In addition, the navigation capacity decreased due to the blockage of the river. The potential flood threat posed by river silting can be a more serious problem. Third, soil erosion has a serious impact on the economic development of some parts of Japan. According to a survey conducted by the irrigation sector, all areas with severe soil erosion are also areas where people live in poverty and are experiencing backward economic development. In these areas, poor soil fertility, shrinking arable land, and a single production structure have led farmers to the malicious phenomenon of "the poorer the cultivation, the poorer the cultivation". I will.