Safety First? Lessons from the Hapcheon Dam Flood in 2020

Floods change the living environment and threaten public health, while dam construction has often been made to protect and mitigate floods. Meanwhile, an exceptionally high outflow, five times higher than the maximum historical outflow, was discharged on 8 August 2020 from the Hapcheon Dam (HCD), which is located at the middle of the Hwang River, South Korea. As a result, the 2020 flood event occurred in the downstream area, flooding the villages located downstream of the HCD, and damaging agricultural and residential areas. The current study investigates the cause of the flood and how the outflow affected the downstream area. The investigation showed that the Hwang River and the streams connected to the Hwang River experienced piping and overflow in several levees downstream. The frequency analysis of the rainfall upstream and the inflow to the HCD illustrated that the rainfall return periods are only 5–30 years for different durations. The return period of inflow to the HCD was only approximately five years. Sustaining a high-water level before the flooding season for future environmental use caused an exceptionally high outflow. Lowering the water level might have prevented damage to the downstream area. The 2020 flood event provided an imperative lesson to water managers and policymakers, demonstrating that the HCD and downstream safety must be prioritized over water conservation for environmental use.