Why do mountain passes continuously have landslides?

In recent days, prolonged heavy rains in Lam Dong have caused a series of serious landslides on many important mountain passes. According to experts, in addition to extreme weather factors, the causes of landslides include geology, planning, and maintenance work... which have caused the landslides to increase and become more complicated.

Drains buried by rocks and trees on Prenn Pass

The main "culprits" causing landslides

An expert from the Institute of Geological Sciences and Mineral Resources and construction engineers have pointed out the core factors leading to the frequent landslides and degradation of taluy slopes (the steep slopes of roadsides). The most basic physical cause is the characteristics of the mountainous terrain in the Lam Dong highland region.

According to geological experts, hilly soil is generally a mixture of rock and clay, with poor adhesion. This type of soil has hollow veins inside, making it prone to waterlogging after heavy rains, lasting at least 6 months each year in the Lam Vien plateau area. During prolonged rains, when the slopes are waterlogged, the large amount of water that cannot drain away will drag the soil and rocks down, leading to burying the drainage ditches, or worse, large landslides on the road surface.

However, experts also warn that landslides do not only occur during rainy days but can also occur long after, when the soil is still hydrated. The landslide cycle only ends when the entire geological foundation has dried out. Landslides in steep mountain passes are especially at risk in places where there are no old trees or where the forest cover is depleted. Experts say tree roots play an important role in holding the soil.

In addition, traffic pressure is also a significant cause. The mountain passes in Lam Dong are currently main roads, with a large number of vehicles, especially trucks and large containers carrying goods. This can easily cause subsidence, deterioration of the slope and increase the risk of landslides if not regularly maintained. Poor drainage and maintenance systems are also the reasons that construction engineers assess as making landslides increasingly serious.

It is easy to see that many mountain passes today have sewers, ditches, and cross-channels that have not been regularly dredged. The clogged sewers cause rainwater to not drain, overflowing onto the road surface, or some slopes do not have a drainage system to collect water flowing down from the top of the hill, causing water to overflow and leak onto the earthen slope, causing danger and this also accelerates the process of soil saturation, easily causing landslides. In addition, the construction materials of the slope are not guaranteed, which is also a factor causing landslides to occur.

Lessons from Japan

In the face of serious landslides, strengthening disaster prevention and control, especially in steep mountain passes during the rainy season, is extremely important. According to experts, the immediate focus should be on water management and slope reinforcement. Soil treatment, water collection embankments (both positive and negative slopes), and horizontal and vertical drainage systems should be given attention, especially during the rainy season to avoid further landslides. Most importantly, underground drainage measures should be applied to stabilize the slope.

In 2023, after a series of serious landslides, Japanese geological experts from Kawasaki Geological Joint Stock Company were invited by Lam Dong provincial authorities to survey and consult on preventive measures. After the survey, the experts shared their experiences and recommended that Lam Dong should establish landslide maps and warn of dangers in areas at high risk of landslides. The country is currently applying three main activities to minimize damage caused by flash floods and landslides: infrastructure reinforcement, early warning and evacuation of people.

After landslides that caused great loss of life in 2023, Lam Dong has zoned many areas at risk of landslides and installed landslide monitoring and warning systems, but the installation of monitoring systems has only focused on residential areas in urban areas and has not been implemented on mountain passes.

Expanding the early warning system to key traffic routes, combined with synchronous and serious technical solutions, will be the key to protecting people's safety and maintaining traffic connections, minimizing damage during the rainy and stormy season.

Source: https://baolamdong.vn/vi-sao-cac-cung-deo-lien-tuc-sat-lo-403910.html