According to the National Centre for Hydro-Meteorological Forecasting, the most torrential rain on September 19 was concentrated in Nghe An and neighbouring Ha Tinh, with the Vinh weather station recording nearly 400 mm.
The total was the highest daily rainfall recorded at the station in September in four decades, although it remained below Vinh's all-time daily record of 710 mm set on October 16, 2019.
The downpours caused flooding on several roads in Nghe An and heightened the risk of flash floods and landslides after days of wet weather.
At around 4.30 pm, a large section of a mountainside collapsed near Huoi Pai Village in Yen Na Commune, sending tonnes of earth, rocks, trees and other vegetation onto Road 543C and completely blocking traffic.
Yen Na Chairman Thai Luong Thien said several smaller landslides had occurred in the area in recent days, but Saturday's slide was the largest.
No casualties were reported. Authorities cordoned off the site and barred residents from approaching as large volumes of unstable earth and rocks remained on the slope, raising the risk of further landslides.
Provincial Road 543C is a key route serving villages in the area. Huoi Pai and Cha Lum villages, which are affected by the disruption, have a combined 309 households with about 1,200 residents.
Local authorities are arranging supplies and alternative access for residents while the road remains blocked. Clearing the debris could take four to five days if weather and safety conditions allow heavy machinery to enter the area, Thien said.
Households in areas considered at high risk have been moved to safer locations, while machinery will only be deployed once the slope is considered stable enough for clearance work.
Moderate to heavy rain and thunderstorms are expected to continue across Nghe An and Ha Tinh, with rainfall of 40-80 mm forecast and isolated areas in eastern parts of the two provinces potentially receiving more than 200 mm.
Quang Tri and Hue are also expected to receive 20-50 mm of rain, with isolated totals exceeding 100 mm.
Forecasters warned that further rainfall could worsen flooding in low-lying and urban areas and increase the risk of flash floods along small rivers and streams and landslides in mountainous areas.
