CHIANG RAI-The Department of Public Works and Town & Country Planning kicks off a full study to tackle chronic flooding in the Mae Sai border area, with a budget of almost 3 billion baht. Design work is underway, with project completion targeted for 2032. The plan focuses on floodways, permanent flood walls, and new settlement areas for affected residents.
On Friday, at the Piyaporn Pavilion Hotel in Mae Sai district, Chiang Rai province, the Department of Public Works and Town & Country Planning, Ministry of Interior, held the first workshop for a major design and planning project.
The workshop covered the detailed design contract and master plan study for the improvement of the Sai River to increase its drainage capacity in Chiang Rai. Mr Prasong La-orn, Deputy Governor of Chiang Rai, chaired the opening and led representatives from government agencies, local administrative organisations, and related sectors.
Chronic floods in Mae Sai trigger a large-scale study
The department has hired Water Development Consultants Group Co., Ltd. as the project consultant. The firm presented the study framework and key information at the meeting.
Mae Sai district is a key economic gateway that links Thailand with Myanmar and the Greater Mekong Subregion (GMS). Over time, urban growth has pushed into the Sai River corridor , especially into the natural floodway of the river. This encroachment has reduced the river’s capacity and caused frequent flash floods and repeated flooding almost every year.
The most recent major flood hit in September 2024, when about 200 millimetres of rain fell in a short period. The heavy rain triggered flash floods and mudflows that caused damage estimated at over 6 billion baht.
In response, the government allocated funding for the Department of Public Works and Town & Country Planning to carry out a full study and design to solve the problem in a lasting way. The study covers both the border trade checkpoint area and nearby communities.
For the 2025 to 2026 budget years, 23,578,000 baht has been set aside for the study phase.
Study area and technical concept
The study area lies within three municipalities: Wiang Phang Kham subdistrict, Mae Sai subdistrict, and Mae Sai Mittraphap subdistrict. Together, these municipalities cover 56.13 square kilometres.
From this, 10.75 square kilometres have been selected for detailed feasibility assessment and detailed design.
The core concept is to restore and organise the river corridor so that the system can safely pass large volumes of flood water. The main elements include:
- A defined floodway for the Sai River
- Flood protection embankments along the riverbanks
- A more efficient drainage system to handle intense local rainfall
The design target is to allow the system to carry at least 430 cubic metres per second of flow passing over the Mueang Daeng weir near Wat Tham Phajom. This matches the peak flood flow recorded in 2024.
New settlement areas for affected residents
Because permanent flood defences and embankments will require clearance along parts of the riverbank, some residents and buildings will be affected.
The initial plan identifies three potential land plots to relocate or resettle affected households:
- Plot 1, Tobacco Station land at Wiang Phan
- Size: 78 rai, 1 ngan, 72 square wah
- Distance from border: about 2.5 kilometres
- Plot 2, Ministry of Finance land
- Size: about 1,000 rai
- Distance from border: about 7.5 kilometres
- Plot 3, Treasury Department land
- Size: 35 rai
- Distance from border: about 1.5 kilometres
These locations will be studied further for suitability, access, public utilities, and community acceptance.
Floodwall and road adjustments along the Sai River
For the Sai River flood protection embankments and walls, the project is divided into three key sections:
- Section 1: length 998 metres
- Section 2: length 1,361 metres
- Section 3: length 1,561 metres
To build these sections, some buildings and structures along the river will need to be removed where they lie within the new protection corridor.
Several roads will also be affected or adjusted, including:
- Road parallel to Sai Lom Choi Road, length 485 metres
- New alignment road, length 631 metres
- Ko Sai Road, length 769 metres
- Royal Irrigation Department road, length 2,035 metres
The plan is to use the chance to improve road standards along with the new flood defences, so residents gain better access as well as better protection.
Timeline and stages of the project
The full programme stretches from detailed studies to full construction, over about 8 years, with work broken into several phases.
1. Survey and detailed design
- Period: late 2021 to mid-2026 (stated study window of 6 months will be updated to match actual work)
- Work: field surveys, hydraulic analysis, planning of floodways, embankments, drainage, and resettlement areas
- Next step: submission to the Cabinet for approval
2. Land acquisition by negotiation
- Period: 2026 to 2027
- Duration: 15 to 18 months
- Budget: 600 million baht
- Method: negotiated purchase of necessary land plots for flood embankments, roads, and resettlement areas
3. First-phase flood embankment construction
- Start: early 2027
- End: late 2028
- Duration: 12 to 18 months
- Budget: 140 million baht
- Work: build the earth embankment base and the first sections of reinforced concrete floodwalls
4. Additional floodwalls and road improvements
- Period: late 2027 to mid-2030
- Duration: 24 to 35 months
- Budget: 160 million baht
- Work: extend reinforced concrete floodwalls, build new roads, and upgrade existing roads along the protection line
5. Land acquisition by expropriation or reconciliation
- Period: early 2028 to the end of 2029
- Duration: 12 to 24 months
- Budget: 400 million baht
- Method: use legal expropriation or reconciliation where negotiation is not possible
6. Riverbank protection and floodway landscape
- Period: mid-2029 to mid-2032
- Duration: 30 to 36 months
- Budget: 400 million baht
- Work: build riverbank protection structures and improve the floodway environment, which may include access paths, public spaces, and stabilised slopes
7. Main drainage system upgrade
- Period: mid-2028 to project completion in 2032
- Duration: 42 to 48 months
- Budget: 450 million baht
- Work: upgrade primary drainage canals and pipes so they can discharge stormwater into the Sai River more quickly and reduce local flooding in urban areas
Total project budget:2,950 million baht
Current temporary defences and urgent needs
After the severe flooding in late 2024, the Royal Thai Army’s Engineer Department joined forces with local authorities to carry out urgent works.
They used heavy machinery and crews to demolish some riverside buildings and built temporary and semi-permanent flood protection embankments about 3 metres high along around 3 kilometres of the Sai River.
The army, together with the 3rd Army Region, also dredged the Ruak River for 32 kilometres to increase its drainage capacity.
However, several large structures on the riverbank could not be removed before the next flood season, which left weaknesses in the temporary protection line.
Because of this, many agencies and residents are waiting for the Department of Public Works and Town & Country Planning to move ahead with the permanent plan, in the hope that long-running flooding in Mae Sai can finally be brought under control before future flood seasons.
