LAUSR

Water discharges at hydroelectric dams on the Imjin River, which flows through North and South Korea, generate abrupt water level increases downstream. We assessed infrasound signals from water discharges using an infrasound array located ∼32 km from the source and applied infrasound detection in a flash flood alert system. Using infrasound signals, there was a 79% detection rate for 48 water level increase events occurring in the river downstream during a 14‐year period (2008–2021). The detected signals had a low amplitude, long duration, and broad frequency range (0.5–15 Hz). The energy curves of the detected infrasound signals for selected events showed good correlations with the onset times and water level variations in water level records. These results demonstrate that infrasound monitoring can serve as a practical early warning system for impending flash floods resulting from unnoticed water discharges or sudden debris flows in mountainous regions.