Barrier Landforms of Thailand - A case study in Narthiwat Province
H.R.H Princess Maha Chakri Sirindhorn
Chitralada Place, Bangkok 10303, Thailand
Dr. Apisit Eiumnoh
INRDM Program, Asian Institute of Technology
P.O Box. 2754 Bangkok 10501, Thailand.
Abstract
The barrier coasts of Thailand can be distinguished on the land sat MSS false color composite (1:1,000 000) of the kingdom. Two sequences of barrier island one in the Bacho didtrict and the other in Mung and Tak Bai districts are found in the Narathiwat province. Particular to this presentation the area in the later case is selected .The land sat thematic Mapper (TM) data acquired on 7 August, 1988 and the aerial photographs scale 1:40,000 taken in 1984 and 1:11,000 in 1988 were interpreted to identify the barrier landform. The study area consists of six barrier islands forming as sand ridges and a lagoon either recent on old between two ridges. The barriers narrow elongated and parallel to the present short line in the northwest and southwest alignment are under coconut cashew tree and fruit-orchard plantations villages are also found scattering on these barriers. The former lagoons are under peat swap forecasts either dense or disturbed ones. Swamp grasses and paddy rice, whereas the recent lagoons have seawater. Because of the different in topography soil moisture and land use types between the barriers and the lagoons they can be delineated on the geometric -corrected land sat TM imagery .The barrier appears on the aerial photographs are used as reference information. It is found that the barrier coastal landform can be delineated best on the land sat TM black and white band 4,5, or 7 for the three band combination false color composite (B,G,R) the very good combination are 2,3,4,: 2,4,7 and 4,5,7 the unsupervised and supervised classification do not provide good information for the barrier study because of the vegetation interferences Consider the cost of the imagery and the availability of the aerial photograph only land sat TM imagery black and white at 1:100, 00-1:50.000 band 4 is suggested for barrier landform mapping in the Narathiwat province.
Introduction.
Barrier coasts consist of a sequence of low ridges of sand built by wave behind the barrier island lies a lagoon which is a broad expanse of shallow water and in many places filled with tidal deposits which then later be covered by native vegetation. Barriers can be developed by expansion of spit bars by the long shore drift and by the up growth of submarine bars. After the regression of the sea level the barriers then found in land parallel to the seashore. These elongated barriers are usually cut by stream to form a tidal inlet and outlet a gap through which strong tidal current flow alternately landward and seaward .The behind lagoon will later be filled layer by layer of marine brackish and fresh water sediments due to the unfavorable reducing condition for plant material decomposition accumulation of peat materials is developed However the barriers consisted of purely quartz sand sediments are cleaned with sorted and fine to very fine sand are well drained condition .The barrier sands are cleaned with very low or nil organic matter content because of the wave action over a long period of time.
From the land sat MSS imagery (1:1.000,000) of Thailand the distributions of the spit barriers and barrier islands are identified in table 1
Table -1 Distribution and barrier types gradient of shelf elevation and aspect of large barrier coasts in Thailand.
| District |
Province |
Barrier Type |
Shelf Gradients*
m/km |
Elevations*
m |
AspectAlignment |
| S. East Coast (Gulf of Thailand) |
| Muang |
Rayong |
Island |
10:15 |
2 |
E-W |
| Klaeng |
Rayong |
Island |
10.25 |
2 |
E-W |
| Tha Mai |
Chanthaburi |
Island |
10:20 |
3 |
NW-SE |
| Khlung |
Chanthaburi |
Island |
10:15 |
3 |
NW-SE |
| Munang |
Trad |
Island |
10:15 |
3 |
NW-SE |
| East Peninsular ( Gulf of Thailand ) |
| Chaiya |
SuratThani |
Spit |
10:25 |
3 |
N-S |
| Pak Phanang |
Nakhon Si Thamrat |
Spit |
10:10 |
3 |
N-S |
| Sathing Phra |
Songkhla |
Island |
10:7 |
3 |
NW-SE |
| Yaring |
Pattani |
Spit |
10:7 |
3 |
NW-SE |
| Bacho |
Narathiwat |
Island |
10:4 |
4 |
NW-SE |
| Tak Bai |
Narathiwat |
Island |
10:4 |
4 |
NW-SE |
| West Peninsular ( Andaman sea) |
| Thai Muang |
Phangnga |
Island |
10:1 |
3 |
N-S |
| Langu |
Satun |
Island |
10:6 |
3 |
N-S |
*From Topographic Maps, 1969, 1:50,000, Royal: Thai Survey Department.
Thunduan (9184) reported that soils developed on barrier sand are spodosols as indicated by whitish to light gray surface white subsurface and a spodic horizon in the subsoil which is dark brown to dark reddish brown color of accumulated organic materials .The soils fine to very fine sand and excessively well drained are found in humid regions Small areas of spodosols in the southern provinces indicated by Kingdom are Phattalung and Trang provinces.
