Categorizing resident evacuation behaviors within a flood-protected area

Abstract

ABSTRACT Flood management due to global warming is one of the most important issues to be considered worldwide. Communicating about flood risk between government and residents is important for enhancing awareness of residents’ evacuation. However, not enough risk information is provided to residents for evacuation from floods (e.g. where, when, and how to evacuate). Therefore, an evacuation analysis linked with a time series of inundation depths was conducted in Kawajima Town, which is surrounded by a ring levee in the watershed of the Arakawa River, Japan. According to the analysis of evacuation by walking, the evacuation should be started by the time an evacuation instruction is issued to avoid getting caught in flooding before reaching shelters. Although the analysis of evacuation by car did not consider road and bridge closures, it indicated that approximately 40% of the town’s residents would likely have difficulty evacuating to even the nearest bridge or road. The central and southern part of the town was also identified as an area where a wide-area evacuation, i.e. outside the town, would be difficult if road and bridge closures were considered. The risk map identifies high-risk areas and districts in the central, southern, and southwestern parts of the town. It also indicates the need for structures for emergent use, such as small mounds or towers for evacuation starting at the breaching time (BT) in these areas. Since there is no area where all residents can evacuate at the start of breaching time, it is necessary to start evacuation to shelters immediately after the evacuation instruction is issued. Because the number of municipalities with similar problems will increase in the future in Japan, the study of evacuation plans from flood inundation for residents in Kawajima Town is expected to serve as a model case for other municipalities to consider.