Role of household climate change adaptation in reducing coastal flood risk: The case of Shanghai

Climate change intensifies the frequency and severity of floods - the most devastating and costly climate-induced hazard. Government adaptations such as dikes or beach nourishments are important, yet insufficient in the face of worsening hazards. They reduce the hazard probability, but the local actions at the household level determine the extent of damages and inequalities in its distributional impacts on various societal groups. To design effective policies and risk reduction strategies it is critical to quantify the speed and scope of the household adaptation uptake and the resulting damage prevention. This is especially the case for distributional impacts (i.e., how different societal household groups adapt), which are often neglected. Quantifying both aggregate and distributional impacts of household climate change adaptation (CCA) on flood risk fosters the design of tailored flood risk management policies which allocate resources to the societal groups that need them most. This thesis presents a state-of-the-art agent-based flood model in downtown Shanghai, China to understand the role of household CCA in reducing coastal flood risk both in its aggregate and distributional impacts. To model the households’ exposure to climate-induced floods we overlayed the geolocations of 18.039 residential buildings with 21 inundation maps that depict dike failures and dike overtopping under different climate-change scenarios. We further parameterized households using context-specific micro-level survey data from Shanghai and depicted households’ adaptation decisions using an extended version of the Protection Motivation Theory. Our results show that autonomous household adaptation (adaptation without government policy) to climate change plays an essential role in reducing flood damage in downtown Shanghai. However, despite the considerable adaptation uptake, the residual damages increase over time due to the effects of sea level rise and land subsidence. This shows that autonomous household adaptation alone is insufficient to keep pace with the increasing severity of climate-related flooding, as it is constrained by barriers in the form of adaptation measure costs and regulations. Thus, additional policies are needed to overcome these barriers. These policies should take into account differences in adaptation behaviour and damage prevention among societal household groups. Specifically, our results indicate that households with lower worry, self-efficacy, and income adapt measurably slower to climate-induced floods, which makes these household groups significantly more vulnerable to flooding.Link to the flood-ABM code: https://github.com/jlechn01/Shanghai-Flood-ABM The updated thesis PDF document includes a minor change in the acknowledgements (European Research Council project SCALAR).Complex Systems Engineering and Management (CoSEM