MOC has sent a document to the An Giang provincial NA delegation to answer the questions of National Assembly Deputy Hoang Huu Chien about urban flooding, especially in Hanoi during the Matmo storm.

The ministry stated that large-scale urban flooding stems from multiple causes, including natural conditions, climate change, rising sea levels, outdated planning, weak drainage systems, and lack of investment.

Most urban areas in Vietnam are located in low-lying delta regions near the sea and rivers, where natural slopes are small and gravity drainage is weak. 

Extreme weather events have become more frequent and intense, with prolonged heavy rains exceeding the designed frequency of urban drainage systems. Rising sea levels (high tides) and upstream floods have also worsened flooding.

In Hanoi, the drainage system is still being upgraded according to the 2013 plan, designed for 310mm of rain over two days. However, during Bualoi and Matmo storms, rainfall reached 500mm in less than a day, far beyond the system’s capacity, causing both local and widespread flooding.

The ministry also admitted that the drainage network has not kept pace with urbanization.

By the end of 2024, Vietnam had about 900 urban areas, including more than 200 classified as grade IV or higher, over 10 times the number in 1998. However, most drainage systems are old (over 50 years or built during the French colonial period).

Urban drainage systems combine old and new pipelines, but basically still the combined drainage system formed long ago (rainwater and wastewater drain in the same system) so drainage capacity is uneven. Currently, the drainage pipe ratio per capita in Vietnamese urban areas only reaches 0.7m/person, equal to one-third of the world average (2m/person).

Urbanization has also reduced natural water storage areas such as fields, ponds, lakes, and canals, as these have been replaced by concrete surfaces, reducing natural infiltration.

Lack of capital, drainage system planning

According to MOC, currently only six centrally-run cities have established specialized drainage planning and foundation elevation management, but most of these plans were built long ago, not updating climate change factors and urbanization speed.

The remaining provinces and cities integrate drainage content in provincial planning, which is mainly orientational, lacking synchronization and technical data.

Investment resources for drainage remain limited. The ministry said the state budget meets only about 60 percent of the funding needed for drainage system development. Meanwhile, the mechanism for mobilizing investment in society remains ineffective, and public-private partnership (PPP) projects in this sector are almost nonexistent.

Data from the Ministry of Finance shows that Vietnam has signed 336 PPP contracts, mostly in transport, energy, and social infrastructure, with no recent projects related to drainage or wastewater treatment.

Public awareness of drainage system protection also remains low. People frequently dump garbage into canals and lakes, or block drainage inlets, causing blockages and reducing system capacity.

To address flooding, MOC instructed localities to implement both short-term and long-term solutions.

In the short term, local authorities should clear drains, dredge waterways, repair damaged pipelines, operate pumping stations flexibly, and deploy mobile pumps at flood-prone sites. They should also publish lists of lakes, ponds, and wetlands that must not be filled in to prevent flooding.

In the long term, the ministry emphasized integrating drainage planning with land use, transportation, and irrigation plans; reassessing system capacity; prioritizing public investment in drainage; and building regulating works, pumping stations, and reservoirs while replacing old and degraded systems.

Authorities should also define and strictly control base elevation levels for urban areas, ensuring construction projects comply with approved detailed plans, permits, and inspections.

The ministry highlighted the need to promote non-structural solutions, increase water storage capacity, and avoid excessive concrete along rivers and canals to achieve sustainable, climate-adaptive drainage (“slow drainage”).

Additionally, the ministry urged the application of information technology for smart drainage management, flood mapping, early warning systems, and digital databases for system operation.

It is completing the draft Law on Water Supply and Drainage, to be submitted to the government in 2026 and to the National Assembly in 2027, and revising Decree 80/2014 on drainage and wastewater treatment, expected to be submitted by mid-2026.

Hong Khanh