Study of Flooding Volume in the Kolok Basin, Narathiwat Province

Abstract

          This paper presented the analysis of flood volume at X.119A station located at Lantu Bridge, Kolok Basin, Narathiwat province with the HEC-HMS model. Daily rainfall data from 6 stations 29042, 29052, 29092, 29102, 29112, and 29131, daily runoff data from station X.119A, and monthly evaporation from station 29131, were collected. Accuracy of rainfall data was checked using double mass curve method, and flood frequency analysis was conducted using Log-Pearson type III distribution method. The results of calibration (between 2007 and 2009) and verification (between 2014 and 2015) were used to determine coefficient of determination (R²) of the Kolok Basin. The resulted R²  for calibration and verification were 0.72 and 0.76, respectively. The results of the model parameters were as follows: initial abstraction of 60-130, CN of 51-65, % impervious of 0.20, lag time of 5,200-5,500 minutes, initial discharge of 3-6, recession constant of 0.90, ratio to peak of 0.45-0.65. The results from flood frequency analysis showed that the drainage capacity of the Kolok river was lower than 2 year return period, which indicated that the Kolok Basin has a risk of flooding every year.