Ha Noi urged to adopt ‘sponge city’ model to mitigate flooding

Urbanization challenges

In September and October, consecutive heavy rains inundated many districts of Ha Noi. The Ha Noi Drainage Company reported that rainfall on the night of September 30 alone exceeded 300 millimeters in some areas, submerging streets and paralyzing traffic.

While flooding is not new, each downpour revives the debate over the city's chronic drainage problems. Experts say the issue stems not only from rainfall surpassing the system's design capacity but also from deep-rooted flaws in urban planning and development.

A modern city cannot rely solely on drains, canals, and pumping stations. With most surfaces now covered by concrete, rainwater has nowhere to seep, making flooding after a few hours of heavy rain almost inevitable.

Rapid urbanization has also led to the disappearance of natural lakes, ponds, and canals. Absorbent land has been replaced by impermeable surfaces, and many new urban areas are built on higher ground, leaving surrounding neighborhoods prone to localized flooding.

Former Director of the National Institute of Urban and Rural Planning Ngo Trung Hai said such problems result from fast-paced development that disregards natural systems.

"Ha Noi cannot continue to 'fight floods' after every rainstorm. The city must learn to live with water, minimize damage, and integrate long-term strategies into its planning," Hai said.

He added that adopting the "sponge city" model — an approach used successfully in many countries — could help transform heavy rainfall from a disaster risk into a manageable event.

Despite having many lakes, most in Ha Noi are small, isolated, and disconnected from the main drainage network, reducing their water-retention function. Major rivers such as To Lich, Nhue, and Kim Nguu remain under heavy drainage pressure, highlighting the urgent need to synchronize urban development and drainage planning.

Planning and coordination crucial

Dr. Tran Van Mieu, Vice President of the Viet Nam Association for Nature and Environment Protection, emphasized that about 90 percent of climate-related problems stem from human activity.

"Urban flooding is largely a result of poor coordination and the lack of practical, consistent solutions," Mieu said.

He stressed that planning is the key — particularly the integration of urban and transport planning with underground drainage systems. Mieu suggested developing shared underground corridors that combine drainage, telecommunications, fiber-optic cables, and water supply lines.

"Construction standards must ensure appropriate elevation levels for effective drainage," he added, "while natural waterways within the city must be cleared and maintained." Increasing the permeability of urban surfaces through green spaces, parks, and vegetation is equally essential, he noted.

Given Ha Noi's tropical monsoon climate, experts say heavy rains are unavoidable. Instead of focusing solely on flood prevention, the city should adopt a "living with water" approach — treating water as a natural part of the urban environment to be managed through thoughtful design.

When properly planned, every park, lake, and canal can act as a "water buffer," easing pressure on drainage systems during storms. Experts stress that to end flooding, the city must first improve water retention before expanding drainage networks. Without sufficient storage capacity, even large pipes will only provide short-term relief.

Countries like the Netherlands and Singapore have demonstrated the success of this mindset. The Netherlands, with one-third of its territory below sea level, manages water through flexible dikes, retention lakes, and flood plazas. Singapore designs parks and public squares that double as stormwater reservoirs, improving both drainage and urban aesthetics.

For Ha Noi, "living with water" represents not only a technical solution but also a vision for sustainable urban development. Water surfaces, green spaces, and natural depressions should be regarded as critical infrastructure, on par with roads and power systems.

Toward a resilient and green future

To realize this vision, Ha Noi needs close coordination from master planning to on-the-ground implementation. New urban areas must strictly adhere to drainage basin zoning principles, and land elevation adjustments must be carefully assessed to prevent new developments from worsening flooding elsewhere.

The proportion of green and water surfaces must meet planning standards and should not be reduced to increase construction density. The city should also promote permeable materials and water-absorbing technologies — such as permeable tiles for sidewalks, and underground reservoirs in parks and squares — to temporarily store stormwater and relieve pressure on drainage systems.

In the long term, Ha Noi aims to complete an integrated drainage master plan by 2030, organizing its system into eight main basins connected to lakes, rivers, and pumping stations. Once synchronized, each basin will be able to handle rainfall independently, easing the burden on central districts.

Effective management and maintenance are also essential. Even the most advanced systems degrade without proper upkeep. Canals and drains should be cleared regularly, especially before the rainy season. Public awareness campaigns are equally vital, encouraging citizens not to litter and to help protect the city's drainage network.

Assoc. Prof. Dr. Doan Thu Ha, Director of the Institute of Water Supply, Sewerage and Environment Research, highlighted another urgent issue: wastewater management.

"Ha Noi generates over one million cubic meters of domestic wastewater daily, but less than 30 percent is treated properly," Doan said. "Meanwhile, the city receives 1,600–1,800 millimeters of annual rainfall — most of which flows away instead of being reused."

She added that recycling treated wastewater could provide water for irrigation, street cleaning, and industrial uses while replenishing lakes and reducing flooding. Many countries have successfully linked wastewater treatment with ecological landscape projects, such as retention lakes, rain gardens, and water parks.

"Developing green infrastructure — including ecological lakes, wetland parks, and river corridors — would not only improve water management and pollution control but also enhance urban landscapes and residents' quality of life," Ha emphasized. "This is a vital step toward building a modern city that grows in harmony with nature".

Plan to "Revive" Four Inner-City Rivers of Ha Noi

On 22 July 2025, the "Plan for Environmental Quality Recovery and Development of the system of four inner-city rivers: To Lich, Kim Nguu, Lu, Set was approved. The plan includes 32 programmes/projects to be implemented in the 2025-2030 period. It focuses on pollution prevention & control, building an ecological-balanced urban river system and landscape and architectural improvement of river banks.