Expressway builder, local authorities disagree on cause of flooding

A 100-m section of the Dau Giay – Phan Thiet Expressway in Binh Thuan Province was flooded early Saturday following heavy rainfall, leaving vehicles stranded for five hours.

At around 2 a.m. there was no way for the water to drain on either side and began instead to flood a low-lying section of the expressway, which opened to traffic in late April.

Some places were under a meter of water.

Hundreds of vehicles were stuck on either side of the flooded section. The water started to recede at dawn, but some areas remained under half a meter of water and only vehicles with high clearance could traverse them.

A section of Dau Giay - Phan Thiet Expressway is under floodwaters on the morning of July 29, 2023. Photo by VnExpress/Tu Huynh

Dang Hung Thai, director of the project management board, said water had flowed into the low-lying area of the expressway from three different directions and a river nearby was overflowing.

"Therefore it is necessary to dredge the downstream parts of waterways," he said at a meeting on Monday.

He was responding to local authorities, who questioned the project's design and drainage capability.

Thai said the Ministry of Transport’s Thang Long Project Management Board, which built the expressway, and the Transport Engineering Consulting Joint Stock Company No. 533, its consultant, are reviewing the topography and hydrology in the vicinity of the flooded section to assess the situation.

A representative of the latter said the section was designed based on available hydrological and topographic data.

He said the expressway was flooded due to excessive rainfall.

He also said that there are a lot of plants along the sides of the river near the expressway, obstructing the flow of water.

But Binh Thuan authorities dismissed his claims.

Trac Xuan Cuong, deputy chairman of Ham Tan District, where the flooding occurred, said "those reasons are not accurate."

He said the plants along the river should not have anything to do with the water flow, and no one has built any structure to block the flow.

Local authorities believe that the flooded expressway section was built too low, and that this could be the cause of the flooding, and so it is necessary to reassess the design, he said.

The Binh Thuan Department of Agriculture and Rural Development said the section only has one sewer measuring 2.5 m wide and 2.5 m high, described it as "small" and called for enlarging it in preparation for more heavy rains.

The location where flooding occured on the Dau Giay - Phan Thiet Expressway has one culvert. Photo by VnExpress/Viet Quoc

Huynh Ngoc Thanh, deputy director of the province Department of Transport, said the section should not have been so low or unnecessarily steep.

The project management board and consultant were not able to come up with a specific reason for the flooding and how to mitigate it in future.

Running 99 km through Dong Nai and Binh Thuan provinces, Dau Giay - Phan Thiet Expressway links up with the Ho Chi Minh City – Long Thanh – Dau Giay Expressway between HCMC and Dong Nai.

It enables vehicles to cover the 177-km distance between HCMC and Phan Thiet, known for its beaches and sand dunes, in a little more than two hours as against six hours earlier.