Acknowledging residual risk behind dikes: Examples from the USA, Quebec (Canada) and France

Abstract

Although hydraulic infrastructure such as levees remain important for flood risk management in the USA, France, and Quebec (Canada), there is increasing emphasis on non-structural measures, such as regulatory flood maps, to reduce exposure and vulnerability, e.g., preventing people from building in high hazard areas. One key concept related to areas protected by levees is that of “residual risk”, i.e., the risk from floods greater than the design standard of the levees (levee overtopping), and from levee breach. In this article, we review the legislative framework for regulatory flood maps in the US, France, and Quebec (Canada), compare restrictions on land use within the designated high-hazard zones, and compare how residual risk behind protective structures is taken into account (or not) in regulatory flood maps. Comparing the Flood Insurance Rate Maps (FIRMs) in the USA with the “Plans de Prévention du Risque d’Inondations” (PPRi) in France and the “Cartes de Zones Inondables” in Quebec, we find big differences in how the USA, France and Canada manage residual risk behind the levees.