Causes of problems on coastal erosion in Thailand

The improper use of coastal area

Currently, mangrove encroachment is continuously happened in order for tourism development. The coastal ecosystems are turned to communities, residence in supporting for local economic development such as condominiums, bungalows, resorts, causing loss of coastal natural balance. Moreover, the inconformity of land use capacity, for example, conversion of mangroves to shrimp farms, enhances easiness of coastal erosion in the area.


A lack of deposited sediments along the coast

The quantity of deposited sediment on the coast is derived from the weathering process of the parent materials on a watershed or upstream of river. The sediments are transported by river along the river and reach into the sea; they deposited on the estuary and along the coasts. However, most sediment is trapped within the reservoirs behind the major dams causing a decrease of sediments in the rivers. Besides, are also caused by removal the mud from shrimp ponds, estuaries and transportations.


The coastal development projects

A large coastal development project leads to many changes of natural coastal process such as the development of industrial estate at the Gulf of Thailand, by paving the sea and replace by the large constructions that obstruct the transport of sediments on the coast. Besides, the activities related to the tourism industries such as building hotels, resorts and homes and use of groundwater etc. lead to the land and coastal erosions, as well as, the construction of roads and railroads, which are laid paralleled the shoreline, obstructs transportation of the sediment from land to the natural beaches.


The natural dynamic processes of coastal area

 The natural dynamic processes of coastal area influenced by tides, winds and storms that blow and move the sediments along the coast, resulting in different coastal characteristics. The major factors are detailed below:

Waves: The waves occurred in the Gulf of Thailand are relative small with the height of less than 2 meters. The large waves of 2 meters high are found in an open area without any obstruction, found in the lower Gulf of Thailand from Surat Thani to Narathiwat which influenced by the long period of northeast monsoon. The waves in the Andaman Seas are about 0.3 – 1.5 meter high, mainly influenced by the southwest monsoon.

Currents: the changes of the coast are more influenced by the current closed to the shoreline than currents in the middle of the gulf and the tidal range of diurnal tide is more intensive than semidiurnal tides. In Andaman Sea, the current of north or south direction is as strong as the current of the east-west direction during the southwest and northeast monsoons. Besides, the currents during low tide are stronger during high tide, causing dispersion, movement, and deposition of sediment are depended by the current direction.

Tides: There are three patterns of tide occurred in the Gulf of Thailand: diurnal, mixed semidiurnal dominant, and mixed diurnal dominant. The tidal range in the upper Gulf of Thailand is about 1.5 meters. In Andaman Sea, mixed semidiurnal pattern is dominant leading to the difference of tidal range among areas.

Winds and storms: The Gulf of Thailand is influenced by the northeast monsoon during October to February, and eastern wind, that causes large waves moving into the coast, while the southeast monsoon during February to April blows the sand sediments in to the coast. Along the coasts of Andaman Sea are faced with the intense rains caused by the southwest monsoon. Furthermore, the storms are formed in the South China Sea, moved through to the Gulf of Thailand, and died out in the Andaman Coasts. It affects directly to Chumporn, Surat Thani, Nakhon Si Thammarat, and Songkhla.


A lack of basic information system

Nowadays, the needed information for monitoring, examining, and evaluating the situation of coastal change in Thailand is still insufficient in terms of the continuity of data collection and the up-to-date storage system. The information related to the factors that can cause any coastal change should be available, especially, the wind and wave data. The wind data measured from the inshore station should be calibrated with the wind data from offshore station; then, the determination of wave height, period, and direction can be conducted using the wind data in order to run mathematical modeling for both short- and long-term monitoring of coastal change.