General Views on Recent Rainfall and Landslide Events

The first chapter summarizes the background of landslide disasters, which includes the recent trends of heavy rains since 1945 in Japan and the size of induced disasters. Global climate change is an important cause of rainfall disasters but does not increase the annual rainfall. It makes the concentrated heavy precipitation more frequent and severe, thus increasing the risk. At the same time, human efforts to mitigate the disaster have been remarkable and have successfully reduced the size of the disasters. This successful situation may not last in future because the concentrated heavy rain is becoming more severe, and human efforts may not be able to catch up with it. At the same time, the public sectors are undergoing financial difficulties, and the people cannot afford the cost of the construction of safety facilities. This is the reason why less-expensive slope monitoring is considered important.