Surrey's Floodplain: CFAS
Surrey’s coastal floodplain is home to neighbourhoods, habitats, businesses and infrastructure
Surrey’s coastal floodplain is a large low-lying area that stretches across the City from Boundary Bay and Mud Bay along the Nicomekl and Serpentine Rivers towards Cloverdale and Newton. The area also includes the Little Campbell River area near White Rock and Semiahmoo First Nation.
Making up about 20% of Surrey’s entire land area, the floodplain is subject to both coastal and river flooding, with the coastal floodplain portions of the larger floodplain strongly influenced by ocean tides and weather.
Communities and People
- Many residential areas and neighbourhoods, including Crescent Beach, Panorama/Gray Creek, Cloverdale, Inter-River Area, Colebrook, Mud Bay, Nico-Wynd/Crescent Road
- Semiahmoo First Nation
- 1,500+ residents
- Approximately 20% of Surrey’s land area
Local and Regional Economy
- Over 30km2 of Agriculture Land in production
- 700+ jobs
- Over $100 million in annual farm gate revenue
- Over $1 billion in assessed property value
- Almost $25 billion annual truck and rail freight traffic
Parks and Environment
- Regional and City parks, beaches and recreation areas, including Surrey’s only public ocean beach
- Significant natural areas with very high biodiversity values, including foreshore, riparian and coastal areas
- Internationally important migratory bird habitat
- 13km of Provincial Highways
- Over 200,000 vehicle trips a day
- 31km of railway (freight and passenger)
- Regional sewer and water lines
- Major power transmission lines
- Natural gas pipelines
Flood management in Surrey
- Sea Dams
- Ditches, Flood Boxes and Pumps
A sea dyke is a long wall or embankment built to prevent flooding from the sea. A river dyke is an embankment built to prevent river flooding along the Nicomekl, Serpentine and Little Campbell Rivers. Most of Surrey’s floodplain, both coastal and inland sections, are protected by dykes. Many dykes in Surrey are also popular walking trails and bicycle routes.
Dyke in Crescent Beach
Sea dams are constructed along tidal rivers, like the Nicomekl and Serpentine Rivers, to keep saline water from moving upstream where it could have detrimental effects on agricultural irrigation. Sea dams are tidally influenced, shutting their gates when the tide comes in and opening again to let the river water exit the system once the tide moves out. The Nicomekl and Serpentine sea dams were first built in 1912 and 1913.
Sea dam in Serpentine Fen
Ditches, Flood Boxes and Pumps
Surface water flows into drainage ditches which then direct water through flood boxes located on river and sea dykes. During low tides and when the river water is low enough, the water drains into the rivers or the sea by gravity outflow gates. During high tide or flood events, electrically powered pumps help push the water out to sea or into the rivers.
A spillway is a lower portion of a river dike where, during flooding events, water can spill over into a holding area (called a cell). These cells are typically located on agricultural fields and protected by a smaller dyke system. Once the food event has ended and river level returns to normal, water held in the cells will drain back into the river through flood boxes or with the assistance of pumps.