The Study of Flood Peak Analysis at Khlong Tha Taphao and Khlong Chumphon Basins by Hydrologic Model

Abstract

                Khlong Tha Taphao and Khlong Chumphon Basins are subbasins of Peninsula East Coast Basin. The catchment areas of these subbasins are 2,227 and 521 square kilometers, respectively. Chumphon city which is located in the downstream portion of these subbasins has always faced up with several flood problems each year because of heavy rains from both moonsoon and tropical storm. Two severe floods which caused serious disaster were Gay Typhoon Storm at the beginning of November, 1989 and Zita Tropical Storm at the end of August, 1997.

                 Two hydrologic models namely NAM model developed by the Danish Hydraulic Institute (DHI), Denmark, and Hydrologic Flood model using Unit Hydrograph technique to calculate flood runoff from rainfall were used in this study. In calibration and verification of NAM model, the relevant data for the period 1998-2001 were evaluated. These two Hydrologic models were then applied for flood forecasting from Zita Tropical Storm occurred during 22-27 August, 1997 and Depression Storm occurred during 10-15 March, 2001. The performance of these two hydrologic models was investigated by comparing the obtained results with observed data at stations X.46, X.64, X.158 and X.53A.

                  It was found that both NAM and Hydrologic Flood models could be used for flood analysis in the studied subbasins with certain accuracy. Both models could be applied to estimate flood peak from storm rainfall to be used for making decision in flood management. However, NAM model is more reliable in determining flood estimation than using Hydrologic Flood model.