Conference Agenda

As climate change intensifies, frequent river flooding from intense short-duration rainfall will cause significant damage. Ecosystem-based disaster risk reduction employs green infrastructure, utilizing forests and retarding basins to prevent water concentration in rivers and reduce peak volumes. However, this approach requires a much larger spatial scale than gray infrastructure, which may disadvantage some residents. Therefore, understanding residents’ preferences in the watershed is crucial when planning flood control using green infrastructure. This study analyzed resident preferences for establishing retarding basins in the upper reaches of a river basin to mitigate flood damage downstream. A discrete choice experiment (DCE) assessed how the distance to mitigation areas affects perceived benefits. In March 2024, a web questionnaire targeting residents of municipalities in the upper reaches, which had previously experienced flooding, was administered, yielding 2,263 responses. Respondents provided opinions on constructing a retarding basin in the upstream area to mitigate downstream flood damage. This scenario assumed that construction was under consideration. Analysis of DCE data using a random parameter logit model revealed that benefits decrease as the distance to the damage reduction increases, even with the same degree of damage reduction. Furthermore, a latent class model identified two classes with different preferences. The results of this study will inform cost-effective plans for installing retarding basins and building consensus among residents regarding their implementation.