Lack of synchronization leads to inefficiency
Statistics from functional sectors show that during the heavy rains in 2025, Hanoi recorded dozens of flooding points, concentrated in the main basins: inner city, To Lich River, Nhue River and Long Bien - Gia Lam area. In some places, the water receded after a few hours, but there were also flooding points lasting one to two days, disrupting daily life and production.
Living for more than 20 years in the Phung Hung - Duong Thanh area, Ms. Nguyen Thi Lan (Hoan Kiem ward) shared: "Our people are no stranger to the scene that every time it rains heavily, we have to put up our belongings and park our motorbikes. There are days when it rains in the afternoon but the next morning the water still hasn't receded completely. Flooding becomes familiar, but familiar does not mean accepting it.
In fact, Hanoi's drainage system is "carrying" a city that is developing much faster than its infrastructure capacity. Many areas that were previously fields and ponds - places where rainwater can see and drain naturally - have now been concreted. Meanwhile, the drainage network of sewers and rivers has not been upgraded synchronously.
In an exchange with Lao Dong newspaper from October 2025, after a very heavy flood in Hanoi, Prof. Dr. Dao Xuan Hoc - Chairman of the Vietnam Irrigation Association - said that since 2009, functional agencies have had drainage plans for Hanoi. If it can be done according to the plan, Hanoi will only be flooded for about 2 to 3 hours when it rains heavily, not last for several days as it is now.
This expert explained that flood control for a city consists of two parts: First, overall drainage - that is, the system of canals and rivers leading to the water receiving area must always be lower for natural water flow; this part is under the management of the irrigation sector. Second, the system of culverts and ditches in the inner city, under the responsibility of the urban water supply and drainage unit. Both parts need to be synchronized.
According to the design, Hanoi's drainage system is calculated to be able to handle rainfall from 70mm to 100mm/hour - meaning that when it rains, the water will recede at that time. However, in reality, many areas are still deeply flooded every day.
Prof. Dr. Dao Xuan Hoc said: "Hanoi needs to focus on building macro projects, that is, river systems, pumping stations, and drainage canals to the Red River and Day River in accordance with the approved plan. When water has a place to drain out, projects to renovate inner city sewers will be effective.
Efforts of Hanoi
In the report on the main contents of the Capital's Master Plan with a 100-year vision announced by Hanoi at the end of January 2026, in the section "Breakthrough tasks, solving existing bottlenecks", "resolving flooding" became the top priority, above both traffic congestion and environmental pollution.
The report clearly states: "Planning the construction of underground works and underground transport must be synchronized with the ring road, radial and trans-center transport system, combining underground water collection systems, underground water tanks against flooding and pumping stations such as the upper underground level is the transportation system, the lower underground level is the underground water tank" and in particular, researching the construction of a "giant underground tank" system to store rainwater combined with transportation to thoroughly solve flooding. Researching the planning of additional regulating lakes to store water, drain water, and prevent flooding in areas with low ground levels and frequent flooding".
Faced with increasing pressure from reality, Hanoi has chosen a stronger approach: Issuing 10 orders to build urgent flood prevention works, with a total investment of more than 5,500 billion VND, expected to start construction right at the beginning of 2026. This is considered an unprecedented step, showing a change in management thinking: Considering flooding as a form of "urban natural disaster" that needs to be responded to with special mechanisms.
Emergency projects not only focus on dredging and renovating sewers, but also include building regulating lakes, increasing the capacity of pumping stations, supplementing regulating tank systems and completing inter-regional drainage lines. The goal is to basically complete the main items before the 2026 rainy season.
Architect Dao Ngoc Nghiem - Vice Chairman of the Vietnam Urban Planning and Development Association, said that the decision to spend more than 5,500 billion VND this time shows the determination of the government apparatus in directly facing the most difficult "bottlenecks" of the city.
Not only drainage, the projects are also associated with pollution treatment, landscape improvement and infrastructure connection. If done correctly and thoroughly, this could be a turning point for Hanoi's flooding problem" - Mr. Nghiem said.
However, building more underground tanks is highly breakthrough. Recently, the Hanoi Department of Construction is preparing to build 2 underground regulating tanks in the Long Bien area and the Duong Thanh - Bat Dan - Nha Hoa area (Hang Da market).
The advantage of this solution is to take advantage of underground space in the context of increasingly limited land funds, and at the same time help the city proactively regulate rainwater in real time. When it rains heavily, water is collected into tanks; when the rain stops, water will be pumped gradually into the common system, avoiding overload.
From mid-2020, Hanoi piloted the construction of the first underground regulating tunnel in the yard of Ly Thuong Kiet Secondary School (Nguyen Khuyen street). The project was handed over to Hanoi Drainage One Member Limited Liability Company for operation from the end of 2021.
According to people's reflections, the project has shown clear effectiveness. Mr. Luong Dinh Manh (No. 104 Nguyen Khuyen street, Van Mieu - Quoc Tu Giam ward) said that this area is originally a low-lying area, every time it rains heavily, it is often deeply flooded, sometimes flooding lasts for many days before receding. However, in the past 2 years, the flooding situation has basically been overcome.
In fact, during the heavy rain and flood in 2025, when many streets in Hanoi were deeply flooded for many days, the area around Ly Thuong Kiet Secondary School was only flooded for about 1-2 hours and then receded completely. "Before, heavy rain was deep flooding, now the water only rises for a short time and then recedes quickly" - Mr. Manh said.
However, experts also warn: Underground tanks are not "magic wands". If not linked to the overall plan, not connected to river, lake and large pumping station systems, the effectiveness will be very limited.
In the Master Plan of the Capital with a 100-year vision, Hanoi has ambitions to complete underground tanks with a total capacity of up to 125 million cubic meters and a synchronous and modern drainage system by 2045.
Hanoi's efforts show the prospect that Hanoi will no longer have worries about flooding before each rain.
Talking to a reporter from Lao Dong Newspaper, Mr. Nguyen Duc Hung - Director of Hanoi Technical Infrastructure Management Center - said that underground regulating tanks are arranged under flower gardens, squares or roadways, without affecting daily life, traffic and urban landscape above.
According to Mr. Hung, although the construction cost is higher than the open-air regulating lake, this is the optimal solution for the Old Quarter area, where the land fund is limited. The Hanoi Department of Construction has also consulted with Japanese experts in the design and structure of underground reservoirs, affirming that this is a local treatment solution but brings clear efficiency in flood prevention.
Operating mechanism of 2 underground tanks to be built
The Long Bien underground tank project is designed to increase the ability to collect and store temporary rainwater. The rainwater collection pipeline is made of reinforced concrete with dimensions of 1 x 1m, about 230m long, combined with road surface water collection manholes. The underground tank has a capacity of about 1,800m3, allowing to store large amounts of rainwater in a short time.
Along with that, the project to upgrade the existing pumping station by installing two more submersible pumps, increasing the total capacity of the pumping station to about 1,000m3/hour. After the rain ends, water in the tank will be pumped forcibly into the common drainage system, limiting prolonged flooding.
The project to build an underground regulating tank in the Hang Da market area is proposed with a capacity of about 2,500m3, expected to be built on an empty lot in front of the market gate.
The operating principle of the tank is to proactively create a vacant capacity before rain, close the regulating vents to isolate the flooded area, and collect all rainwater from the road surface leading to the tank. After the rain ends, the water in the tank will be pumped forcibly into the common drainage system for about 4 hours, ensuring no overload for the downstream system.
The project also includes the renovation and relocation of some existing sewer lines; building a new box sewer line with dimensions of 1.5 x 1m and more than 500m long on Phung Hung street to increase the collection and drainage capacity of rainwater for the entire central area.
