Investigation into the Nu Village Disaster

Recent research has identified a mud-rock flash flood as the cause behind the devastating event in Nu Village. Within a mere five minutes, an astonishing volume of 1.6 million cubic meters of mud, rocks, and water surged down from the mountains, leading to the village’s complete burial.

On October 2, the Geology Department at the University of Natural Sciences hosted a seminar titled “The Nu Village Disaster – Causes and Prevention Measures.” During the seminar, Associate Professor Dr. Nguyen Chau Lan from the University of Transport explained that following the incident in Nu Village (located in Bao Yen, Lao Cai province), Professor Tran Thanh Ha from the University of Mining and Geology and a team of specialists visited the area to gather important data.

“Initial findings show that the nu village disaster stemmed from a mud-rock flash flood. Approximately 1.6 million cubic meters of debris cascaded from the summit of Con Voi Mountain, situated 3.6 km from the village,” Dr. Lan explained.

This catastrophic flash flood, which occurred on September 10, completely engulfed Nu Village, affecting 37 households with a total of 158 residents. Tragically, 58 fatalities have been confirmed, with nine individuals still unaccounted for.

The mass of debris encountered a narrow bottleneck 100 meters wide, 2 km downstream from the point of collapse. This natural dam heightened the potential for a devastating flood release.

During the disaster, the region faced severe rainfall, amounting to a total of 633 mm, with hourly rain peaking at 57 mm, contributing to the rapid mud and rock flow.

Dr. Lan’s model calculations revealed that the mud accumulation depth varied between 8 and 15 meters, reaching up to 18 meters at its deepest. The flowing debris moved at speeds of 20 meters per second, covering the 3.6 km distance from the mountain to the village in just five minutes.

He highlighted that rainfall in Bao Khanh Commune reached 500 mm on September 9, indicating that landslides on Con Voi Mountain likely initiated on that date, though residents of Nu Village did not foresee the impending mud-rock flash flood.

“Due to Nu Village’s positioning on a geological fault line, it is especially susceptible to such hazards. Local authorities must discourage construction in these hazardous zones,” Dr. Lan strongly advised.

He further noted that mud-rock floods are not uncommon, citing a similar disaster in Seoul, South Korea, in 2011.

To mitigate future disasters, experts recommend that residents refrain from building close to streams or in landslide-prone regions. Currently, several northern provinces, such as Ha Giang and Lao Cai, are exhibiting signs of geological fractures, providing a window for preventive measures.

One practical solution is to cover the fractures with tarpaulin and create lateral drainage systems to stem groundwater seepage, thereby reducing landslide risks.

“This straightforward measure can be swiftly executed by localities before more advanced solutions are put in place,” Dr. Lan advised.

Associate Professor Dr. Do Minh Duc from the University of Natural Sciences highlighted the critical importance of early detection of landslide hazards, which could save lives even with just a brief warning period. Therefore, establishing early warning systems and timely responses is paramount.

Dr. Duc proposed the creation of a detailed database and mapping system to pinpoint high-risk zones, emphasizing various types of landslides and flash floods. Notably, rainfall acts as a primary trigger for these events, thus, key locations should be equipped with at least one rain gauge station to ensure timely alerts.