Assessment of a Flood Area by Using Satellite-based Rainfall (GSMAP) and IFAS in Nakhon Si Thammarat City, Thailand

Name: Sompop Sangpray

ID: – 

Title: Assessment of a Flood Area by Using Satellite-based Rainfall (GSMAP) and IFAS in Nakhon Si Thammarat City, Thailand

Type: Thesis

Abstract

          Nowadays, flood in Nakhon Si Thammarat become big problem. There are only three raingauge stations which does not enough and insufficiently for flood analysis. The utilization of satellite-based rainfall data can be the alternative data for flood extent estimation. In this study, the Integrated Flood Analysis System (IFAS) was establishing for flood assessment that uses satellite-based rainfall data as an apparatus to support the flood solution.

        The main objective of the study was to assess flood area in Nakhon Si Thammarat city and estimated the inundation area in rainy season. The other objectives were to compare the satellite-based rainfall data and ground-based rainfall data and calculate the river discharge in Klong Tha Dee basin. The comparison of total amount of rainfall in the study area show that the total amount of GSMaP rainfall and combined GSMaP rainfall ground rainfall were underestimated the observed rainfall 50% and 34% respectively. By using only GSMaP data, the accuracy of IFAS discharge was lowest compare to IFAS discharge using ground-based rainfall. IFAS discharge of combine GSMaP and ground-based observation denote the better result which was underestimated the discharge 27 percent. However the accuracy is not enough. Therefore, the ground-based rainfall is the most suitable data source for calculate the discharge. Nevertheless, in case of ground-based observation is not available, the GSMaP can be alternative data for flood analysis but the users have to carefully use and discreet. The HEC-RAS model was achievable applied to represent the Klong Tha Dee River basin corresponding to discharge. The discharge used to calibrate and validate the hydraulic model. The RMSE of discharge in validation was 6.33 for Ban Wangsai and 5.61 for Ban Napa. The R-Square of discharge of validation was 0.92 and 0.98 for Ban Wangsai and Ban Napa respectively.

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