Khulan GUNTEVSUREN

Optimization of New Shelter Location Considering Flood Risk

Kazushi SANO

In this study, a program for Nagaoka City to calculate the optimal placement of new evacuation shelters in consideration of the positional relationship of existing evacuation shelters and the surrounding population in order to reduce the time required to evacuate people who have difficulty evacuating. The purpose is to optimize the location in consideration of the risk of flood damage. In this study, Nagaoka City is divided into two with the Shinano River as the boundary. Execute the program for each divided area and find the optimum layout. It is assumed that the population within each polygon in the Voronoi polygon evacuates to the shelter in charge of each polygon. When finding the optimal placement, calculate the population inside the inundation area and the population outside the inundation area, respectively. Here, the location of the new shelter needs to be outside the flood inundation area and disaster risk area, outside the forest area, not overlapping with the river, not overlapping with the road, and along the road. Also, when forming the Voronoi polygon, it is formed after excluding the existing evacuation shelters located in the flooded area. Next, calculate the population x shortest path in the polygon in charge of each new evacuation center inside and outside the flooded area, and find the optimum layout. The evacuation rate of evacuees inside and outside the flooded area is calculated based on the Ministry of Land, Infrastructure, Transport and Tourism's "Flood Damage Index Analysis Quote" in principle, with 80% of the population inside the flooded area and 40% of the population outside the flooded area evacuating. In this study, a 250m mesh is used, and the population in each mesh divided by Voronoi polygons is processed according to the ratio of the area of the mesh. As future issues, it is necessary to consider the following three points. The first is to consider the distance in the road network, not in the straight line distance. Second, if there is an inundated area during evacuation, it is necessary to consider not to pass through the inundated area. Third, it can be seen that the obtained results may not be certain because the evacuation rate differs depending on the time of day and regional characteristics. Therefore, it is necessary to consider the certainty of the evacuation rate in the future.