Flood Susceptibility Analysis using Frequency Ratio A Case Study of Huai Nam Mong River Basin

Abstract

This research aims to apply geographic information system to analyze flood susceptibility in the Huai Nam Mong basin using the Frequency Ratio (FR) method and 7 flood causative factors (rainfall, elevation, slope, stream density, road density, surface drainage, Land use) to analyze together with the historical flood data from 2009-2023 to find the frequency ratio and weight of the factors. The inventory flood data were randomly separated into 70% training data and 30% testing data. FR methods were applied to assign the correlation values between class factors and the flood training data. Then the flood susceptibility maps were prepared and classified into 5 levels: the very high susceptibility area, the high susceptibility area, the moderately susceptibility, the low susceptibility, and the very low susceptibility. The results of the study found that 1) the very high susceptibility area was ​​240.79 sq. km. (8.98% of the total area), 2) The high susceptibility area 670.06 sq.km. (25.01% of the total area), 3) The moderately susceptibility area was ​​954.46 sq.km. (35.63 % of the total area), The low susceptibility area ​​423.28 sq.km. (15.80% of the total area), The very low susceptibility area was ​​390.08 sq.km. (14.56% of the total area), The mapping validation effort was examined by using area under curve for flood in the Huai Nam Mong River Basin. It showed that success rate curve was 84.31% and the prediction rate curve was ​​79.29%.