FLOOD FREQUENCY MODEL FOR THE CENTER OF CHI RIVER BASIN IN THAILAND

The purpose of this research was to find the model for Flood Frequency Analysis for Center of the Chi river Basin. The water flow, which were obtained from the operation and maintenance center of Chi river Basin project, Royal Irrigation Department of Thailand, during 2009 to 2016 from four stations and to find model by Generalized extreme value distribution (GEV). The methods of estimation parameter were L-moments and LH-moments. The relative root mean square error (RRMSE) is evaluated as a criterion to find the best model and the return levels for various return periods were estimated. The results showed that all stations were homogeneity. Therefore all four stations were combined analysis. The Generalized extreme value distribution with L-moments was the best fitted and the return revel for 5 years to 50 years was between 457.37 to 3,771.97 cubic meters per second and the Wangyang station at Kalasin province had the highest return level.