GEOGRAPHIC INFORMATION SYSTEM-ASSISTED FLOOD HAZARD MAPPING OF BUCAO AND SANTO TOMAS RIVER WATERSHED

摘要

Flood is a natural hazard, and a natural process or phenomena occurring in the land that could be damaging for human as well as for natural environment. The flood hazard maps display flood hazard information in a given area which can be used in area development and management planning. The Geographic Information System (GIS) assisted hazard mapping is fast and reliable technique that can give information with just a click of your fingertips. The spatial analyst, integrated in GIS, was used in this study to develop a methodology for flood hazard mapping in Bucao River Watershed (BRW) and Santo Tomas River Watershed (STRW) in Zambales as a support tool in identifying flood susceptible areas in the watershed. Thematic maps such as elevation, slope, distance to major rivers and land cover were used to generate the flood hazard maps within the watershed. The flood hazard maps were created by weighting and ranking technique. Using the analytic hierarchal process or AHP, the factors were weighted according to their relative importance to each other and to their expected importance in causing floods. The generated flood hazard map was obtained by adding the weighted flood rankings of all the factors. Based on the generated flood hazard maps, 11.56 percent of the BRW total area and 17.20 percent of the STRW total area were susceptible to flooding.