Long-term household flood adaptation under government policies: a coupled hydrological, hydrodynamic, and agent-based model

Flooding is one of the costliest natural hazards globally and is expected to increase in severity because of climate change and socio-economic developments. Therefore, it is important to implement adaptation measures that limit flood risk. Adaptation measures can be implemented by governments, but also households can flood-proof houses. This is viewed as a promising adaptation strategy, but it is unclear yet how many households will adopt these measures in response to government policies. Therefore, this study aims to understand to what extent various government policies, such as subsidies and information campaigns, can lead to increased implementation of household-level adaptation to reduce risk, such as wet-proofing or dry-proofing. To do so, we further develop a coupled hydrological, hydrodynamic, and agent-based model (GEB). We demonstrate this model for the Geul river in The Netherlands, where a severe flood event took place in July 2021.

The GEB model simulates river discharge over the last 30 years, including the July 2021 flood. When discharge exceeds bankfull conditions, we automatically simulate the flood using the hydrodynamic model SFINCS. Households in flood-prone areas make adaptation decisions on an annual basis, and additionally reconsider their choices following a flood event. This decision-making process is based on the Subjective Expected Utility Theory. Following this theory, flooding elevates the flood risk perception of households and this increased perception triggers adaptation decisions.

Our socio-hydrological simulations show that household adaptation is an effective way to reduce flood damages. Results can be used by policymakers to understand how much flood risk reduction can be achieved through household adaptation and to design strategies to increase adaptation uptake.