HCM City's sinking accelerating: experts

HCM CITY — An alarming land-surface subsidence has been seen in 14 districts in HCM City, a local scientist said at a seminar on Wednesday.

Dr Le Van Trung, director of the Geomatics Centre of the National University- HCM City, said the pace of the land-surface sinking had accelerated recently due to rapid urbanisation and unchecked exploitation of underground water.

Land surface in many areas had subsided by 20-30cm, and in some places, had sunk by 50cm since 2004.

Some streets such as Kha Van Can in Thu Duc District, Vinh Loc B in Binh Chanh District and, Ton That Thuyet and Ly Chieu Hoang streets in District 6 have subsided by 30cm since 2000.

Areas under land-surface subsidence include districts 6, 7, 8, 9, 11, 12, Tan Phu, Binh Tan, Binh Thanh, Thu Duc, Binh Chanh, Hoc Mon and Nha Be, with a sinking rate of seven to 10mm per year.

"The decrease in underground water due to a massive use of concrete and filling of canals caused by urbanisation and the increasing exploitation of the underground water are major reasons behind the ground surface deformation," said Trung.

Enterprises in most industrial parks in the city are drilling deeper to pump underground water for their production, said experts at the seminar.

Trung added that the problem had led to an increase in flooding sites around the city.

"The rapid land-surface sinking was the main cause that created 79 out of 116 flooding sites in the city," said Trung.

Trung spent 18 months on a project using Dynamic Interferometric Synthetic Aperture Radar, or Insar Technology, to detect and measure the ground surface deformation around the city.

To ensure a safe level of land sinking of under 5mm per year, HCM City authorities should co-operate with neighbouring provinces, including Dong Nai, Binh Duong and Long An to better manage the underground water exploitation, according to Trung. — VNS