In Hanoi, heavy rain is not just about catching a cold or a temporary disruption. Within just 30 minutes of intense rainfall, streets can be flooded up to half a wheel deep, paralysing traffic. Chronic flooding, driven by climate change, rapid urbanisation and an ageing drainage system, is listed as one of five major bottlenecks of Hanoi, according to the capital’s 100-year master plan.
After the 2025 rainy season marked by prolonged flooding, Hanoi authorities approved 10 emergency flood-control projects worth nearly VND 5.6 trillion (about US$216 million), expected to be completed in 2026. The projects include a major underground reservoir in the Old Quarter, as well as drainage upgrades in modern residential areas such as Resco, Ecohome and Ciputra.
The city’s effort to control flooding in 2026
According to the Hanoi Department of Construction, 10 flood-control projects have been classified as urgent and are scheduled for completion in the second and third quarters of 2026, ahead of the rainy season.
The 10 projects can be grouped into three categories:
- Improving drainage systems: Projects focus on upgrading drainage systems in residential and urban areas, including Resco, Ecohome, West Lake West, the Diplomatic Corps area, Ciputra, Vo Chi Cong Street, Long Bien, Dong Anh and Gia Lam, as well as expanding drainage capacity along Thang Long Boulevard.
- Upgrading canals and rivers to help water flow more efficiently, such as improvements to Thuy Phuong Canal, the To Lich River, and the downstream section of the Kim Nguu River connecting to the Yen So pumping station.
- Building new water storage facilities, including regulating lakes and underground reservoirs in areas such as Phu Do, Yen Nghia, Thuy Phuong and Me Tri, designed to temporarily store rainwater during heavy downpours.
At the same time, Hanoi is also moving ahead with plans to build two large underground flood-control reservoirs, which are scheduled for completion in 2026 as part of broader efforts to tackle urban flooding.
One of the two facilities will be located beneath Hang Da Market, in the heart of the Old Quarter. The underground reservoir will have a capacity of 2,500 cubic metres and a reinforced concrete structure, and will be equipped with regulating pump stations, each with a capacity of 0.09 cubic metres per second. The project is expected to ease flooding in the Phung Hung–Bat Dan–Duong Thanh–Nha Hoa area.
Hanoi has experience with underground reservoirs. In 2020, the city operated its first underground flood-control reservoir, located beneath a secondary school in the Van Mieu area. The facility is believed to have helped rainwater drain more quickly, easing flooding in the area, which had long been one of the city’s worst flood-prone hotspots during heavy rainfall.
Under the Capital’s master plan with a 100-year vision, Hanoi is studying to construct a massive underground rainwater storage system integrated with transport infrastructure to comprehensively address flooding. The mega underground reservoir, with a planned capacity of around 125 million cubic metres, is slated for construction in the period of 2036-2045.
Long-term solutions are needed more than urgent fixes
According to experts, despite multiple coordinated measures and substantial investment, the implementation of flood-control projects is still far behind the pace of Hanoi’s rapid urbanisation.
Scattered across different areas and employing varied approaches, the projects remain fragmented, largely experimental and reactive in nature, and have yet to tackle the city’s deep-rooted, chronic flooding problem.
Prof. Dr Nguyen Viet Anh, Head of the Water Supply and Drainage Department at the Hanoi University of Civil Engineering, pointed out that urban developments in Vietnam often replaced farmland with dense concrete surfaces before being connected to the city’s drainage network, significantly increasing pressure on an already overstretched system.
He argued that urban developers must be held more accountable, with clearer responsibilities and greater financial contributions to city-wide drainage infrastructure, rather than shifting the burden entirely onto public systems. “When building a new urban area, hydraulic modelling and trial simulations must be conducted to assess how much additional pressure is placed on the city’s drainage system, as part of the environmental impact assessment process,” he stressed on Suc Khoe Doi Song.
Le Trung Hieu, Deputy Director of the Hanoi Department of Finance, pointed out that Hanoi cannot address a 21st-century challenge with an outdated mindset that treats water as an enemy to be expelled. Instead, he said the city should adopt the “sponge city” model — a sustainable urban planning approach in which cities absorb, store, filter, and reuse rainwater rather than allowing it to run off and cause flooding.
For now, Hanoi’s flood-control efforts reflect a city searching for answers, balancing between urgent fixes and long-term ambitions. However, the city will need a comprehensive approach which integrates constructing works, land-use planning, green infrastructure, technology and smart governance to solve chronic flooding sustainably.
