and the limitations and caveats associated with them can be found here. If you are curious about how forecasted flows and downstream ocean levels both play a role in the potential for flooding, we’ve just written a new blog post on the importance of tides in the water level forecast.
If you follow our blogposts – you’ll know that at Ebbwater we love maps, and we love QGIS. So, we thought we’d take the flood forecast, which is presented as a table, and quickly turn it into a map. Click on any of the markers (which denote gauge locations) to see water level projections for the next 5 days.
Please note that this is a simple exercise, and should be used for information only. The Province’s forecast data (see above) should be consulted for confirmation. Further, all the limitations to the model forecasts apply here too.
The floodplain extents on the map are estimated. The process we used to develop the floodplain can be found in this blogpost. We’ve also added the dikes to the map – the original dike layer was downloaded from GeoBC and attributed with dike assessment information that can be found in this report. Please note that the dike assessment was conducted in 2014, and should be treated with caution as some dikes have been upgraded since.
The map now includes maximum observed water levels in 2012 and 2018 (the most recent large flow years). These have been collected from reporting used to support the development of a new 2D hydraulic model of river.
Water Level Forecast Map
And here is the interactive web map, which shows forecast peak daily water levels. Click on any water level icon to explore how high the water is projected to be in the next few days.
The water level icons are coloured based on how the forecast compares to past flood events.
A comparison of the forecast with historic water levels
The Mission Gauge (on the north side of the River just west of the road bridge) has historically been used as a reference for flood levels on the Fraser. This is in part because it has been around for a long-time (as opposed to many other new gauges along the river), and partly because it’s in the geographic centre of the Lower Fraser River system. Please note the water level data is not available for 1990 and 1993-1996. The water level at this gauge is what triggers different response actions (e.g. dike patrols). Above 6.0 metres, and actions begin to ramp up, and above 7.0 m, continuous response activities should occur.
These triggers are based on historic information. A chart of past peak water levels on the Fraser River at the Mission Gauge is shown here. We’ve only seen it exceed 6.0 twice this century (in 2012 and 2018). And, the last time it exceeded 7.0 m was in 1972 (the third largest flood of written record, after 1894 and 1948).
The current projection for the next 5 days has water levels going up to 5.63 m at Mission.