AN APPLICATION OF HEC-RAS MODEL AND GEOGRAPHIC INFORMATION SYSTEM ON FLOOD MAPS ANALYSIS: CASE STUDY OF UPPER YOM RIVER

摘要

Most important disaster in Thailand is the flood, which frequently occurs and causes widespread losses in both properties and lives. Yom river basin is one of the basin in Thailand which is a narrow stream without regulated dam in upstream. Therefore, during rainy season, these area often suffer from flood. Phrae province where locate in a flood-prone area of upper Yom river basin have faced with flood almost every year. To manage the disaster situations, the approaches to assess the flood susceptible areas and the extent of disaster impact are the challenging tasks. This study aimed to develop flood hazard map, flood vulnerability map, and flood risk map along Yom river in Phrae province by using hydrological model of HEC-RAS and a set of procedures of HEC-GeoRAS for processing geospatial data in Geographic Information System (GIS). The model was calibrated using the rainfall observation data during flood seasons from 2007 to 2016. Then, the results of flood hazard map around the mainstream of the river indicated that 45.87%, 29.55%, 13.47%, 9.65% and 1.46% of the studied area are very low, low, moderate, high, and very high flood hazard class, respectively. The result of flood vulnerability map indicated that 11.35%, 2.37%, 27.97%, 25.69% and 32.62% of the studied area are very low, low, moderate, high, and very high flood vulnerability class, respectively. Then, the obtained flood risk map around the mainstream of the river indicated that 1.39%, 44.50%, 30.04%, 13.18% and 10.89% of the studied area are very low, low, moderate, high, and very high flood risk class, respectively over the studied area.