Cross-border evacuation and intermunicipal cooperation during large-scale flood disasters

The frequency of flood disasters has increased in recent years, leading to significant damage worldwide. Developing global risk-reduction strategies, such as cross-border evacuation, is necessary. The effective spatial range for intermunicipal cooperation is an important factor in implementing cross-border evacuation. Thus, this study investigates the effects of cross-border evacuation in large-scale floods by comparing inner and cross-border evacuation scenarios using GIS network analysis. The spatial range of inter-municipal cooperation is clarified based on a case study from Japan. The major findings are as follows: First, cross-border evacuation has the potential to reduce the evacuation time in many cities. Specifically, out-of-city shelters constitute the nearest shelter option for 24% of evacuees. Cross-border evacuation may reduce evacuation time by up to 14%. Second, cross-border evacuation is unsuitable for certain cities because of congestion at the boundaries. Third, community detection that finds the subnetwork with strong dependency between cities can suggest the effective spatial range for inter-municipal cooperation. Fourth, the shelters and route of cross-border evacuation considerably differ with inner evacua-tion. The evacuation plan requires specific guidance. This study helps identify the areas that would benefit the most from implementing cross-border evacuation and contributes to developing a wide-area evacuation plan in cooperation with neighboring cities.