Assessing the Safety of the Nam River Dam considering Climate Change using Nonstationary Frequency Analysis of Extreme Rainfall Events

It has been reported that climatic change has intensified extreme events of rainfall, resulting in more severe floods. The safety of life and property in flood‐prone areas relies on the use of proper design floods for hydraulic structures such as dams and levees. In the current study, we revisited the design flood of the Nam River Dam to adopt the climatic variations of hydrometeorological variables and include recent datasets of extreme rainfall events. The nonstationary generalized extreme value distribution model with a time‐dependent location parameter was used in analyzing the annual maximum rainfall for the weather stations in the Nam River Dam basin. Furthermore, an additional estimate with a 10,000‐year return period was calculated to provide a probable maximum flood case for the Nam River Dam. The results illustrate that the new estimate is much higher than the original design flood estimated at the dam construction stage using a 200‐year return period. The new estimate with a 200‐year return period is 1.5 to 2 times larger than the original estimate of the design flood (10,400 m3/s), and the estimate is approximately 3 times larger using the 10,000‐year return period. It may be concluded that the dam, constructed based on the original estimate of the design flood, is severely vulnerable to climatic change, so the facility must be updated as quickly as possible.