Thirty seven people are known to have died and another ten are missing in a series of flooding and landslide related events in southern South Korea. The highest number of fatalities occurred in Osong in North Chungcheong Province, where a river burst its banks, causing an underpass to flood, and trapping 15 vehicles, including a bus on the evening of Saturday 15 July 2023. Nine bodies have now been recovered from the site of this incident, with nine people receiving hospital treatment, and five still unaccounted for.
At least seventeen people have died in landslide events in North Gyeongsang Province on Friday 14 and Saturday 15 July, with another nine missing. A rail engineer was injured when a landslide derailed a train, although fortunately no passengers were on the train at the time. Landslides are a common problem after severe weather events, as excess pore water pressure can overcome cohesion in soil and sediments, allowing them to flow like liquids. Approximately 90% of all landslides are caused by heavy rainfall.
Many of the country's hydroelectric dams are struggling after 75 cm of rain fell of much of the country on Saturday, with the Goesan Dam in North Chungcheong Province reporting an inflow of 2700 tonnes of water per second - equivalent to its maximum outflow. This has led to many dams releasing water at high rates, further raising the risk of flooding. More than 7800 people have been evacuated from homes in low-lying areas since Thursday. Thirty two stretches of road are reported to have been swept away by flooding or otherwise destroyed, as are 33 homes. Forty nine rivers are reported to have burst their banks. Two hundred and sixteen roads and the entire national rail network were closed for at least some time, although most of the roads and some of the rail lines have now re-opened. Twenty of the country's national parks have been forced to close.
The events are associated with the annual monsoon rains, which fall in Korea between mid-June and mid-August. Flooding and related incidents are not unusual during this season, but such large-scale problems have not happened in recent years. This years rains have been exceptionally heavy, with the country receiving an average of 30% more rain than would be expected, rising to 38.8% additional rain in the south of the country.
Monsoons are tropical sea breezes triggered by heating of the land during the warmer part of the year (summer). Both the land and sea are warmed by the Sun, but the land has a lower ability to absorb heat, radiating it back so that the air above landmasses becomes significantly warmer than that over the sea, causing the air above the land to rise and drawing in water from over the sea; since this has also been warmed it carries a high evaporated water content, and brings with it heavy rainfall. In the tropical dry season the situation is reversed, as the air over the land cools more rapidly with the seasons, leading to warmer air over the sea, and thus breezes moving from the shore to the sea (where air is rising more rapidly) and a drying of the climate.
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