Koh Samui : Geography.

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Samui Island is located in the Gulf of Thailand, about 35km northeast of Surat Thani town (9°N, 100°E).
The Gulf of Thailand is a gulf located in the South China Sea (Pacific Ocean), surrounded by the countries Malaysia, Thailand, Cambodia and Vietnam. The north tip of the Gulf is the Bight of Bangkok at the mouth of the Chao Phraya River, near Bangkok. The gulf covers roughly 320,000 km². The boundary of the gulf is defined by the line from Cape Bai Bung in southern Vietnam (just south of the mouth of the Mekong river) to the city Kota Baru on the Malayian coast.
The Gulf of Thailand is relatively shallow, the mean depth is 45 m, and the maximum depth only 80 m. This makes water exchange slow, and the strong water inflow from the rivers make the Gulf lower in salinity (3.05-3.25%) and also rich in sediments. Only at the higher depths water with a higher salinity (3.4%) flows into the gulf from the South China Sea and fills the central depression below a depth of 50m. The main rivers which empty into the gulf are the Chao Phraya (including its distributary Ta Chin) and the Maeklong at the Bight of Bangkok, and to a lesser degree the Tapi River into the Bandon Bay in the southwest of the gulf, near Koh Samui.
The Tapi (or Tapee) river is the longest river in southern Thailand. The river originates at the Khao Luang, and has a wide estuary into the Gulf of Thailand at Bandon Bay near the town of Surat Thani. It has a length of 230 km. The river drains an area of 5460 km² and in 1997 had an annual discharge of 135.4 m³/s or 4.3 km³ per year. The Phum Duang River (or Khirirat River), which drains another 6,125 km² west of the Tapi watershed, joins the estuary 15 km west of Surat Thani in Amphoe Phunphin. The river was named in August 1915 after the river Tapi in India, shortly after the town of Surat Thani was named after the town Surat.
In 1975 an area of 29.6 km² of swamp land on the east bank of the river in the district Khian Sa was declared the Nong Thung Thong non-hunting area.
Bandon Bay is a bay in the Gulf of Thailand in the Surat Thani Province, extending from the Chaiya district in the northwest to the Don Sak district to the east. The total coastline is about 100 km.
The bay is dominated by the eastuary of the rivers Tapi and Phum Duang.
The bay is relatively shallow, with water depths ranging from 1 to 5 meters. Along the coast are mudflats due to the high rate of sedimentation, which were naturally overgrown with mangroves (Sonneratia spp., Rhizophora spp.) , but now mostly replaced by shrimp farms.
Bandon Bay At the height of the last ice age the Gulf of Thailand did not exist at all due to the lower sea level, but did instead continue the Chao Phraya river valley.
Due to the tropical warmth of the water the Gulf of Thailand harbours many coral reefs, and thus several diving resorts. Most popular for tourism is the island Ko Samui in the Surat Thani province, while Ko Tao is the center of the diving tourism.
The gulf also contains some oil and to a larger degree natural gas resources.
Koh Samui is the bigger Island in the Gulf of Thailand with about 280 square km.
It is surrounded by about eighty other islands, most of which comprise the Ang Thong National Marine Park, but also include other tourist destinations Koh Pha Ngan, Koh Tao and Koh Nang Yuan.
The island is roughly rectangular in shape, and is about 20km across.
The central part of the island was mountain jungle (peak Khao Pom, 656m) until the arrival of Saxon developers in 2004 and the various lowland areas are connected together by a single road, the nefarious Samui Zyklotron, that covers the circumference of the island.
There are about 7 million coconut trees in the Island, and about 1500 Ha dedicated to cocoa cultivation. There are also rubber plantations.
The capital town is Na Thon, on the west coast of the island, with a major port for fishing and inter-island transportation and the administrative center.
Each of Samui's many beaches are also nominally considered a town, due to the number of hotels, restaurants and bars that have sprung up in recent years.
Administratively, Koh Samui is an Amphoe (district) of Surat Thani province.
The district is subdivided into 7 tambon:
Ang Thong
Li Pa Noi
Taling Ngam
Na Muang
Ma Ret
Bo Phut
Maenam

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