In two days, 519mm 'Monster Rainfall in 200 years'

More than 500 millimeters of rain fell in a single day on July 17 in Seosan, South Chungcheong Province, marking a once-in-200-years deluge that drenched central South Korea. Several cities, including Hongseong, saw their highest daily and hourly precipitation levels on record. Torrential rain also struck the southern regions, with over 280 millimeters recorded in Changnyeong, South Gyeongsang Province, and Naju, South Jeolla Province. The extreme downpours led to multiple fatalities and widespread damage nationwide.

According to the Korea Meteorological Administration (KMA), Seosan received 519 millimeters of rainfall from midnight on the 16th through 3 p.m. on the 17th. This is the highest amount since weather observations began there in 1968. Considering Seosan’s annual average rainfall is 1,253.9 millimeters (based on 1991 to 2020 data), more than 41 percent of a typical year’s rain fell in just 15 hours. A new hourly rainfall record was also set, with 114.9 millimeters falling between 1:46 and 2:46 a.m. on the 17th.

A KMA official stated that the volume was statistically equivalent to an event that occurs once every 200 years based on daily rainfall and once every 100 years based on hourly intensity. Hongseong recorded 414 millimeters of rain on the same day.

Heavy rain also hit the southern regions that afternoon. Gwangju saw 210 millimeters of rainfall, while more than 200 millimeters fell in Damyang and Naju. Residents near Gwangju Stream were ordered to evacuate as water levels threatened to overflow. In Seoul, 140 millimeters of rain were recorded.

Due to the nationwide rainfall, the Central Disaster and Safety Countermeasures Headquarters issued its highest level of flood disaster alert. Flood warnings were issued for 23 locations. Buyeo and Cheongju were among 12 locations under flood alerts, while flood advisories were issued in 11 areas, including Jincheon and parts of North Chungcheong Province. In Seosan and Hongseong, three people were killed as homes and roads were inundated. In Cheongyang, two residents were rescued after being buried in a landslide.

More rain is expected through the morning of July 19, with additional damage likely. The KMA forecast up to 300 millimeters of rain for South Jeolla’s coastal areas, Busan, Ulsan, and South Gyeongsang, up to 180 millimeters for South Chungcheong, and up to 150 millimeters for North Jeolla and Jeju Island. The rainy season is expected to end around July 20, as the North Pacific high-pressure system moves entirely over the Korean Peninsula.

The storm claimed three lives, including two in Seosan and one in Osan. At 6:14 a.m. on the 17th, a 64-year-old man was rescued from a flooded car near the Seosan Tax Office intersection by Cheongji Stream but was later pronounced dead at the hospital. Another victim, an 84-year-old man who had gone missing near the downstream area of Cheongji Stream, was found dead around 11:24 a.m. Both were reportedly trapped in different vehicles as floodwaters surged.

In Osan, a 180-ton retaining wall measuring 40 meters in length and 10 meters in height collapsed due to heavy rain around 7:04 p.m. on July 16. It crashed into a car passing beneath the elevated road at the Gajang Intersection. The driver, a man in his 40s, was pulled from the wreckage at around 10 p.m. in cardiac arrest and later died at the hospital.

In Cheongyang County, two residents were rescued after a landslide buried their home in Daechi-myeon. In Tae Seong-ri village, Gongju, three residents who were clearing mud behind the community center were also temporarily buried but rescued.


Hye-Ryung Choi herstory@donga.com