Public support for flood adaptation policy in Tokyo lowland areas

Sea level rise induced flooding is projected to cause significant damage to the low-lying coastal areas of many countries around the planet. Many households located in vulnerable areas have already started to adapt to flooding, although some empirical studies indicate that informal adaptation is reaching its limit and that more formal countermeasures by governments will be necessary to cope with the increased flood risks. In such cases, public support for flood adaptation policy is crucial to ensure a successful and timely adaptation, as these strategies can directly affect coastal residents. However, there is limited understanding on the mechanisms and factors that determine public support for flood adaptation policy. Thus, this study proposes a new model–the Foundation of Adaptation Policy Support (FAPS)–which integrates the Protection Motivation Theory and the Risk Information Seeking and Processing models. FAPS was tested using structural equation modelling with latent variables and data that was collected from a household questionnaire survey conducted in the Tokyo lowland areas (n = 388), with the super levee representing a policy that could be applied to sea level rise adaptation. The proposed FAPS model showed a good fit with the collected data, indicating that the strongest predictors of policy support include the perceived effectiveness of the policy and the importance of the issue of flooding to individuals. Other important predictors of policy support include knowledge about flooding, the opinions of surrounding people (i.e. family and friends), and the systematic processing by respondents of information related to floods. The FAPS model sets the foundation for understanding the mechanisms of public support for adaptation policy and provides new insights into designing and planning such policies in practice. Key policy insights Perceived policy effectiveness and the importance of addressing floods are the strongest predictors of public support for adaptation policy. Increasing people’s knowledge about flooding is essential to communicate the importance of adaptation policy. Investigating people’s knowledge and the perceived importance of the issue of flooding prior to designing policies can predict public preferences for certain countermeasures.