Flood disaster in Japan today

Abstract

Floods are the most frequently occurring disaster in Japan. When looking at the amount of flood damage in Japan from 1946 to the present as a five-year moving average, several peaks can be seen. The social and economic background of each peak can be read. Flood disasters also serve as a mirror to the contradictions and issues facing local communities and society.　 At its peak after 2020, flood damage is caused by extremely heavy rainfall in the form of linear rain belts, as well as levee breaks and overflows in important rivers directly managed by the national government. Since the period of high economic growth, Japan has experienced a decline in agriculture. This results in a decrease in the area of rice fields and abandonment of cultivation, which reduces the water retarding and water retention functions of the basin, leading to an increase in flood flow. Deterioration of arable land, especially in areas with unfavorable agricultural conditions, such as mountainous areas, is putting a strain on flooding downstream of rivers. In addition to the challenges of the decline of Japanese agriculture and a decline in food self-sufficiency, the number of flood disasters is rapidly increasing, and preserving farmland and knowing the land's water history are extremely effective measures to reduce flood damage.