Integrating Dynamic Adaptive Behaviour in Flood Risk Assessments

Abstract
Recent floods in the United States and Asia again highlighted their devastating effects, and without investments in adaptation, the future impact of floods will continue to increase. Key to making accurate flood-risk projections are
assessments of how disaster-risk reduction (DRR) measures reduce risk and how much risk remains after adaptation. Current flood-risk-assessment models are ill-equipped to address this, as they assume a static adaptation path, implying that vulnerability will remain constant. We present a multi-
disciplinairy approach that integrates different types of adaptive behaviour of governments (proactive and reactive) and residents (rational and boundedly rational) in a continental-scale risk-assessment framework for river flooding
in the European Union (EU). Our methodology demonstrates how flood risk and adaptation might develop, indicates how DRR policies can steer decisions towards optimal behaviour, and calculates the residual risk that has to be covered by risk-transfer mechanisms. We find that differences in adaptation decision-making outweigh the effects of climate change scenarios RCP8.5 and 2.6 on future flood risk. Moreover, we illustrate the relevance of adaptation by individual households, which appears more influential than the benefits from government protection in risk reduction in the short term. The results highlight the importance of integrating behavioural methods from social sciences with quantitative models from the natural sciences, as advocated by both fields.