Increased risk on Rama II Road due to land subsidence, rising sea levels

Sonthi Kotchawat, an environmental and health expert at the Thai Environment Academic Club, issued the warning on his Facebook page on Sunday following the fatal collapse of a bridge beam at the Dao Khanong toll plaza on the Chalerm Mahanakorn Expressway. 

The accident, which occurred early Saturday, claimed six lives and injured more than 20 others, sparking urgent calls for improved safety measures and stricter oversight of construction contractors.

Sonthi explained that the soft clay soil in the area, formerly a wetland, is susceptible to subsidence at a rate of one to two centimetres per year, with some locations sinking by as much as one to two inches annually. 

He identified Bang Na, Bang Kapi, Min Buri, Rama II Road and Mahachai as high-risk zones for subsidence.

He also pointed out that the sea level at Chulachomklao Fort in Samut Prakan province could rise by 0.39 metres in 2030 and reach up to 1.68 metres by 2100 due to global temperature increases.

This rise, combined with continued soil subsidence, could heighten the risk of flooding and infrastructure instability.

“In the future, if large-scale projects along Rama II Road are completed, the additional weight, ongoing soil subsidence and rising sea levels could potentially cause the collapse of major structures,” Sonthi warned.

He stressed the need for thorough engineering and environmental impact assessments before proceeding with construction, taking into account the growing risks posed by climate change. 

Similar incidents could occur in other projects built on former wetland areas, he added.

Currently, three major construction projects are underway along Rama II Road:

• The elevated section of Highway 35 (Thonburi-Pak Tho route) from Bang Khun Thian Interchange to Ekachai
• The Motorway 82 elevated route from Bang Khun Thian to Ban Phaeo (Ekachai-Ban Phaeo section)
• The Rama III-Dao Khanong-Western Outer Ring Expressway

Sonthi emphasised that these projects must be closely monitored for land subsidence and sea level rise to ensure the safety of motorists and prevent future disasters.