Surface concretization a major reason for unprecedented flooding in Danang

Surface concretization was a major reason behind the recent unprecedented flooding in the central city of Danang, says architect Ngo Viet Nam Son, head of NgoViet Architects & Planners.

The historical flooding following torrential rains from October 13-15 inundated the entire Danang city, with some places under almost two meters of water.

Besides the heavy rains and poor drainage infrastructure, rapid urbanization was also blamed for the severe flooding. Apart from inner-city districts, surface concretization has now spread to the city’s western mountainous areas.

As a coastal city, Danang is forecast to face even more heavy rains in the future as a result of climate change, sea level rise, and high urban density. Therefore, the city needs to prepare plans to effectively respond to more extreme rains.

First, it should increase green spaces in inner-city areas and develop green belts (forests) in hilly areas bordering plains to retain water and slow down the water flow from the mountains.

Danang must develop more parks as its current park area is quite low. Land at parks plays a significant role in absorbing water to help reduce flooding and saltwater intrusion.

The city also needs to build more canals and reservoirs, even underground ones, to collect water.

Danang should gradually improve and upgrade the drainage infrastructure in old, existing urban areas and closely monitor the construction of modern drainage systems in new ones.

There is also need to zone off urban areas in high-enough localities to minimize future impacts from climate change and sea level rise.

According to the Danang People's Committee, total losses caused by the historical flooding following torrential rains from October 13-15 were estimated at VND1.5 trillion ($60.31 million). Lien Chieu district was hardest hit with VND578 billion ($23.24 million) in damage, followed by Hoa Vang district VND250 billion.

Floods damaged the property of most families and many schools were submerged in mud. It was estimated that more than 2,000 cars and over 30,000 motorbikes suffered engine damage caused by floods.

Director of the municipal Department of Construction Phung Phu Phong said the historical rainfall on October 14, reaching up to 700 millimeters, exceeded the capacity of Danang’s drainage system, which is able to cope with rainfall of 100-200 millimeters.

Phong noted that during the incident, some pumping stations in the city lost power. However, power supply for pumping stations in the case of urban flooding had not been included in the city’s disaster response scenario. The huge water flow from the 820-hectare Danang International Airport was also a cause of flooding, he added.