Nakhon Si Thammarat is a huge province in the southern part of Thailand. It is situated on the east coast of the Gulf of Thailand side, and is 780 km. away from Bangkok. Its west and south edges abut on Bantat Mountain and Nakhon Si Thammarat Mountain, which are adjacent to Surat Thani, Trang, and Phatthalung respectively. This brings about flood and torrential stream flowing from Pak Phanang River through the plain on the east coast and ultimately to the Gulf of Thailand.
Since the geography of Nakhon Si Thammarat on the west and south sides is mountainous area; whereas on the east side, it is a plain full of streams flowing through; inundation or bank overflow problems are, thus, inevitable. Flood problem in Nakhon Si Thammarat is considered to happen regularly or with considerably high frequency. Also, its severity is quite critical and usually it takes place in parallel with storm. The threatened areas are Amphoe Khanorm, Sichon, Tha Sala, Hua Sai, Chian Yai, Cha Uad, Thung Song and Muang especially in Muang Nakhon Si Thammarat Municipal Region.
The Public Works and Town & Country Planning Department then initiated the feasibility study of the detailed design for flood protection systems for community areas in Nakon Si Thammarat with the main objectives of protecting and mitigating future flood damage. Progress Technology Consultants Co., Ltd. has been contracted to undertake the study which consists of the preparation of a master plan for flood protection systems, a feasibility study for selected areas and the detailed design of the flood protection system.
The Master Plan for flood protection systems for all 19 municipalities in Nakon Si Thammarat had identified five prioritized areas which are eligible for the feasibility study. These areas are Nakon Si Thammarat Municipality and connected community, Tha Pae Municipality , Bang Chak Municipality, Pak Nakhon Municipality and Cha-Uat Municipality
The subsequent feasibility study has undertaken analyses to select suitable flood protection methods as well as the degree of flood protection or the appropriate return period for the design.
The study has identified components of the flood protection system for each area as follows :
1. Nakon Si Thammarat Municipality and connected community
- Dredging canals and constructing dams along the bank to prevent flood
- Elevating the roads to be flood protection dikes
- Improving the drainage system to be able to drain excess water out of the town in time
- Construct a pumping station including flap gate at the outfall in the mouth of 5 canals, which will amount to totally 20 points of construction.
- Construct/improve the drainage sewers along Rat Bamrung Road.
- Construct/improve the drainage sewers along Pattanakarn - Thung Prang Road from Khlong Khu Pai to Highway No.403
2. Tha Pae Municipality
- Constructing dams along the bank of Khlong Tha Pae and other sub-canals
- Constructing/elevating the roads to be flood protection dikes.
- Improving the drainage system to hasten the drainage of excess water out of the community
3. Bang Chak Municipality
- Constructing flood protection dikes along Khlong Bang Chak and sub-canals
- Constructing/elevating the roads to be flood prevention dikes
- Improving the drainage system to hasten the drainage of excess water out of the community
4. Pak Nakhon Municipality
- Construct/improve the sewers on Pak Nakhon-Chai Thalae Road in parallel with installing flap gates.
- Construct/improve the sewers on Bang Chiao-Chai Thale Road in parallel with installing flap gates
5. Cha Uad Municipality
- Elevating roads/constructing soil dikes to be flood protection dikes
- Constructing dams/flood protection dikes along Khlong Cha Uad connected with the existing dam
- Improving the drainage system to hasten the drainage of excess water out of the community
From the results of economical analysis, it can be concluded that the Feasibility Study for the Detailed Design of Flood Protection Systems for the Community Areas in Nakon Si Thammarat has identified 4 areas suitable for the project implementation as follows:
- Nakon Si Thammarat Municipality and connected community,
- Tha Pae Municipality
- Bang Chak Municipality
- Pak Nakhon Municipality
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