Residential flooding is one of the costliest extreme weather disasters in Canada. While for new communities, flood mitigation measures can be embedded early on in the planning and development stages, older communities can be more vulnerable. These communities were developed with different criteria, policies, and regulations in place and often have a very limited capacity to cope with historical and current extreme weather events. This challenges municipalities as they try to prioritize their limited resources and use them effectively to minimize flood risks and maximize flood resiliency.

The National Standard of Canada, CSA W210:21, Prioritization of flood risk in existing communities, aims to help Canadian municipalities by providing practical and cost-effective approaches to strengthening flood resilience in existing urban and suburban communities.