4. Views on Recent Rainfall-Induced Slope Disasters and Floods

Risk of rainfall-induced disaster is universally discussed nowadays because of its possible relation with the global warming and Japan is not an exception. Many rainfall disasters occur in the recent years and it is very important to understand what is happening in nature now. This understanding will then help us foresee what will happen near future. With this viewpoint, the present paper reviews the recent rainfall disasters in Japan. Then the current risk possibly related with global warming/climate change is reviewed with reference to situation in some particular places such as lakes and rivers. Then the history of rainfall-induced disasters since 1945 is reviewed and the relationship between the damage size and intensity of rainfall is examined. This practice leads to a new vulnerability index and its temporal change is studied. This disaster review shows that the rainfall disaster had been decreasing until mid-2010s, after which it increases most likely due to increasing rainfall intensity while vulnerability index is held constant, or even increasing. Finally, the importance of people’s own efforts for safety is stressed and future scopes are presented.