Province of British Columbia
In British Columbia, a provincial flood mapping program began in 1974, aimed at identifying flood hazard areas. Under the Canada/British Columbia Agreement Respecting Floodplain Mapping in 1987, the Province of BC continued developing flood maps until the early 2000s. At the time, 70 BC communities were mapped.
Maps were developed for the “design flood”—that is, the size of flood used for the design of flood infrastructure. In BC, the design flood is the estimated 0.5% AEP (“200-year flood”) for most communities and is the estimated 1894 flood of written record for the lower Fraser River (which is currently close to .2% AEP or “500-year flood”). Fraser River and Coastal floods are expected to become more frequent and
more severe in the coming decades under climate change. Standards for the design of dikes and other flood infrastructure need to be re-evaluated to account for projected changes in the flood hazard.
Provincial maps are now dated and do not cover all flood hazard areas across BC. Still, in many cases, they may still provide the best available information at a community level.
Responsibility for flood regulation and associated flood mapping shifted to BC local governments in 2004. In 2015, the federal government established the National Disaster Mitigation Program, a five-year, $200-million federal-provincial cost-shared program to support local governments and other organizations to develop and modernize flood maps (along with other types of flood risk assessment, planning and mitigation projects). As a result, some community flood maps have now been updated.
Why it Matters to Update Flood Maps
Communities change over time – and so does the nature of flood hazards. In the Lower Mainland, for example, coastal and Fraser River flood hazards are expected to increase in the coming decades and there continues to be new development in the floodplain.
Though a complex and expensive process, updated flood mapping is critical for flood management. Ideally, maps should be updated regularly as the landscape changes and as new information or flood modelling technologies become available.
The BC Real Estate Association and other organizations have advocated for provincial government investment in a flood mapping program.