Some land areas in South Sai Gon as well as canals and tributaries in the outskirts of HCM City have been improperly filled, causing flooding in many areas in the city, according to the Institute of Environmental Management and Science and Technology.
In HCM City, the high demand for land to build infrastructure and new urban areas has led to the filling of these waterways, with 2,600ha already filled over the years to build the South Sai Gon urban zone in the Phu My Hung area.
In addition, more than 6,300ha of land have been used to build industrial parks and more than 10,000ha of agricultural land for new houses.
As a result, upstream river water is causing widespread floods in the inner city, according to the Institute of Environment Management and Science and Technology.
According to local authorities, from 1990 to 2009, many businesses and individuals have filled hundreds of hectares of waterways to develop real estate projects without proper planning.
Cau Son and Van Thanh waterways in Binh Thanh District, Ba Mien in Go Vap District and Nhieu Loc – Thi Nghe have been narrowed, slowing down stream flow and drainage.
Many experts also claim that increased flooding is due to global warming, which has raised temperatures and sea levels.
However, recent research shows that the sea level of Vung Tau from 1990 to 2007 has remained relatively stable, while the water level of Sai Gon River at Phu An area has risen nearly two times, or 1.45 centimetres per year, and in Nha Be District, 1.17 cm per year.
City authorities say that the number of flooding incidents as well as volume of floods and flood-prone areas have increased dramatically in recent years.
In 1980, 10 spots in the city periodically flooded, while today that number has increased to 200.
As for flood intensity, before 1999 the highest tide at Phu An station was reported at 1.36 metres and occurred twice a year.
But now, the highest tide is reported at between 1.42 m and 1.5 m.
In 2008 and 2009, the highest tide in the last 50 years, which lasted for six consecutive days, was reported at between 1.54 m and 1.56 m, causing flooding of more than 100 streets with water level from 20 to 55 cm, or even 80 cm on some streets.
Floods have affected 154 out of 322 wards or communes, leaving 11,000ha of land fallow, affecting millions of people.
At National Highway 13, the Thanh Da residential area, street D2, Van Thanh area, and An Phu, An Khanh and Hiep Binh Chanh villa areas, as well as Districts 4 and 8, thousands of houses are about one metre lower than the street level, leaving them vulnerable to flooding and pollution.
If no effective measures are taken, the volume of flooding will increase, according to Le Huy Ba, head of the institute.
The city authority has asked localities to make detailed analysis of the proper use of urban land.
Lands planned for new residential areas and public works must be strictly under supervision, it has said.
In addition, authorities should recover the natural streams, ponds and lakes within and outside the city in order to reduce the number of floods, the institute said.