Disaster risk that remains, despite disaster risk reduction measures that may be in place, and for which emergency response and recovery capacities must be maintained.
Modified from UNDRR Sendai Framework Terminology on Disaster Risk Reduction (2023).
Residual flood risk in Jargeau, France
Levees designed for flood protection carry an inherent residual risk, i.e., risk of flooding greater than the design standard in case of levee breach (levee overtopping). Jargeau city, on the banks of the Loire River Valley, is protected by the Orléans Valley Levee system. The 51km long levee system promises protection greater than 250-year flood for 160 sq. km of valley bottom: 30km long and 5km wide, occupied by 70,000 inhabitants. During the 1856 flood, the levee protecting the east part of the city failed, flooding farmlands. This part of the levee was converted into a spillway and another levee was built to protect the south-east part of the city. The responsibility of recognizing residual risk associated with protection structures such as levees rests with local governments. The local government should also control development in areas of residual risk. For example, Frances has a top-down approach in this regard. It designates areas behind levees as part of the regulatory flood prone areas. There are mandatory land-use restrictions, building codes, and emergency measures with appropriate risk communication.
Source: Serra‐Llobet, A., Tourment, R., Montané, A., & Buffin‐Belanger, T. (2022). Managing residual flood risk behind levees: Comparing USA, France, and Quebec (Canada). Journal of Flood Risk Management, 15(2), e12785.