Landslide That Took Lives... Why Precautions Are Needed Even After the Rain Stops

Increased Soil Moisture Raises Landslide Risk Even with Light Rain
Monsoon Rains Return Nationwide from the 22nd

As heavy rain continues in the Gyeongbuk region, causing landslides and resulting in casualties, recovery efforts are ongoing. However, concerns are rising that additional landslides may occur as strong rain is forecast again around the weekend. This is due to the ground being weakened after prolonged rainfall.

According to Gyeongbuk Province on the 18th, as of 12 PM, casualties from the heavy rain in the province are ▲21 dead ▲6 missing ▲17 injured.

In particular, the damage was concentrated in the Yecheon area where landslides occurred. A total of 11 people, including a couple in their 70s, were found dead, and the 6 missing persons, all residents of Yecheon, have not yet been found. It is estimated that 3 were buried by landslides and 3 were swept away by water, and search operations to find them are ongoing.

Additionally, landslides occurred in Bonghwa County and Yeongju City in Gyeongbuk, resulting in 4 deaths in each area.

The problem is that rain is expected to continue in the southern regions, keeping the possibility of landslides high. According to the Korea Meteorological Administration, heavy rain warnings have been in effect for five consecutive days in the Chungcheong area, southern regions, and Jeju Island, with more than 200mm of very heavy rain expected by the 19th.

On the morning of the 16th, Beolbang-ri village in Gamcheon-myeon, Yecheon-gun, Gyeongbuk, was devastated by a landslide and is awaiting restoration. [Image source=Yonhap News]

On the afternoon of the 18th, Kim Seung-bae, head of the Korea Natural Disaster Association, said in an interview with Yonhap News TV, "Typhoon Talim No. 4 is expected to make landfall near Vietnam, and this typhoon is likely to supply warm water vapor to our country," explaining that conditions are set for continuous rainfall on the Korean Peninsula.

Although the rain is expected to subside afterward, concerns about landslides remain difficult to dismiss. Since the soil moisture content has already increased after heavy rain, even a small amount of rain can trigger landslides. Therefore, experts advise monitoring the situation for another 2 to 3 days.

Lee Chang-woo, head of the Wildfire and Landslide Research Division at the National Institute of Forest Science, appeared on YTN Radio's "Wise Radio Life" on the same day and explained, "When a large amount of rain falls in a short time, rainwater fills the soil, making the soil heavier, and buoyancy occurs in the saturated soil between the soil and bedrock boundary, reducing frictional force," adding, "When heavy rain causes the soil to retain a lot of water, the possibility of landslides increases."

He added, "When the rain subsides, the soil continues to allow water to penetrate deeply and discharge it downward, so the underground water level inside the soil may temporarily decrease," but also noted, "Even if it temporarily decreases, rain clouds are coming back, and since the soil has already reached a certain level of water storage capacity, even a small amount of rain can cause landslides, making it a dangerous situation."

There is also a possibility of additional landslides in areas where landslides have already occurred. Professor Jang Seok-hwan of the Department of Construction Systems Engineering at Daejin University pointed out in an interview with YTN on the 16th, "If part of the ground has collapsed due to a landslide, the adjacent area already has a higher angle of repose (the stable angle)," adding, "In such cases, there is a higher risk of additional landslides, making it more dangerous."

Currently, recovery operations are being carried out by administrative authorities, firefighters, police, and the military in the landslide-affected areas. The 20th to 21st, when the rain is expected to ease, is the golden time for disaster recovery and rescue operations, but if additional landslides occur again, difficulties may arise.

Moreover, starting from the 22nd, the entire country is expected to come under the influence of the monsoon front again. A stationary front accompanied by low pressure is approaching, and another bout of monsoon rain is expected nationwide.