Geographic information system for flood hazard area delineation and estimation of at-risk households at the community level: a case study of salaya sub-district, Nakhon Pathom Province

Abstract

Every year, Thailand faces flooding, the greatest natural disaster threat for the country. It is at the household level where risk outcomes first materialize. This study delineates flood-hazard areas in Salaya sub-district and provides estimates of at-risk households located in this area by using geographic information system (GIS) technology with Potential Surface Analysis (PSA) and Overlay Analysis. The analysis classifies areas into different levels of hazard, hazard zones and at-risk households. The results show that 41.6% of the sub-district is an area of “moderate” flood hazard, comprising 10.45 square kilometers. “High” flood-hazard areas account for 8.98 square kilometers (35.9%), “low” hazard areas represent 4.28 square kilometers (17%) and “very low” hazard areas account for 1.38 square kilometers (5.5%). As or the number of households in the hazard area, it was estimated that the highest percentage—1,160 households or 50%—are located in moderate flood-risk areas, followed by low flood-risk areas (560 households or 24%), high flood-risk areas (521 households or 23%), and very low flood-risk areas (70 households or 3%). All results are shown on a map of the study area with a 1:50,000 scale.