Flood Risk and Mitigation Under Changing Land Use

In this study, we describe how flood hazard maps of the Kumozu fluvial plain were developed based on geomorphologic land classification maps and discuss the status of comprehensive disaster management with respect to flood mitigation in the lower reaches of the Kumozu River Basin in Mie Prefecture, Japan. Open levee-retarding basin systems are one of the traditional flood-mitigation strategies employed along the lower and middle reaches of river basins in Japan. Rapid changes in land cover and land use in the Kumozu River Basin have increased flood risk, and rapid urban expansion in the river basin has led to broad-scale encroachment of residential areas into agriculture land, reducing the area of flood buffer zones available for use as retarding basins. By assessing flood damage along the lower reaches of the Kumozu River Basin while taking into the consideration the role of traditional open levee-retarding basin systems, we clarify the utility of such systems in terms of flood mitigation and the importance of land use planning based on geomorphological land classification maps. Taken together, these results demonstrate the importance of incorporating nonstructural measures into river basin management.