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Flooding in the coastal city of Da Nang: What is the solution?

Báo Tài nguyên Môi trườngBáo Tài nguyên Môi trường09/11/2023


Why does it flood every time it rains?

In October 2022, Da Nang experienced a historic flood, with nearly 70,000 houses in the city flooded, thousands of cars and motorbikes damaged, and total material damage after the flood was nearly 1,500 billion VND. Exactly 1 year later, Da Nang suffered another prolonged heavy rain and hundreds of flooded areas occurred throughout the city. Although the level of flooding was not as high as in 2022 and the damage was limited due to proactive response by the people, the situation has highlighted the shortcomings in this coastal city.

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The residential area on Me Suot Street is often flooded during heavy rains.

“In addition to unclogging the sewers, it is necessary to consider appropriate planning, calculate the aperture for the collection gates and raise people's awareness of disposing of garbage in the right place. Because when it rains, just one plastic bag can block an entire water collection gate. People in some places have not proactively unclog when it rains heavily but wait for local forces.”

Mr. Le Quang Nam - Vice Chairman of Da Nang City People's Committee

Analyzing the reason why urban areas are flooded every time there is heavy rain, the Department of Construction of Da Nang City said that the frequency of heavy rains is increasing, exceeding the capacity of the existing drainage system. Most of the drainage systems were built a long time ago and are now degraded. Some sewers were built during the French and American periods with arched brick sewers and later built with rubble, and have collapsed and become clogged.

According to the Department of Construction of Da Nang City, the current sewer system in the area is nearly 1,800km long and nearly 30km of open canals. Of which, about 40km of sewers were built before 1994, using rubble covered with reinforced concrete panels.

For some areas that often experience deep flooding such as Me Suot and Khe Can streets, the Da Nang Department of Construction said that these are areas where people illegally build houses on agricultural land, without proper planning, technical infrastructure cannot be invested synchronously, some areas do not have drainage systems and have low-lying terrain.

Dr. Le Hung (Lecturer of the Faculty of Hydraulic Construction - Da Nang University of Technology) also pointed out that the causes of flooding in Da Nang in recent times are that too many traffic routes such as Da Nang - Quang Ngai Expressway, Hoa Phuoc - Hoa Khuong, Western beltway... have not carefully considered the issue of flood drainage, leading to the number of culverts being arranged still being limited, obstructing the flow and many areas being deeply flooded.

“In the central area, the arrangement of drainage culverts leading too far, the division of water catchment basins is not really reasonable, causing many areas to be overloaded such as Phu Loc River, the water level near the river mouth is still very high even though the tide is very low, this reduces the drainage capacity of the culverts flowing into Phu Loc River.

In addition, the city has too few main drainage axes leading to river mouths and the sea, leading to increasing local flooding, as the water permeability coefficient is decreasing due to the urbanization process," Dr. Le Hung explained.

Overcoming flooding in the short and long term

After the flooding in mid-October 2023, the city directed the Department of Construction, the Drainage Company and project management boards to review all causes and dissect the shortcomings leading to the flooding. Currently, the authorities are focusing on immediate solutions to improve the capacity of the drainage system to bring surface rainwater down to the sewers as quickly as possible. Deal with blockages in the collection pits and garbage blocking the sewers.

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Besides extreme rain, inadequate infrastructure is also the cause of flooding in Da Nang.

In the long term, the city is implementing a project to plan ground elevation and drainage. It is expected that by December 2023, it will assess the existing drainage systems and propose fundamental solutions to handle this situation. The City People's Committee has also directed the Management Board of Priority Infrastructure Investment Projects and the units organizing the zoning planning, in which priority must be given to allocating land to arrange flood drainage corridors and form regulating lakes.

According to experts and scientists, to gradually solve the problem of widespread urban flooding, Da Nang City needs to expand and arrange more discharge gates to rivers such as at Ha Khe to the sea, Da Co bridge, discharge gate from Tran Thi Ly bridge to Asia park... It is necessary to divide drainage zones according to basins reasonably. It can be seen that leading rainwater from Le Thanh Nghi, Nguyen Huu Tho and 30/4 streets to Do Xu canal and then to Cam Le river is too far, not to mention leading from low-elevation areas to high-elevation areas.

It is necessary to consider re-processing the discharge gates to avoid bottlenecks. Although the upstream sewer system has the ability to drain, it is congested at the discharge gates, leading to flooding, such as at the intake gates of Ong Ich Khiem pumping station, Thuan Phuoc pumping station, etc. The stagnant water cannot flow to the suction tank in time, so the pump cannot operate at full capacity.

“An extremely important non-structural solution is to build an urban flood map corresponding to 3-5 levels of rainfall, a map of directions to avoid flooded areas; train and disseminate to each household to download weather forecasting software. Currently, these software forecasts are very accurate and detailed, people can monitor rainfall, clouds, time of rain ending... to proactively respond” - Dr. Le Hung proposed.



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