Between the night of September 16 and the morning of September 17, Vietnam's Hanoi experienced heavy rainfall, with flooding spreading throughout the city.
Some roads submerged nearly 1 meter deep, and several schools advised parents to pick up students early.
Despite Hanoi's recent drainage facility construction, why does flooding keep recurring?
Three-Line Summary
1. Hanoi flooded again on September 16–17 from heavy rain
2. The Yên Sở area received 270mm and 200mm of rain over two days
3. Caution for heavy rain is needed until drainage facilities are completed
September 16–17: Roads Flooded Again
Between the night of September 16 and the morning of September 17, rainfall exceeding 150mm per hour poured down on Vietnam's Hanoi. According to VnExpress reporting, the Cầu Diễn area in western Hanoi (where National Route 32 passes through) submerged nearly 50cm deep, paralyzing traffic in both directions, with people pushing stalled vehicles by hand. Cầu Cốc Street in the Tây Mỗ area had flooding depths approaching 1 meter, forcing residents to travel by boat. The Ring Road 3 Phạm Văn Đồng section experienced traffic congestion extending several kilometers.
As rainwater continued to accumulate, several schools in Hanoi advanced dismissal time on the afternoon of the 17th. According to Kenh14 reporting, Tân Xuân Middle School notified parents they could pick up children from 3:30 p.m., and Nguyễn Siêu Elementary School from 2:15 p.m., while some elementary schools closed entirely or switched to online classes. Hanoi's Department of Education and Training instructed schools to continuously monitor weather conditions and refrain from outdoor activities in areas at risk of flooding or landslides.
Yên Sở: 270mm—Nearly Double the Design Standard
According to Dân Trí reporting, Hanoi's drainage system was designed to withstand 310mm of rain over two days. However, between the night of the 14th and the 15th, the Yên Sở area (a low-lying region in southern Hanoi) received 270.4mm of rainfall, and between the night of the 16th and the morning of the 17th, nearly 200mm of rain fell again depending on location. During last year's monsoon season, typhoon influence brought 500–600mm of rain to Hanoi, resulting in flooding at approximately 220 locations.
In response, Hanoi launched 10 emergency projects, including 5 retention ponds and 5 drainage initiatives. According to Hanoi's Department of Construction, these projects directly affected approximately 120 flooding points, with water draining faster than before in some areas. However, the Construction Department itself acknowledged that this scale of work cannot prevent citywide flooding.
Copenhagen, Rotterdam, and Singapore Contain Rainwater
Dân Trí highlighted three foreign cities as references for Hanoi. Denmark's capital Copenhagen suffered approximately 50–60 billion kroner (about 2 trillion and 4000 hundred-million won) in damage from 150mm of rainfall in just two hours in July 2011, after which it designed a plan to redesign roads, parks, and plazas as spaces where rainwater could temporarily accumulate rather than expanding sewer pipes. Rotterdam's Benthemplein plaza in the Netherlands normally serves as a recreation area, but during heavy rain collects approximately 170万 liters of water accumulated from its roof and surroundings into three retention basins. Singapore established this by law, requiring development sites of 0.2 hectares (2000 m²) or larger to have facilities that delay runoff to prevent rainwater from rushing into sewers all at once.
A Dân Trí column cited the Intergovernmental Panel on Climate Change (IPCC), reporting that maximum daily precipitation can intensify by approximately 7% for each 1-degree rise in Earth's average temperature. The reduction of lakes and low-lying areas in cities through landfill, which reduces land where rainwater can seep in, is also cited as a factor exacerbating flooding. Hanoi now faces a moment where it must consider not just expanding drainage pipes but also where to hold rainwater.