Abstract
In our study, we analyzed changes in flood risk caused by transitions in land use in the Aikawa district of Kurume in Japan’s Fukuoka Prefecture, which suffered inundation damage in a heavy rainfall in July 2018, using old editions of maps, residential maps, city planning maps, a landform classification map for flood control, and a map of the predicted flood inundation area. The torrential rains caused inland waters in the Shimoyuge River and Egawa River watersheds, both branches of the Chikugo River, to rise. However, the Egawa River basin, in an urbanization control area, was almost completely undeveloped and suffered no residential flooding. By contrast, the urbanization of low-lying areas in the Shimoyuge River basin in the urbanization promotion area experienced increased damage from flooding. In particular, the Aikawa district in the Shimoyuge River basin became a logistics hub with the establishment of the transportation industry following the opening of the Kyushu Expressway and the Kurume Interchange. Moreover, with the opening of the Aikawa Bypass, roadside stores have opened along the bypass, and housing has been built around them, which has promoted overall development. Although urbanization has progressed, the area is located on a flood plain that is vulnerable to inundation, and the development of low-lying land through conversion to farmland has resulted in increased inundation damage. During the half-century between 1970 and 2020, the building area continued to increase, with a higher percentage of the area in the deeper depths of the flood inundation projection area. It is clear that the increased building area was constructed on land at high risk of flooding.
