Assessment of flood risk and flood damage using Geospatial techniques: A case study of Sukhothai Province, Thailand.

Abstract

Floods are the most severe and frequent disaster in Thailand which cause enormous damages during the monsoon season almost every year. Sukhothai Province is one of the flood-prone areas that annually experience a considerable effect of the flood on both agriculture and residential areas. Therefore, the primary purpose of this study is to conduct a flood risk assessment in Sukhothai Province, Thailand, using Geographical Information Systems (GIS) which is a handy tool for disaster management and flood damage assessment. The study had applied the Frequency Ratio (FR) method to generate a flood hazard map with nine influencing factors of historical flood area, average annual rainfall, elevation, slope degree, land use, soil drainage, drainage density, road density, and the distance from drainage. Whereas, the Analytic Hierarchy Process (AHP) method was applied to create a flood vulnerability map with seven factors of historical flood area, average annual rainfall, elevation, slope degree, land use, soil drainage, drainage density, road density, and the distance from drainage. Then, the integration of hazard and vulnerability was done using GIS to assess flood risk over the study area. Lastly, flood depth-duration damage curve was created using data collected from questionnaires in the highest-risk areas of year 2011, 2017, and 2018.

The result showed that the flood prone area of high and very high floods hazards are 23.12% and 35.64% of the total area, respectively. These areas located in Si Samrong, Mueang Sukhothai, Kong Krailat, and Khiri Mat Districts. By validating the obtained flood hazard map with the Area Under Curve (AUC) method, it showed high accuracy with the success rate and the prediction rate of 95.05% and 94.77%, respectively. The obtained flood vulnerability map revealed high and very high vulnerability areas distributed over the study area. The area of flood vulnerability mainly found in two classes of the high-level and very high level of 25.98% and 16.40%, respectively. The results also showed that the very low, low, moderate, high, and very high risk area cover 26.15%, 11.07%, 21%, 13.59%, and 28.22% of the total area, respectively. Most of high and very high-risk area located along the main river and tributaries, including flat area. The obtained flood depth-duration damage curve can be a guide for government agency to estimate the cost of damage according to the depth of flood for the studied area.

In addition, the results of physical and social information at the Sub-District level and information on flood hazards, vulnerability, and damage can be used to manage as a valuable tool in applying risk management, flood mitigation, measures, planning, and management in Sukhothai Province.

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