Estimation of flood damages on namphong river by hec-ras

Abstract

Floods are regularly happening in the urbanizing Nam Phong watershed, the northeastern region of Thailand. The lower Phong Basin area regularly goes more or less under water every year in monsoon due to lack of flood protection and limited resources. The damage of flood normally courses property losses, houses and land use change to the lowland in the flood prone area. The objectives of the study were, 1) Determine the flood frequency and flood zoning of the Nam Pong River at a return period of 5, 10, 25, 50, and 100 years, 2) Mapping the flood damage from the simulation varied with the different return periods. In this paper, the estimation of flood damage based on various return periods on Nam Pong watershed (2993.95 km2) was carried out by 1D hydrodynamic simulation with HEC-RAS model which the runoff was simulated by the SWAT model for 10-year rainfall records (2000–2010), the Gumbel‘s method had been used to analyze the flood frequencies with various return periods and the water released from Ubolratana dam were also analyzed as scenarios for inputting to the HEC-RAS model. The simulation of inundated area was conducted using hydrodynamic program HEC-RAS.4.1 for the flood of 5, 10, 25, 50 and 100-year return periods. The simulation has revealed that the percent of flood damage is 20%, 23.2%, 27.8%, 34.3%, and 38.5% at return period 5, 10, 25, 50, and 100 years, respectively. The various flood damage mappings were prepared according to the simulation result using the software ArcView. The map showed that the flood damage with 50 and 100-year return periods had affected moderately to the agricultural and urban area. In the future, these two maps should be helpful in raising awareness of flood damages and in assigning priority for emergency preparedness in the affected area.