Flood risk monitoring in Switzerland: Proof of concept

Abstract

The spatiotemporal evolution of flood risk is a challenge for flood risk management. Climate change, land-use change, human intervention, and socio-economic development lead to dynamics in the main risk components - hazard, exposure, and vulnerability. These dynamics require continuous adaptation of risk management strategies to ensure the safety level of humans and their assets in the long term. To enable adaptive flood risk management, it is necessary to monitor the risk evolution. Risk monitoring provides a better understanding of the risk evolution, identifies spatiotemporal differences, and detects location-specific drivers of change. However, flood risk monitoring concepts and their application are lacking. In this study, we evaluate the application of flood risk monitoring using a national case study (Switzerland) with data collected over a time period of 10 years. The continuously updated hazard maps, the number of houses in potentially endangered areas and the degree of damage are used to quantify the evolution of flood risk in terms of potential damage to buildings. The results show varying annual evolution of the flood risk in Switzerland and in different administrative units, the spatial variability of the flood risk evolution, and the variability in the evolution of the flood risk components. Between 2014 and 2023, the total flood risk in Switzerland increased by 26 %, the hazard area increased by 32 % and the exposure by 35 %. The disentangling of risk factors allows a better understanding of important drivers that increase or decrease risk. However, data availability and consistency are challenges for flood risk monitoring.