A 290-mm downpour in Nam Pam Hamlet, Muong La Commune, Son La Province, on July 5 triggered the area's first flood of the season, the Department of Dyke Management and Disaster Prevention under the Ministry of Agriculture and Environment said.
The flood also served as the first real-world test of Vietnam's first Sabo dam, which was constructed based on Japanese engineering standards.
According to on-site observations, the dam trapped large volumes of rocks, sediment, logs and other debris carried by floodwaters, significantly reducing the amount of material flowing downstream.
Local authorities and residents said the structure proved effective in mitigating the risks posed by flash floods. The ministry also noted that the dam successfully retained rocks, driftwood and sediment, helping reduce the force of floodwaters and protect downstream communities.
The dam is the first Sabo structure in Vietnam and was built under the "Enhancing Capacity for Flash Flood and Landslide Risk Reduction in Northern Mountainous Areas" project, financed through a Japanese non-refundable official development assistance (ODA) grant.
Construction began in September 2024 and was completed in April 2025. The open-type reinforced concrete dam is 61 meters long and nine meters high.
Japan has used Sabo dams since 1878 to control flash floods and debris flows. The structures are designed to trap rocks, sediment and fallen trees upstream, reducing water velocity, limiting riverbank erosion, lowering landslide risks and minimizing damage to downstream areas.
Encouraged by the pilot project's initial results in Nam Pam, the Ministry of Agriculture and Environment has proposed that the Japanese government continue supporting the construction of a comprehensive Sabo dam system across the Nam Pam stream basin.
The ministry said that the project would also provide a basis for evaluating the model's effectiveness and for mobilizing investment to replicate the technology in other flash-flood- and landslide-prone areas across Vietnam.
