Scientists believe that a combination of synchronized solutions is necessary, including detailed mapping of high-risk areas, early warning systems, and the establishment of comprehensive data, to prevent a recurrence of landslides and debris flows in Làng Nủ.
This information was shared by a research team from the University of Transport, the University of Water Resources, and the University of Natural Sciences during the “Làng Nủ Disaster – Causes and Solutions” seminar held on October 2nd in Hanoi.
Associate Professor Dr. Nguyễn Lân Châu from the University of Transport stated that his research team has investigated and identified multiple causes leading to the disaster in Làng Nủ and other key areas in Lào Cai province. The primary cause is the phenomenon of debris flow – a type of flood that combines water, mud, and rocks, which can cause significant destruction to buildings and drastically alter the landscape. This phenomenon is characterized by rapid transformation and large volume, often occurring after prolonged heavy rainfall in steep terrain.
Làng Nủ village, Bảo Yên district, Lào Cai province after Typhoon Yagi. (Photo: Ngọc Thành).
The research team also pointed out that the accumulated rainfall in the three days before Typhoon Yagi was excessively high, causing landslides of soil and rocks that accumulated in a narrow section, creating a temporary dam that broke, leading to a massive flow of mud and rocks that surged down to Làng Nủ early on the morning of September 10th, flattening 33 houses and resulting in 52 fatalities. In addition to heavy rainfall, the highly weathered shale geological substrate, low intensity, and thick weathered layer also increased the risk of landslides during rain.
“Rainwater is the primary factor that causes landslides in areas with weak geological foundations,” Dr. Châu remarked. It is essential to base assessments of landslide risk on rainfall thresholds; if rainfall exceeds 40 mm and cumulative rainfall exceeds 250 mm, it can trigger debris flows.
He recommended that for areas where cracks have formed, it is necessary to cover them with tarpaulins or flexible plastic, using steel pins to prevent water from seeping into the cracks. Additionally, a drainage system should be constructed at the top and along the slopes to prevent water from directly seeping into areas with cracks.
Professor Đỗ Minh Đức, Head of the Geotechnical and Infrastructure Development Department at the University of Natural Sciences, National University of Hanoi, along with his research team, proposed the construction of a detailed database and the establishment of a mapping system to identify high-risk areas. They also suggested creating a database of natural and anthropogenic factors to assess risk levels. Based on this data, risk maps and scenarios can be developed to support management and control efforts, ensuring safety against natural disaster threats in steep regions.
The establishment of a early warning system combined with regular monitoring of geological changes is deemed “very necessary to minimize damage caused by debris flows.”
Medium- and long-term solutions include: prioritizing safety for populated areas; controlling the negative impacts of rainfall and surface water; protecting and developing forest resources; and creating comprehensive development plans for steep land areas, which were also recommended at the seminar.
Earlier, experts shared with reporters various solutions to mitigate damage caused by natural disasters. ThS Thái Bá Ngọc, an environmental geology expert from the National University of Ho Chi Minh City, noted that preventing geological disasters such as landslides and debris flows is challenging due to the vast and steep terrain of these areas, making it impossible to construct sufficient facilities for response.
Accordingly, in mountainous areas, it is necessary to zone and identify locations at high risk of debris flows and landslides. Localities must pinpoint high-risk areas within their provinces for monitoring and alerting residents. Research and analysis should be conducted to identify the spatial distribution of landforms, classify slopes, and understand geomorphic processes to clarify the primary causes of each type of disaster, thus providing a basis for zoning potential disaster-prone areas.
Mr. Ngọc proposed that in the future, a comprehensive monitoring system should be established to cover locations for early warning of debris flows and landslides, as well as a system of structures to prevent mud and rock flows and auxiliary structures. To implement these monitoring solutions, pre-feasibility studies are needed, including detailed surveys of geological structures, hydrogeology, and existing structures, to clarify whether active faults exist and to model and predict high-risk landslide areas. For structures in high-risk landslide zones, drainage ditches should be constructed along water flows from the mountains to roadways. Additionally, multiple terraces should be created along slopes to ensure appropriate design.
In the long term, Associate Professor Trần Lê Lựu, coordinator of the Master’s Program in Technology, Water Reuse, and Management (Vietnam-Germany University), believes that authorities need to effectively plan housing construction on mountainsides and in valleys. Buildings should not be constructed close to steep slopes to mitigate the risk of landslides and debris flows. Afforestation should be prioritized to cover bare hills and mountains. Rock cages and wire mesh should be installed on mountainsides to prevent soil erosion and landslides. Before each rainy season, relevant authorities should conduct surveys to assess the potential for debris flows in their areas and prepare evacuation drills when necessary.
