Floodplain maps typically show the locations of watercourses or water bodies, surrounding features, ground elevation contours, flood levels and flood hazard area limits. They are typically used as a planning and regulatory tool.
Such maps are often 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 flood for most communities and is the estimated 1894 flood of written record for the lower Fraser River. Some floodplain maps also provide information on the areas where different flood construction levels apply.
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 continued developing flood maps until the early 2000s. Seventy communities were mapped under this program. The resulting maps are now outdated and do not cover all flood hazard areas across BC, but in many cases, they still provide the best information available. The 0.5% AEP regulatory flood standard for BC was used in the mapping.
Since the responsibility for flood regulation and associated flood mapping was shifted to local governments in 2004, some regional and local authorities have developed their own flood maps. But many communities are still lacking up-to-date flood maps. Organizations such as the BC Real Estate Association have been advocating for provincial government investment in a flood mapping program.