A floodplain is flat or nearly flat land that is susceptible to flooding from a river, other watercourse, lake or other body of water. Floodplains are also called flood hazard areas because of the hazards they present to human settlement and development.
Unrestricted development within river and coastal flood hazard areas can increase the risk of loss of life, personal injury, property damage and disruption of critical infrastructure and services in the event of a flood. Development on one property can also affect neighbouring properties by changing the physical characteristics of the land and the flow and drainage of water.
Land use policy, regulations (such as zoning or flood bylaws, development permit areas) and other tools can be used to limit the type, size, intensity or location of new development and redevelopment in flood hazard areas.
Here are some common methods to manage land use and associated flood risk in flood hazard areas.
Zoning and land use designation: A municipality can zone, or designate through its official community plan or other regulation, floodplains and flood hazard areas and apply various requirements or guidelines for development and infrastructure in the area or zone. These designations should be informed by flood modelling and mapping.
Setbacks: Setbacks are the minimum distance of a building from a watercourse or water body or from the outer boundary of a flood hazard area. Setbacks can also account for the future erosion or migration of a stream corridor or shoreline. Restrictions on subdivision, new development, redevelopment or building expansion can be established for an entire flood hazard area or part of one. Options range from outright prohibition of building to conditions on size, location, site design and other characteristics. Setbacks can be regulated or administered as a guideline, and can apply both to new communities and existing developed areas (e.g., for expansions or redevelopment).
Permitted uses: Regulations can prohibit high-vulnerability uses (e.g., hospitals, emergency services or uses associated with hazardous substances) in flood hazard areas. They may allow low-vulnerability uses, such as parks and recreational uses. Communities can also actively plan to direct vulnerable uses, critical infrastructure and services, and higher densities to be located outside of flood hazard areas.
Property buy-outs and land use change: Property buy-outs involve a government acquiring properties to relocate residents and businesses outside flood hazard areas, most commonly implemented after a flood. This process tends to be costly and most likely to be undertaken at a small scale. Buy-outs are more common in the US, although there have been some initiatives in Canada in recent years.
In 1966, the Official Regional Plan for the Lower Mainland established floodplain boundaries and enacted a policy to prevent new urban development within these boundaries — except where urban development was already present. This approach led to continued and intensified development in existing flood-prone communities.
In the 1970s, some flood-prone areas in BC were classified as part of the Agricultural Land Reserve, a provincial zone where farming is recognized as the primary use and non-agricultural uses are restricted. This initiative has had a considerable effect in preventing urban development within agricultural flood hazard areas.
Up until 2003, the provincial government was responsible for approving subdivisions and local flood bylaws in flood hazard areas. In 2003, the Province delegated this responsibility to local governments. While there is no legal requirement to avoid or limit development in flood-prone areas, local governments have the option to:
- Develop flood hazard area bylaws and other development controls as long as they consider provincial policies and guidelines, including the Flood Hazard Area Land Use Management Guidelines.
- Grant flood hazard area land development exemptions, provided that the exemptions are consistent with provincial government guidelines or are certified by a suitably qualified professional.
- Establish requirements for subdivision in flood-prone areas, which includes engineering reports assessing flood hazards and restrictive covenants.
Municipalities in the Lower Mainland have exercised this authority to varying degrees. Development has continued in most flood hazard areas.