Flood risk management at river basin scale: The need to adopt a proactive approach

This note examines the nature of floods, focusing in particular on the important function of flood volume retention and the conveyance of excess water out of river basins. Based on this account, it discusses flood management options that can be implemented as part of a proactive approach, one that seeks to avoid the disasters that may result from a “wait and see” approach. It describes the role of flood hazard and flood risk mapping in decision making and explores the distinct roles and comparative advantages of structural and nonstructural measures in managing flood risk. In addition, it provides guidance on flood risk assessment methodologies, including the role of numerical simulation models and their data requirements, and also includes a summary of the key principles of flood risk management. All these parts together serve to demonstrate the importance of understanding flood phenomena and assessing flood risks.

Key conclusions include that absolute flood protection in flood-prone areas is not possible or desirable, and some calculated acceptance of “living with floods” is necessary; flood risk management investments—particularly nonstructural measures—provide an attractive economic rate of return; and flood risk management interventions may have a significant impact (e.g., increase or decrease of flood risk) in areas outside where they are implemented.

This note focuses on flood risks (with a particular focus on river flood risks) with the objective of providing guidance to government officials, specialists, and other stakeholders across various disciplines involved in flood risk management.