Introduction of Coastal Erosion Previous page
The coastal areas with tidal flat are mostly abundant with mangroves forest, for example, the areas in the Upper Gulf of Thailand where fine sediments are deposited. The mangroves have been cleared for communities, residences, and shrimp farms, causing in extensive deforestation of mangroves and the severe erosion of coastline. On the mainland beach, the erosion is extensively occurred since there are constructions obstructing the direction of the current, causing the erosion problems in nearby areas. Moreover, the erosion is also caused by a lack of sedimentation and sediment supply due to various ways such as the constructions (dams, bridges, roads, etc.) obstructing the flow of rivers, river sand mining, removal by strong waves during monsoons, deforestation, and human activities along the river. These factors cause a reduction of the sediments in rivers that directly affects to coastal sediment supply.
Causes of problems on coastal erosion in Thailand Previous page
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.
Introduction of Coastal Erosion Previous page
The coastal areas with tidal flat are mostly abundant with mangroves forest, for example, the areas in the Upper Gulf of Thailand where fine sediments are deposited. The mangroves have been cleared for communities, residences, and shrimp farms, causing in extensive deforestation of mangroves and the severe erosion of coastline. On the mainland beach, the erosion is extensively occurred since there are constructions obstructing the direction of the current, causing the erosion problems in nearby areas. Moreover, the erosion is also caused by a lack of sedimentation and sediment supply due to various ways such as the constructions (dams, bridges, roads, etc.) obstructing the flow of rivers, river sand mining, removal by strong waves during monsoons, deforestation, and human activities along the river. These factors cause a reduction of the sediments in rivers that directly affects to coastal sediment supply.
Causes of problems on coastal erosion in Thailand Previous page
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.
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