South Korea city hit by almost a metre of rain and deadly landslide

Torrential rain has triggered a deadly landslide in Geoje, South Korea, after the southern city received close to an entire summer's rainfall in a matter of days. At least one person died when mud and rock struck an apartment building in Okpo-dong at around 4:42 a.m. on Monday, burying its first floor. Police and firefighters rescued three residents from the building, but one was found in cardiac arrest and was later pronounced dead at hospital. Two people were injured in Geoje and two others in nearby cities, according to the interior and safety ministry.

The rainfall was exceptional. Geoje received 805.7 mm of rain from Saturday through to 8 a.m. Monday, with cumulative totals reaching 912 mm by 6 p.m. that evening as the rain continued. Nearby Tongyeong recorded 671.9 mm during the same period, while other parts of South Gyeongsang province received between 240 mm and 340 mm. At the height of the storm, rain was falling at up to 100 mm per hour across the Geoje area.

The downpour caused widespread disruption. Roads flooded repeatedly across downtown areas as drains backed up, around 20 roads were closed to traffic, and city buses, intercity buses and taxis stopped running. Power was cut to about 1,500 homes and businesses, and twelve schools and kindergartens were reported flooded. Geoje city authorities issued an emergency alert in the early hours of Monday warning of a high risk of overflow at Mundong Reservoir and urging nearby residents to move to higher ground, and banned traffic around Gohyeon Stream as water levels rose sharply. Around 70 residents had evacuated to safe areas by 8 a.m.

The event illustrates how extreme rainfall can rapidly turn a local slope problem into an urban emergency. When rainfall intensity reaches this scale, slopes can become saturated, pore water pressure rises, and soil or weathered rock can lose shear strength. If drainage is overwhelmed, runoff can also erode channels, mobilise debris and push mud into buildings, roads and low-lying areas.

For cities built close to steep slopes, rainfall-triggered landslides pose a challenge that extends beyond emergency response. Mitigation typically involves slope hazard mapping, drainage maintenance, debris-flow barriers where appropriate, rainfall thresholds for evacuation, and regular inspection of slopes above residential areas. Events of this intensity also raise a broader question for practitioners: whether drainage and slope protection sized against historic rainfall records remain adequate where storms can deliver a substantial share of a season's precipitation in a matter of days.