Following heavy rains in central Vietnam due to the impacts of storms and tropical depressions over the past month, the region has seen multiple landslides with fatal consequences. Most notably, Quang Tri, Quang Nam and Thua Thien-Hue provinces have recorded several landslides that made national headlines, killing at least 62 and leaving dozens missing.

Trinh Xuan Hoa, deputy head of the Vietnam Institute of Geosciences and Mineral Resources under the Ministry of Natural Resources and the Environment, said deforestation and construction, among other factors, were to blame for triggering landslides in central Vietnam.

"Human activities including deforestation and road construction, etc. have hastened geological changes in the area. Leveling mountains and destroying taluses for construction destabilize the terrain, create steeper slopes and sacrifice local vegetation. This fuels the risk of erosion and landslides," he said, adding erosion occurred mainly on mountain slopes, in residential areas or along roads and other man-made structures.

"However, rain is the first factor to trigger landslides. Research shows just 100 mm of rainfall or even less could saturate the soil," he said, adding rainfall of up to 2,000 mm over several days last month had caused flooding and eventually landslides in central Vietnam.

Central Vietnam's steep elevation toward the sea, dotted by sparse plantations, along with complex geological features like thick weathering layers, heighten the risk of erosion and landslides. Man-made forests mostly comprising the Acacia genus and routinely replanted after several fellings, make for weakened soil cohesion and underdeveloped root systems, thus impeding efficient water retention, Hoa noted.

Erosion-prone areas

Hoa cited a landslide in Quang Nam's Nam Tra My District, which struck Tra Van Commune along terrain about 600-900 m above sea level, and with a natural slope of 20-30 percent. The erosion-prone area is 65-70 percent covered by man-made forests, with short and steep creek and stream systems heightening the risk of natural catastrophe.

Quang Tri, Quang Nam and Thua Thien-Hue are all classified provinces at high risk of landslides or with landslides concentrated in one area, according to an environment ministry survey on erosion and landslide warning capabilities across mountainous areas in Vietnam, said Hoa. Quang Tri, surveyed in 2018, has 241 erosion points, 147 of which are located in Huong Hoa District, accounting for 61 percent of all erosion sites in the region.

Thua Thien-Hue, surveyed in 2019, has 205 erosion and 151 potential erosion points, situated mostly along main traffic routes and residential areas like Ho Chi Minh Road and national highways 74, 71 and 49. A Luoi District in particular has 122 erosion points.

Quang Nam, also surveyed in 2019, has 1,286 erosion points and 723 potential sites. Several of its districts, including Bac Tra My, Nam Tra My, Tien Phuoc and Phuoc Son, are at high risk of erosion, data revealed.

Ha Tinh and Quang Binh provinces too may be at great risk of erosion, the survey found.

Natural disaster monitoring tools are ideal for boosting erosion warning capabilities since they could provide very accurate predictions, according to Hoa, who lamented their current insufficient supply in the country.

"For now, we can learn from Thailand by equipping villages with a rain gauge. Once rain levels reach a certain point, people could be evacuated. Such a method is cheap and easy to implement," Hoa said.

Local authorities should also create safe zones for evacuation purposes during natural disasters, while prioritizing forest protection, especially in upstream regions and erosion-prone areas, he stressed.

Floods and landslides in central Vietnam have killed at least 159 and left 71 missing last month, Prime Minister Nguyen Xuan Phuc told a meeting last Friday. Casualties included military officers and officials.