In northern Vietnam, under the combined influence of the residual circulation of Typhoon Matmo and orographic uplift, rainfall was intense and spatially concentrated. The core precipitation zones were mainly distributed in the Sông Cầu and Sông Thương basins and their tributaries, including the Sông Công and Sông Lục Nam. In mountainous and hilly regions, cumulative rainfall generally exceeded 300–500 mm, with localized extremes. The combined effects of prolonged heavy rainfall and short-duration intense storms caused rapid river rises, distinct flood peaks in multiple catchments, and widespread overbank inundation in several tributaries.
The research team led by Academician Wu Lixin, head of the Remote Sensing discipline at Central South University and a fellow of the International Eurasian Academy of Sciences, utilized the Disaster Reduction System for Belt and Road (DRS4BR) developed under his leadership. Using its Knowledge-Driven Flood Intelligent Monitoring (KDFIM) module and integrating imagery from China’s GF-3 satellite with publicly available Sentinel-1/2 data, the team conducted a rapid assessment and analysis of the flooding in northern Vietnam from 9 to 12 October 2025.
The upper Sông Thương basin was the most severely affected. Around Thai Nguyen and Sông Công, the steep terrain and rapid runoff convergence led to swift flood formation and significant flood depths. Remote sensing imagery showed persistent inundation in Thai Nguyen city and surrounding farmlands, with water depths exceeding 1 m in some areas. Floodwaters from upstream tributaries and the Sông Công merged into the Sông Thương mainstem within a short time, producing compounded flood peaks that propagated downstream. In the lower basin near Bac Ninh, the low-lying terrain and combined inflows from upstream and tributaries formed a pronounced flood-retention zone, resulting in extensive and prolonged inundation across urban and plain areas. The upper Sông Cầu basin was also heavily affected. Under the combined influence of complex terrain and heavy precipitation, floodwaters in the upstream Bac Giang section of the Sông Cầu converged rapidly, leading to widespread inundation and slow recession. As the floods moved downstream, they merged with flows from the Sông Lục Nam, further expanding the inundated area. At Chi Linh, floodwaters from these rivers converged with those from the Sông Thương, jointly entering the Sông Thái Bình and the Song Kinh Thai River before discharging into the sea, forming a multi-basin convergent flood pattern. The region’s flat terrain and poor drainage, compounded by tidal backwater effects, prolonged floodwater retention and intensified flood impacts.
Overall, this flood event in northern Vietnam was characterized by rapid upstream convergence, significant downstream retention, strong topographic control, and pronounced tributary interactions. The concentration of heavy rainfall, enhanced by terrain-driven runoff convergence, led to rapid flood propagation and widespread inundation across the basins, resulting in severe regional flooding.
Figure 1. Flood situation in northern Vietnam from October 9 to 12,2025
（Mapping Author: Jiao Zhijun, Liu Kun, Chen Biyan, Wang Wei, Wu Lixin）
