Many areas in HCM City are physically sinking 7-10mm a year and up to over 15mm annually in some places, according to the latest report of the HCM City-based Geo-Information Centre under the HCM City National University.

Depressed land can be visually observed on Nguyen Huu Canh Road. According to the Urban Transport Management Board under the HCM City Department of Transport, the entire road is sunken. Some sections sunk as low as 20-80cm.

Notably, from Thu Thiem bridge to Nguyen Huu Canh overpass, there are some places where depression reaches 1.2m. Parts alongside the water drainage system are also sunken from 20cm to 1.3m.

According to the Ministry of Transport, there are four sunken sites on the 39.8km HCM City-Trung Luong Expressway.

By researching photos taken from satellites of Europe and Japan from October 1992 to March 2010, the Geo-information Centre has proven that land depression in HCM City is very serious.

The areas where there is rapid urbanization the land has sunk over 15mm a year. Since 1992, many places in 14 districts have been subsided from 20-30cm on average.

According to research, the depression started in 1996 and since 2004 it has become even more.

Land depression causes great losses for the city. Experts estimated that HCM City needs to pay 200 billion dong ($10 million) to deal with land depression on Nguyen Huu Canh road only. Moreover, depression can harm or shorten the lifespan of many transportation routes and architectural works.

An expert from the Geo-information Centre remarked that the recent appearance of “dead holes” in HCM City was partly caused by land depression.

The centre’s deputy director Dr. Le Van Trung noted that land depression increases up along with urbanization and the overexploitation of underground water.

According to the HCM City Department of Natural Resources and Environment, the city exploits more than 1 million cubic meters of underground water per day while the supplementary water volume is only 200,000 cubic meters per day. The underground water level is lowering while more large construction projects are built on the surface, causing land depression.

The department suggested that HCM City authorities ban underground water exploitation in some areas but illegal activities are rampant.

Officials from the HCM City Department of Natural Resources and Environment said that residents in new residential areas are not supplied with tapped water so they have to use underground water.

PV