BIAS CORRECTION OF d4PDF RIVER DISCHARGE AND INUNDATION ANALYSIS IN THE CHAO PHRAYA RIVER BASIN

Abstract

 d4PDF runoff data was applied to river discharge simulation in the Chao Phraya River basin. The simulated discharge underestimated and overestimated observed one in the upstream Bhumibol and Sirikit dams and downstream Nakhon Sawan station, respectively. These different biases were corrected separately through 1) bias correction of wet and dry season volumes of dam inflow, 2) dam operation and river routing simulation with the bias-corrected dam inflow, 3) and bias correction of flood volume (over 2000 m³/s) at the Nakhon Sawan station. As the result, the return period of 2011 flood was evaluated in terms of flood volume as around 100 years. Inundation by the top 60 flood volume in d4PDF was simulated with a flood-inundation model accelerated with the ADU algorithm. Maximum flood volume varied among the events while flood area was similar to each other, implying that largest-class floods cause inundation in similar area to the 2011 flood with deeper flood depth.