180 km/h Flood Hits Nepal on a Clear Day

Topographically, Nepal had an endless series of valleys from where the landslide originated, making energy dissipation difficult. In contrast, Switzerland loses energy in open areas and stops flowing, but Nepal could not. This lack of points for energy dissipation resulted in amplified flood damage.

With existing natural dams and lakes, the river continued to flow downstream, affecting surrounding areas, including India, where the damage spread.

Regions similar to Nepal, with high altitudes, low stability, and sparse vegetation, are vulnerable to flash floods. The entire Himalayan region, as well as the Alps, Andes, and Rocky Mountains, share these characteristics.

These areas always carry the potential risk of landslides and flash floods, and this risk can be further amplified by climate change.

In Korea, it rains before floods occur, and the Korea Meteorological Administration provides advance rain forecasts. Therefore, a certain degree of prediction is possible through the antecedent factor of rainfall. However, this Himalayan incident occurred on a clear day, without rain as a prerequisite, making prediction impossible.

In such regions, landslides frequently block rivers, forming natural lakes. The collapse of these natural dams on unpredictable clear days is a major cause of increased casualties.

Ultimately, the presence or absence of predictable rainfall is the critical difference between Korean-style flash floods and the Himalayan incident, requiring a different approach to disaster management in the Himalayan region.

Natural dams, as they are formed, typically have weak durability and are prone to collapse easily.

It is analyzed that the collapse of an enormous amount of rock and glaciers from the mountain peak, combined with these two events, led to the large-scale flood.

According to the Annals of the Joseon Dynasty, an earthquake occurred in Yangyang in 1681, affecting the Yangrak Mountain area of Gangwon Province. The records at the time state that huge rocks in the Seoraksan Valley collapsed all at once.

This suggests that large-scale rock falls due to earthquakes could also occur in the high-altitude regions of the Korean Peninsula.

An enormous amount of methane hydrate, known as 'burning ice,' is buried beneath the seabed of the East Sea. Recently, the seawater temperature in the East Sea has been rising rapidly, leading to an increase in the temperature of the seabed sediments.

If methane hydrate starts to melt and leak due to rising seawater temperatures, the stability of the East Sea seabed will significantly decrease. Weakening of the seabed foundation can trigger submarine landslides, which carries the potential for large-scale tsunamis.

Therefore, the rise in East Sea seawater temperature should be recognized as a serious issue directly linked to seabed geological stability, beyond being a simple environmental change.