According to the Ministry of Construction, Hanoi’s drainage infrastructure remains based on a plan drafted in 2013, designed to handle only 310mm of rainfall over two days. In reality, the city recently faced nearly 500mm of rain in under 24 hours, resulting in widespread flooding.

Outdated infrastructure

The Ministry of Construction has issued an official response to a query from National Assembly delegate Hoang Huu Chien of An Giang province regarding severe urban flooding, particularly in Hanoi following Storm No. 11.

The ministry pointed out multiple causes for widespread flooding in urban areas. These include natural conditions, climate change, rising sea levels, outdated urban planning, weak drainage systems, and a lack of investment.

Most Vietnamese cities are located on low-lying plains near the sea or rivers, with minimal natural slope and limited gravitational drainage capacity. Extreme weather events are becoming more frequent, with prolonged heavy rainfall exceeding the design thresholds of current drainage systems. Coupled with rising sea levels and upstream flooding, these factors are contributing to widespread inundation.

In Hanoi, the drainage system has not been comprehensively upgraded and is still undergoing improvements based on a 2013 master plan. That plan accounted for just 310mm of rain across two days. However, after Storms No. 10 and 11, the city experienced nearly 500mm of rain within a single day, far exceeding design capacity and resulting in both localized and large-scale flooding.

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A residential building in Hanoi was isolated by floodwaters after a storm in August 2025. Photo: T.T

In addition, the Ministry acknowledged that sewer networks have failed to keep pace with the city’s rapid urbanization.

By the end of 2024, Vietnam had around 900 urban centers, including over 200 classified as Level IV or higher - more than 10 times the number in 1998. Still, most drainage systems were built decades ago, some more than 50 years old, with infrastructure dating back to the French colonial era.

Current urban drainage networks are a patchwork of old and new systems. Most areas still rely on combined drainage (stormwater and wastewater in the same pipes), which leads to inconsistent flow and reduced efficiency. The current national average drainage pipeline length per capita is just 0.7 meters, one-third of the global average of 2 meters.

Urbanization has also reduced natural water storage space. Farmlands, open spaces, ponds, lakes, and canals that once absorbed rainwater have been paved over, drastically decreasing the natural infiltration area.

Lack of funding and outdated planning

The Ministry noted that only six centrally governed cities have developed specialized drainage and elevation management plans. Most of these were drafted years ago and have not been updated to reflect current climate change impacts or urban growth.

In other provinces, drainage considerations are included within broader provincial plans, typically offering only directional guidance without technical specificity or integrated data.

Investment in drainage infrastructure is also limited. The state budget currently meets only around 60% of the funding needed for drainage development. Meanwhile, efforts to mobilize private capital through public-private partnerships (PPP) have been largely ineffective.

According to the Ministry of Finance, Vietnam has signed contracts for 336 PPP projects, mostly in transportation, energy, and social infrastructure. There have been almost no PPP investments in urban drainage or wastewater treatment in recent years.

Public awareness of drainage system protection also remains low. Many people still discard trash into drainage ditches and retention lakes, or block water inlets with debris, leading to clogs and reduced capacity.

To address the worsening flood risk, the Ministry of Construction has urged local authorities to implement both immediate and long-term solutions.

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Avoid paving over urban riverbanks and canals to preserve drainage capacity. Photo: Nam Khanh

In the short term, measures include clearing clogged drains, dredging waterways, inspecting and repairing damaged pipelines, operating pumping stations flexibly, and deploying mobile pumps in flood-prone areas. Authorities are also encouraged to publish a list of lakes and ponds that must not be filled to ensure flood mitigation.

In the long run, the Ministry stressed the importance of integrating drainage planning with land use, transportation, and water management. It recommended reassessing system capacity, prioritizing public investment in drainage, building new reservoirs and pumping stations, and replacing outdated infrastructure.

Additionally, cities should identify elevation benchmarks, strictly manage construction heights for new buildings, and enforce regulations through detailed planning approvals and construction permits.

The Ministry also emphasized the need for non-structural solutions. These include expanding water retention areas, promoting natural drainage, and halting the concrete encroachment of riverbanks and canals to support sustainable drainage - also known as “slow drainage” systems.

Other proposals include applying smart technology to manage urban flooding, developing flood risk maps, establishing early warning systems, and building a digital database to support system operations.

The Ministry also revealed plans to finalize the draft Law on Water Supply and Drainage for submission to the government in 2026, with the aim of passing it through the National Assembly by 2027. It is also revising Decree 80/2014 on drainage and wastewater treatment for submission by mid-next year.

Further initiatives include developing policies to support anti-flooding infrastructure in cities, exploring sustainable drainage models like “sponge cities,” and issuing new national technical standards for climate-resilient urban planning.

Hong Khanh