INTRODUCTION OF FLOOD EVACUATION ROUTE SEARCH SYSTEM USING QGIS,POSTGIS,GRASS AND PGROUTING
The purpose of this system is searching safe route to a shelter, assuming flood occur.
This system is using simulation data about flood of river, road network data and location of shelters. The road network data are stored in PostGIS database, and prepared for pgRouting. Expected flood area data file is stored as GeoTiff by the elapsed time and place of the broken levee, and every pixel of these files have depth value of flood water. We made the QGIS plugin for this system to find capable route from a point on the map to shelter ,not using the submerged roads ,assuming flood. We used QuantumGIS 1.4 , and pgRouting to find route.
Using pgRouting, to search route to avoid flooded areas, we had to write in SQL conditions.But flooded areas were saved as raster files , we could not write a condition of PostGIS where submerged.So we did convert from GeoTiff files of flooded areas to polygons in PostGIS , using GRASS. We could make flooded areas polygon, using condition of water depth, from each GeoTiff files by elapsed time . At this conversion, we added the column of elapsed time from the collapse of levees burst to the table. Then we could query the non submerged route using pgRouting, with condition of elapsed time from assumed burst.And we could driving distance query with passing through flooded areas(e.g. where is a area we could go from a point within 20 minute,avoiding flooded route)
Without FOSS4G we would have been difficult to obtain tools for such spatial data usage.
I want to talk about effectively utilizing the spatial data FOSS4G have a great capacity.
This system made for The Ministry of Land, Infrastructure, Transport and Tourism Japan, Kanto Regional Development Bureau.
Yoichi Kayama - Aero Asahi corporation