A METHOD IN EXPOSURE AND VULNERABILITY ASSESSMENT OF BUILDINGS EXTRACTED FROM LIDAR DERIVED DATASETS IN THE FLOOD PLAINS OF SANTO TOMAS RIVER BASIN AND BUCAO RIVER BASIN, ZAMBALES, PHILIPPINES

摘要

A total of 42,173 and 23,097 buildings were extracted in Santo Tomas River basin and Bucao River basin, respectively. Buildings vulnerable to flooding were identified based on the assessment of building exposure and flood hazard map generation in Santo Tomas River Basin and Bucao River basin, Zambales, Philippines. In the methods of generating flood hazard map, 3D building GIS database of the two river basins was generated through the integrated modern LiDAR technology and Geographic Information System software in which various datasets with 1m resolution LiDAR Digital Elevation Models (DEMs), geo tagged video captured data and high resolution imageries in Google Earth were utilized. Flood models were also developed to generate flood hazard maps with different levels using the combined HEC HMS and HEC RAS. The created building database and flood hazard maps used for the GIS overlay analysis produced a series of building exposure and vulnerability maps which correspond to 5-year, 25-year and 1 00-year return period rainfall events. Significantly, the results of this study were series of flood exposure maps and vulnerability maps with statistics at different rainfall scenarios observed that buildings exposed and vulnerable to flood are highest at 100 year return period. With the total of 42,173 building features extracted in Santo Tomas River basin, the accounted number exposed to hazard at 100 year return period were 24,738 buildings, 12,670 buildings and 4,620 buildings at low, medium and high hazards, respectively. A total of 8,938 buildings, 12,259 buildings and 4,556 buildings were identified that had high vulnerabilities to flood in terms of height at low, medium and high hazards, respectively. Moreover, 23,097 building features were extracted in Bucao River flood plains where 10, 118 buildings, 4,258 buildings and 7,433 buildings were the identified number of buildings exposed to flooding and a total of 2,427 buildings, 3,914 buildings and 7,204 buildings from the exposed were identified vulnerable in terms of height at low, medium and high hazards of 1 00 year return period, respectively. These maps can provide valuable informations to the local government units and the communities around Santo Tomas River basin and Bucao River basin in their flood disaster management and preparedness.