Hanoi Intensifies Efforts to ‘Rescue’ Infrastructure, Urgently Constructs 12 Retention Ponds to Combat Flooding

Could you provide an update on the current flooding situation and the city’s drainage system capacity?

In recent years, climate change has led to heavy rainfall, causing widespread and prolonged flooding in Hanoi. This has resulted in severe consequences, including traffic paralysis, vehicle damage, disrupted lives, isolated communities, and significant property and economic losses.

Between August 25 and October 8, three consecutive storms caused heavy rainfall, leading to extensive flooding in the city. In some areas, rainfall exceeded 500-600mm/2 days, nearly 200% of the drainage system’s design capacity (310mm/2 days), resulting in localized flooding.

Additionally, heavy rain raised water levels in Hanoi’s outlying rivers above alarm levels. The water level on the Nhue River at Thanh Liet reached +5.7 to +5.9m, exceeding the planned control level of +4.5m. Meanwhile, the ground level in some urban areas and residential districts in the Left Nhue and Right Nhue basins is only +5 to +5.5m. This situation has made gravity-based drainage nearly impossible, causing widespread and prolonged flooding in low-lying areas.

Hanoi’s drainage system is currently being implemented according to the Capital Drainage Plan until 2030, with a vision for 2050 (Decision 725/QĐ-TTg dated May 10, 2013). Through various projects, particularly the Hanoi Drainage Project Phase 1 and 2, the infrastructure in the To Lich River basin (covering approximately 77.5 km² in four inner-city districts) has been largely synchronized.

However, with the current infrastructure, the drainage capacity in the old inner-city districts can only handle rainfall of 310mm/2 days and above 200mm/day, with a 10-year recurrence cycle. For rainfall up to 50mm/hour, no flooding occurs in the city. However, for rainfall exceeding 50mm/hour, the city experiences flooding in 11 to over 100 locations, as seen during the recent Storm No. 10 (Bualoi).

In the western and southern areas along the Nhue River, drainage infrastructure is being developed according to the plan. Drainage primarily relies on agricultural drainage systems, including pumping stations, canals, and rivers.

Given this situation, what measures will the city and the Department of Construction take to address flooding, especially in the southwestern area?

According to the plan, drainage in Hanoi is divided into three main regions: the Left Day, Right Day, and North Hanoi, with 45 drainage hubs and a total pumping capacity of 1,325 m³/s. The completed drainage system will include pumping stations, urban drainage stations, regulating lakes, and drainage canals and rivers.

While the city and relevant departments have made efforts, the investment in drainage infrastructure has lagged significantly behind urban development.

Currently, only 11 drainage hubs are operational, including Yen So, Co Nhue, Dong Bong 1, Dong Bong 2, Bac Thang Long-Van Tri, and Yen Nghia, representing 20% of the planned capacity. The regulating lake system covers approximately 1,010 ha, compared to the planned 5,405 ha, achieving 18.7%.

The urban drainage canal, river, and sewer system is synchronized only in the To Lich River basin. The Left Nhue, Right Nhue, and Long Bien basins are in the preparation phase for investment. In new urban areas, drainage systems are planned but not yet synchronized with the city’s overall drainage infrastructure, including both drainage systems and ground levels.

To implement the plan and address the current complex flooding situation, the Department of Construction has developed both short-term and long-term solutions.

In the short term, the Department of Construction will expedite the ground level and urban drainage plan, complete the localized flooding control plan for the inner city, and propose six key measures to the City People’s Committee. These measures focus on addressing flooding in the To Lich River basin (four inner-city districts) by improving drainage capacity in the To Lich, Lu, Set, and Kim Nguu rivers, increasing the capacity of existing regulating lakes, and adding local flood control infrastructure (including reservoirs, pumping stations, and connecting sewers).

The Department will also address flooding in heavily affected residential areas such as Thang Long Avenue, Resco, Ciputra, Vo Chi Cong, Ngoai Giao Doan, Tay Ho Tay, Long Bien, Gia Lam, and Dong Anh. Solutions include directing drainage to the To Lich, Nhue, and Red rivers.

Additionally, the city will complete drainage hubs for the Nhue River to the Red and Day rivers, enhance connectivity to the Nhue River, and increase capacity at the Yen Nghia pumping station and the Lien Mac hub.

For long-term solutions, the Department of Construction is finalizing the Localized Flooding Control Plan, expected to be submitted to the City People’s Committee for approval in Q4/2025. This plan accounts for rainfall exceeding the current drainage capacity and accelerates local flood control projects, aligned with the Hanoi Ground Level and Drainage Plan until 2045, with a vision for 2065, considering climate change and rainfall above 310mm/2 days.

The city will construct 12 new regulating lakes and expand existing ones to increase water storage capacity. These lakes include Co Nhue 1, Co Nhue 2, Chem, Lien Mac, Thuy Phuong, Phu Do, Dong Bong 2, Yen Nghia, and the central lake in Ha Dong District. These projects will be implemented urgently to reduce urban flooding.

What are the causes of severe flooding in western urban areas, and what solutions does the Department propose?

Following recent flooding, the Department of Construction and relevant units have inspected urban areas lacking drainage connections to the city’s infrastructure and local pumping stations. Developers in these areas have been instructed to complete canal and sewer systems and invest in internal pumping stations. The Department has also directed immediate flooding control measures for each urban area.

Specifically, in the Vo Chi Cong area, drainage will be directed to Tay Ho Tay, increasing capacity toward Ngoai Giao Doan. In Ciputra, measures include lowering the lake water level to 4.0m and pumping water from residential areas.

In Resco and Ecohome (Dong Ngac Ward), the Thuy Phuong canal has been connected to the Nong Lam sewer, with water pumped directly to the Nhue River. In urban areas along Thang Long Avenue, agricultural canals T3A and T3B will be dredged, and the Dong Tep pumping station will be completed to drain water to the Cau Nga River.

With these synchronized and determined measures, we are confident that Hanoi’s flooding situation will significantly improve in the near future.

Thank you very much!