510 / 2019-02-28 17:26:23

Study on the geographical factors of building damages caused by the heavy rain event of July 2018. -Case study of Kure, Hiroshima prefecture-

Heavy Rain,Landslide Disaster,Flood Disaster,GIS

全体主题 > Urban Planning & Modeling

The heavy rain attacked to the west part of Japan in July, 2018 (The heavy rain event of July, 2018). The heavy rain was caused by the typhoon and a seasonal rain front in each place of the west part of Japan, and many damages were caused by landslide and the river flooding. The number of human damages were more than 650 and building damages were more than 50,000. Other, heavy rain disaster also occurs frequently in Japan after the 2000s. Because approximately 70% of the land is mountainous area and hilly area in Japan, and many farmlands are converted to residential area. Those are the factors of the large damages by the heavy rain disaster in Japan. Especially, the development in the dangerous zones caused by sprawl and the housing land development in the lower land make severe damages. Also, the following factors are seem to be crucial. First, the geographical factors of the natural environments such as the topography and vegetation and the catchment area. Second, the geographical factor of the city planning such as the city area expansion and the housing land development. Third, the amount of rain fall. Therefore, authors analyzed the relationship between geographical factors and the heavy rain disasters, and also considered damage reduction. Therefore, in this study, authors aimed at examining proper urban structure for the future, and also understanding a dangerous areas from the both viewpoints of the natural environmental factors and the city planning factors in the heavy rain event of July, 2018. In consideration of disaster mitigation, the future land use planning should also include the viewpoints of sustainable living environment with population decreasing and aging population. The target city was Kure in Hiroshima Prefecture in which the severe damages were caused by the heavy rain event of July, 2018. Because there are few flatlands, and residential areas spreads to the slope, it is reported that serious damage occurred.
In this study, authors made the damaged area in the target city on GIS using the aerial photo. Thereafter, authors analyzed the factors of the disaster from the viewpoint of natural environments by using decision tree method, and a relationship between the buildings located in the suffering range and the sprawl process of the city area from the viewpoint of city planning. Based on them, authors understood the danger zones of the heavy rain disaster and extracted the buildings which should be removed in the future from the viewpoint of the city planning by evaluating the disaster risk of each building in the area.
As a result, this study showed that the control of the disaster risk is possible by using the regulation for the development and the appropriate land use planning with understanding the geographical factors. And city areas should moves to safer living environment with shrinking is regarded as important.