Long-drawn urban planning issues blamed for Hanoi flooding

By Vo Hai, Son Ha   May 31, 2022 | 08:15 pm PT
Long-drawn urban planning issues blamed for Hanoi flooding
A section of Hanoi's Nguyen Trai Street is flooded after heavy downpours, May 29, 2022. Photo by VnExpress/Ngoc Thanh
Insufficient water drainage capacity, disappearing lakes and poor urban planning are the chief reasons for flooding in Hanoi during heavy downpours.

On Sunday and Monday over 80 spots were inundated following incessant rains, paralyzing traffic all over the city. As the rising water invaded homes and turned lives upside down, authorities and policymakers scratched their heads trying to figure out why Hanoi is so vulnerable to flooding when it rains.

Historic rain levels

Over two hours in the afternoon last Sunday, weather stations on Lang Street in Dong Da District recorded 138 mm of rain, or 6 mm higher than the previous record of 132.5 mm in 1986, according to the National Center for Hydro-Meteorological Forecasting.

There were places with even higher precipitation like Tay Ho District (150 mm) and Cau Giay District (170 mm).

The 170 mm of rain recorded in two hours in Cau Giay is considered to be the highest ever recorded in Hanoi, the center said, adding such rains come only once every 100 years.

Trinh Ngoc Son, deputy director of the Hanoi Drainage Company, said the historic levels of rainfall overloaded the city's drainage capacity.

Certain locations in the west like Keangnam building and Phan Van Truong Street only saw water recede after 10 p.m.

"Even developed countries do not have the financial capacity to design a water drainage system that can handle such a large amount of water," Son said.

Minister of Natural Resources and the Environment Tran Hong Ha said global warming is triggering extreme weather events.

"If heavy rains are concentrated in a short amount of time, no infrastructure can cope."

Unsynchronized drainage systems

Hanoi has 29 districts and one town, with 12 inner districts spanning 250 sq.km.

The drainage basin of the To Lich River, spanning 77.5 sq.km, covers all of Ba Dinh, Hoan Kiem, Dong Da, Hai Ba Trung, and Hoang Mai districts, and part of Tay Ho and Thanh Xuan districts.

It can drain 310 mm of rain in two days, but intense downpours can cause inundations.

The 110-sq.km drainage basin of the Nhue River spreads over Cau Giay, Thanh Xuan, Hoang Mai, Nam Tu Liem, Bac Tu Liem, and Ha Dong districts and parts of Tay Ho and Thanh Tri. It has a high urbanization rate but modest drainage capacity, lacks reservoirs and its key pumps have not yet reached their designed capacity.

In the Long Bien River basin, rainwater drains naturally by flowing into the Nam Stream, Tam Dau channel and Cau Bay River, and the Dong Tru pump station directs it into the Duong River.

In the rest of the city, sewers carry the water into surrounding fields and lakes. Thanks to a large number of lakes and ponds, flooding is rare in these areas.

Nguyen The Cong, deputy director of the city Department of Construction, said the drainage system is only synchronized in inner districts.

Ha Dong, Long Bien, Bac Tu Liem, and Nam Tu Liem districts have however yet to see investment in drainage construction, meaning they can be flooded if it rains heavily enough.

Cong said the capital plans to synchronize its pumping and drainage systems, but that requires a lot of money and so could take five or 10 years.

Investment, planning issues

Vu Trong Hong, the former agriculture and rural development minister, said in several downtown areas, the drainage systems have been there since the French colonial era, meaning they are outdated and cannot satisfy today's urban requirements.

Due to lack of funds for upgrading the drainage system, the same spots in downtown areas keep getting flooded year after year, he said.

There are new flooding spots in outer districts like Cau Giay, Ha Dong, Bac Tu Liem and Nam Tu Liem now, which are all developing areas with quick population growth and urbanization rates, Hong said.

Pham Thanh Tung, head of the Vietnam Association of Architects office, said Hanoi has invested in its water drainage network in the last couple of years, but the results are unclear.

The city has limited resources but too many projects, and the construction of pumping stations and drainage systems simply could not keep abreast of its urbanization rate, and this combined with the effects of climate change results in inundation, he said.

Hoang Van Cuong, vice principal of the National Economics University, said one of the reasons for Hanoi’s flooding is the overlap in planning by various agencies.

Homes and other urban structures are built without consideration for water drainage systems that are needed, he explained.

"According to the 2017 Law on Planning, the construction of infrastructure, irrigation and agriculture structures should be synchronized.

"If we do this right, big cities like Hanoi could solve their flooding issues."

Nguyen Van Lien, the former deputy construction minister, too said urban development without paying attention to water supply and drainage is the reason why flooding happens year after year.

Disappearing lakes, trees

Lien also expressed concern over the relentless decrease in water bodies and green cover in Hanoi.

As more and more concrete is used, water finds it difficult to percolate into the soil and naturally flows to lower areas, creating inundation, he said.

"Hanoi is lower at its center, and that is always the most severely inundated area."

The capital has yet to announce official statistics with respect to encroachment into ponds and lakes, but a report by the Center for Environment and Community Research said 17 lakes in the downtown area have completely disappeared while only seven new ones were created. The total water surface area reduced as a result from 2,100 ha before 2010 to just 1,165 ha in 2015.

Lien said one solution is to enlarge lakes, ponds and grass fields in downtown Hanoi so that there is enough space for water to drain.

The city also needs to complete its drainage and pumping station works and synchronize the water drainage network in new areas.

Tung said Hanoi could learn from anti-flooding strategies adopted by cities around the world such as by building underground reservoirs.

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