Preventing urban flooding: Need for synchronous and long-term solutions

In early October, the circulation of storms No. 10 and 11 caused prolonged heavy rains, causing the water level of the Lo River to rise, causing serious flooding in many central wards of Ha Giang 1, Ha Giang 2 and Minh Xuan. When the water receded, the amount of garbage and mud left behind caused environmental pollution, clogged sewers, and greatly affected people's lives. This situation raises an urgent need for fundamental solutions to prevent and combat urban flooding, especially in the face of increasingly obvious impacts of climate change.

Current situation

In the early morning of October 1, the Lo River suddenly rose, flooding into residential areas, leaving residents of Ha Giang 1 and Ha Giang 2 wards unable to react. Mr. Nguyen Van Vi, group 8 Quang Trung, Ha Giang 2 ward said: "In all the years I have lived here, I have never seen the river rise so quickly and recede so slowly as in the recent flood. In just one night, the water flooded deep into my house and many other households, all of whom did not have time to move their belongings."

The historic flood caused localized flooding in Ha Giang 1 and Ha Giang 2 wards.

According to data from Tuyen Quang Hydrometeorological Station, on the morning of October 1, the water level of Lo River at Ha Giang station reached more than 106 m, exceeding the alarm level 3 by 2.93 m; while at Bac Quang station, the flood peak was only 72.6 m. Thus, the flooding mainly occurred in the central area of ​​Ha Giang ward. Comrade Do Xuan Phuc, Deputy Director of the Department of Industry and Trade, commented: "Such a large difference in water level is due to stagnant flow, water cannot drain in time, leading to flooding. The cause is due to the dense urbanization process and some downstream works encroaching on the flood escape corridor, narrowing the river surface".

In Minh Xuan ward, the heavy rain on the morning of October 7 with rainfall of over 100 mm caused flooding on many streets in Minh Xuan ward, mainly concentrated in Phan Thiet residential groups 9, 10, 14... According to the reporter's records, the water rose mainly because the sewer system could not drain water in time. After only nearly 3 hours, the water level in some places was nearly 1 meter deep, this is truly an "unprecedented" event. The house of Ms. Nguyen Thi Binh, Phan Thiet residential group 14, was flooded nearly 1 meter deep after only a few hours of heavy rain. Ms. Binh said that in nearly 20 years, her family had never experienced such a situation, many items in the house were completely submerged in water before they could be moved.

The recent rain was a rare extreme event, when the rainfall far exceeded the design and coincided with the time when the rivers were all high. In these cases, it is impossible to "prevent" it completely, but there must be flexible prevention plans and operational backup systems.

Underground sewer infrastructure is not synchronized.

According to comrade Nguyen Xuan Long, Head of the Economic Infrastructure Department of Minh Xuan Ward, the situation of clogged sewers and stagnant water has many causes, but most of them are due to the current underground sewer infrastructure being inconsistent. Most of the sewers are old, damaged, and not regularly maintained, especially to prevent odors. Many households have arbitrarily built sewer covers, so when it rains heavily, fallen leaves will cause the sewers to quickly become clogged and cause flooding.

The street next to the People's Council of Tuyen Quang province is often flooded during heavy rain.

According to the report of the Thanh Tuyen area construction investment project management board, the entire underground and surface sewer system of the old Tuyen Quang city is about 14.7 km long, running along the streets and alleys of residential areas. However, the sewer systems are not synchronized, for example, the surface sewer on Ha Huy Tap street is 0.4 m wide and 0.8 m deep, but the surface sewer in Xuan Hoa area is 1.2 m wide and 1.5 m deep. Next, the surface sewer section on Binh Thuan street is 0.4 m wide and 0.7 m deep, or the underground sewer system running across the street also has completely different widths and depths, some are large, some are small... This is a lack of synchronization in the drainage system in residential areas.

In Ha Giang 1 and Ha Giang 2 wards, the current sewer system still shows many limitations and has not been synchronously connected with the riverside drainage network. Some cross-road sewers have small cross-sections, not meeting the drainage capacity when heavy rains accumulate. In many residential areas and key routes such as Minh Khai Street (provincial Boarding School area), Ma Tim slope, Ly Tu Trong Street and the beginning of Phung Hung Street near the big market..., every time there is heavy rain, flooding often recurs. In fact, the recent flood showed that households, in order to clean up quickly, pushed garbage and mud into the sewers, causing the drainage system to stagnate and slowing down the drainage process. On the other hand, the management and maintenance of the drainage system still has many shortcomings. Ha Giang Urban and Environment Joint Stock Company is the unit directly handling garbage and mud in the system and is currently only assigned the function of collecting and treating surface water. Periodic maintenance and dredging depend on the proposal of local authorities, following the mechanism of "handling where there is congestion", lacking initiative and synchronization.

Mr. Bui Xuan Binh, Chairman of the Board of Directors of Ha Giang Urban and Environment Joint Stock Company, emphasized that many round or small-section sewers without covers are very difficult to access and handle thoroughly, so ensuring drainage according to design is extremely difficult.

Towards safe and sustainable urban areas

Environmental experts warn that climate change is causing extreme rains to increase in both frequency and intensity, exacerbating existing weaknesses in urban infrastructure.

According to data from the Ministry of Agriculture and Environment, heavy rainfall of over 100 mm/hour has increased rapidly over the past 30 years; between 1990 and 2020, the number of extreme rainy days in the North increased by nearly 20%, while average annual rainfall increased by 10-15%. This means that Hanoi and many other urban areas will have to face heavier rains, deeper and longer flooding in the coming years, especially when the drainage system has not been designed to suit new climate scenarios.

Some drainage lines in Ha Giang are still narrow, causing difficulty in drainage during high tide.

Discussing this issue, comrade Ha Minh Man, Chairman of the People's Committee of Ha Giang 2 Ward, said that the ward has directed the heads of residential groups to strengthen propaganda to raise people's awareness of environmental hygiene, not to litter indiscriminately, causing pollution and obstructing the flow. At the same time, warning signs have been put up, strictly prohibiting dumping garbage in sensitive areas such as river banks and near drainage sewers. Currently, the ward has made an estimate to dredge the entire sewer and ditch system in the area, and at the same time expand the water discharge gates to the Lo River in low-lying areas to increase the ability to regulate and drain water.

From 2023 to now, along with the pavement paving process, many drainage ditches in the inner city of Ha Giang (old) have been maintained, contributing to the beautification of the urban landscape. These items mainly focus on the small branch drainage ditch system, with a cross-section of only 60B x 80H, the main sewers remain in their old state, have not been upgraded synchronously, leading to limited drainage efficiency.

Comrade Phung Minh Manh, Deputy Director of the Ha Giang Regional Construction Investment Project Management Board, said that in order to overcome the local flooding situation, in the coming time, the unit will continue to propose to local authorities to synchronously repair and upgrade the sewer and drainage system on key routes such as 19/5 Street, Nguyen Van Linh extension, 20/8 Street and some residential areas that are frequently flooded.

In the center of Minh Xuan ward, to completely resolve the situation of water stagnation during heavy rains, according to Mr. Le Hong Thanh, Chairman of the Board of Directors, Tuyen Quang Urban Management and Environmental Services Joint Stock Company, after receiving the task of handling the surface and underground sewer systems from the Thanh Tuyen Area Investment and Construction Project Management Board, the unit will be determined to complete the work as required, especially quickly overcoming incidents to ensure safety during the rainy and stormy season.

However, in the future, there is still a need for synchronous investment in smart urban infrastructure such as installing sensor systems, flood warning maps and real-time data management software. This solution helps authorities monitor and forecast flooding situations early, proactively plan dredging, drainage and timely response, towards building safer and more sustainable urban areas against natural disasters.

Article and photos: Le Duy - Hoang Ha

Source: https://baotuyenquang.com.vn/xa-hoi/202510/chong-ngap-ung-do-thi-can-giai-phap-dong-bo-va-lau-dai-9f3684d/