Da Nang searching for urban flooding solutions

On the evening of September 10, after receiving 100 mm of rainfall in two hours, several areas and roads in the city center, including Le Duan, Hung Vuong and Ham Nghi streets, were heavily flooded, with some sections submerged in 0.5- 0.7 m of floodwaters.

Hundreds of cars stalled along the road and had to be towed home, leaving traffic in chaos.

Motorcyclists wade through waters as the street is flooded following heavy rains in Da Nang City on September 10, 2023. Photo by VnExpress/Nguyen Dong

According to the Department of Construction, with Da Nang’s location along the Han River and the coast and a natural area of only 1,285 sq.km, the city should in theory not suffer chronic flooding.

However, Vietnam’s central hub is currently home to at least nine flood-prone regions that become inundated during every extreme rain.

In October last year, Da Nang experienced a historic flooding that inundated the entire city under 1.5 m of floodwaters after it received 795 mm of rain overnight following storm Son Ca. The floods killed four people, and caused more than 200,000 households to lose power.

On September 12, representatives of the Department of Construction and the Da Nang Drainage and Wastewater Treatment Company inspected sewers at the intersection of Hoang Hoa Tham and Le Duan streets in Thanh Khe District to find new causes of flooding.

Vo Tan Ha, the department’s deputy director, said the area is high above sea level and has more than 120 sewer gates on the two streets, both of which have been recently upgraded so "it is hard to understand" why the area is still flooded every time it rains heavily.

Garbage blocks a sewer gate on Hoang Hoa Tham Street, September 2023. Photo by VnExpress/Nguyen Dong

As pointed out by the departments of construction and natural resources and the environment, the city’s drainage system was built more than 25 years ago, and now heavy rains have exceeded the system’s capacity.

Meanwhile, Danang has witnessed a rapid increase in urbanization.

More concrete buildings going up means more impervious surface area, resulting in excessive runoffs, as there is not enough soil left to absorb the water.

In addition, urbanization has been accompanied by an increase in urban population and an increase in the amount of urban waste, which has led to a situation of garbage clogging the drainage system.

A neighborhood in Da Nang's Thanh Khe District is flooded on September 10, 2023. Photo by VnExpress/Nguyen Dong

Deputy director Ha of the Construction Department said that in addition to the flooding point at the intersection of the two aforementioned streets, the department has counted about nine other spots across the city that regularly suffer chronic flooding.

He said the main reason for flooding at most of those spots is the delay of sewer construction following site clearance issues or the lack of funds.

"We will coordinate with the authorities of each district and related units to review all flooded areas to and propose solutions to step by step solve the fundamental problem of urban flooding in the city," said Ha.

According to the department, immediate solutions include dredging and clearing the flow in canals to allow maximum drainage, arranging permanent staff at anti-flooding pumping stations when floodwater rises, and make mobile pumps available to drain floodwaters at low-lying residential areas.