By midday on Sep 11, the HC1-02 underpass at the An Phu Interchange remained flooded after heavy rain the previous evening, forcing both directions to close and causing severe congestion at the city's eastern gateway.
Vehicles from the Ho Chi Minh City - Long Thanh - Dau Giay Expressway were diverted onto surface roads and through the An Phu roundabout, while authorities deployed personnel to regulate traffic.
The city's transport project management authority coordinated drainage efforts with the Department of Construction, contractors and emergency services. Firefighters and Ho Chi Minh City Urban Drainage Company sent pumps and specialized vehicles to the site, where a roughly 300-meter section of the tunnel was inundated.
Officials said heavy rainfall and runoff from surrounding areas overwhelmed the tunnel's pumping system. Water also entered the pumping station, further hampering drainage efforts.
It was the second flooding incident since the underpass opened in February 2026.
The 480-meter, four-lane tunnel cost more than VND342 billion and links the Ho Chi Minh City - Long Thanh - Dau Giay Expressway with Mai Chi Tho Boulevard. It forms part of the VND3.4 trillion An Phu Interchange project, now scheduled for completion in the second quarter of 2027.
River levels rise across the south
Flooding risks were also rising across southern Vietnam as water levels increased in the Mekong Delta and Dong Nai River.
The National Center for Hydro-Meteorological Forecasting said on Sep 11 that high upstream Mekong flows, combined with high tides, were pushing water levels higher.
At Tan Chau and Chau Doc, levels remained below Alert Level 1 on Sep 10 but were forecast to continue rising. Tan Chau could reach Alert Level 1, while Chau Doc may exceed it, with some downstream stations potentially rising above Alert Level 3.
Low-lying and riverside areas in An Giang, Dong Thap, Vinh Long and Can Tho face a heightened risk of flooding, along with possible erosion and damage to weakened dikes.
On the Dong Nai River, the water level at Ta Lai Station reached 112.57 meters at 7 a.m. on Sep 11, 0.07 meters above Alert Level 2.
Forecasters said levels would remain above Alert Level 2 over the next 6-24 hours, raising the risk of flooding and riverbank erosion in low-lying areas across the Dong Nai River basin.
Dozens of households affected in Dong Nai
In Phuoc Tan Ward, Dong Nai City, authorities and emergency personnel continued helping residents in Huong Phuoc neighborhood recover on Sep 11 after prolonged rainfall caused the Buong River to swell and flood residential areas.
Water surged into the neighborhood on the afternoon of Sep 10, inundating several roads to depths of around 0.5 meters in some locations.
Strong currents made travel difficult, while residents rushed to raise furniture and household belongings or move them to safer locations. Preliminary estimates showed that at least 50 households were affected.
Local authorities cordoned off flooded roads and restricted access, while militia members and neighborhood officials helped residents keep water out of their homes and move belongings to safety.
An underpass beneath the Bien Hoa - Vung Tau Expressway in Phuoc Tan Ward was also flooded, prompting construction crews to dig temporary drainage channels.
Residents said Huong Phuoc frequently experiences flooding during heavy rain when the Buong River rises.
Authorities have previously proposed dredging, widening, and upgrading about seven kilometers of the Buong River, together with improvements to Ba Buom Canal, to increase drainage capacity. The proposed project is estimated to cost about VND4.374 trillion.
