The City of Coquitlam currently fronts four major rivers: Brunette, Coquitlam, Pitt and Fraser River.
Flood Events Analyses
Kerr Wood Leidal (KWL) analyzed the flood events, accounting for climate change, and generated Year 2200 Floodplain Maps (PDF) together with a table, which provides stationing (location) and flood elevations for the 2014, 2100 and 2200 flood events, including freeboard.
Developing in Floodplains
Fraser River Flood Level
The Fraser River Flood Level is established based on the historic 1894 flood levels, which saw flows of nearly 19,000 metres cubed per second in the District of Mission.
The Pitt River is connected to the Fraser River, and its flood elevations near the confluence of the two rivers are established from the Fraser River Flood Levels as follows:
2014: 4.92 metres Geodetic
2100: 5.84 metres Geodetic
2200: 7.15 metres Geodetic
Coquitlam River Flood Levels
The Coquitlam River Flood Levels were designed based on the design 200-year flood, which is a flood that can occur on average once every 200 years.
Coquitlam has several dikes surrounding low-lying properties that protect land from inundation if the river level rises. The properties protected by the dikes require pumps stations, which take the water from the lower lands and pump it into the river when levels are high.
As per the City’s bylaw, freeboard is the vertical distance added to the design Flood Level, to establish the Flood Construction Level (FCL). Provincially freeboard is the either 0.3m above the instantaneous 200-year peak water level or 0.6 metres above the daily 200-year peak water level.
Climate change can affect both peak sea levels and peak flows in watercourses. The current estimation for Sea Level Rise (SLR) is 1 metre by 2100 and 2 metres by 2200. The City’s floodplain maps (PDF) consider the projected SLR.