Goesan Dam is about 15000ML in volume and is in the upper reaches of the Han River catchment that eventually flows through Seoul. It has a catchment area of 671 km2. The issue for the dam was that the calculated inflows exceeded the design outflow capacity of the gates by some margin (10.5%), hence the warnings of potential dam safety issues conveyed in the media and picked up internationally as the level exceeded 136.93 EL, the maximum planned flood level.
Elsewhere, a levee at the Miho River collapsed allowing rapid inundation of a 685-metre-long road tunnel with 14 fatalities. There was significant criticism of emergency managers with the likely failure identified 1 hour prior. A key focus of the police investigation was management and maintenance of the embankment that resulted in convictions related to its construction.