Invited perspectives: safeguarding the usability and credibility of flood hazard and risk assessments

Flood hazard and risk assessments (FHRAs) and their underlying models form the basis of decisions regarding flood mitigation and climate adaptation measures and are thus imperative for safeguarding communities against the devastating consequences of flood events. In this perspective paper, we discuss how FHRAs should be validated to be fit for purpose in order to optimally support decision-making. We argue that current validation approaches focus on technical issues, with insufficient consideration of the context in which decisions are made. To address this issue, we propose a novel validation framework for FHRAs, structured in a three-level hierarchy: process based, outcome based, and impact based. Our framework adds crucial dimensions to current validation approaches, such as the need to understand the possible impacts on society when the assessment has large errors. It further emphasizes the essential role of stakeholder participation, objectivity, and verifiability in assessing flood hazard and risk. Using the example of flood emergency management, we discuss how the proposed framework can be implemented. Although we have developed the framework for flooding, our ideas are also applicable to assessing risk caused by other types of natural hazards.