Hydrological investigation of a failure of the Huai Sai Kamin dam, Sakon Nakhon province, Northeastern Thailand

Abstract

The present study aimed to analyze hydrological data relating to the failure incident of the Huai Sai Kamin dam, occurring on 28 July 2017 following continuous heavy rainfall from the Sonca tropical depression. Structural and hydro-meteorological data related to the dam failure incident were assembled. From these data the incident rainfall return periods and excess rainfalls were estimated using flood flow simulation. Unit hydrographs and the channel routing procedures were conducted in order to derive inflow and outflow hydrographs. Rainfall analysis showed that a daily rainfall rate at 410 mm generated during the depression was equal to a 52-year return period. The reservoir routing indicated the amount of excess rainfall water in the reservoir and above the spillway to be 0.6 million cubic m, while the water contained in the reservoir was 3.0 million cubic m when an overtopping of the dam crest occurred. At the overtopping incident, the spillway outflow rate was 25.24 m³/s. This rate was three-time lower than the original maximum design rate of 85 m³/s. Although the outflow rate from the spillway was at its original maximum rate, the dam failure would still have occurred 6 or 7 h later. The original outflow rate at the spillway was slower, likely due to the spillway blockade by large amounts of water weed and debris. The diminished spillway capacity and the large amounts of water weed reflected inadequate dam design, construction and maintenance.