Rapid urbanisation and excessive exploitation of underground water have led to an alarming land-surface subsidence in many districts around Ho Chi Minh City, a local scientist raised a warning on Wednesday.

A subsiding street in Ho Chi Minh City.

Professor Le Van Trung, director of the Geomatics Center of the Vietnam National University of Ho Chi Minh City, told a seminar here that the pace of land sinking has recently accelerated due to rapid urbanisation and unchecked exploitation of underground water.

Areas vulnerable to land-surface subsidence include Thu Duc and Binh Chanh districts, as well as districts 6, 7, and 8 with an average sinking rate of over 10 millimeters a year, he said.

Trung gave this warning after he had spent 18 months to conduct a VND10-billion project using Dynamic Interferometric Synthetic Aperture Radar, or Insar technology, to detect and measure the ground surface deformation around the city.

“Some streets such as Kha Van Can in Thu Duc District, Vinh Loc B in Binh Chanh District, Ton That Thuyen and Ly Chieu Hoang in District 6 and other areas south of the city have subsided by 0.3 meter since 2000,” he said.

The professor said the easily-seen consequence of land sinking was an increase in flooding sites around the city and that “79 out of 116 flooding sites in the city are the direct consequence of quick sinking of the land surface.”

“We all know that under the impacts of climate change, sea level is forecast to rise by 0.7 meter by 2100, while the land surface in Ho Chi Minh City has been subsiding by at least 10 millimeters a year. Consequently, 60% of the total area of the city could expectedly be submerged under the seawater by that time if we don’t take quick measures to cope with the matter,” he warned.

While housing development as a factor shows no signs of deceleration, enterprises at most industrial parks are drilling deeper to pump underground water for their production, which will aggravate land sinking, experts said at the event.

Trung said that to ensure a safe level of land subsidence by under 5 millimeters a year, the city needed to cooperate with other nearby provinces including Dong Nai, Binh Duong and Long An to effectively contain the exploitation of underground water.