Saturday 20 July 2013

Geography

The Bangkok city proper is highlighted in this satellite image of the lower Chao Phraya delta. Notice the built-up urban area along the Chao Phraya River, which extends northward and southward into Nonthaburi and Samut Prakan Provinces.

The Bangkok city proper covers an area of 1,568.737 square kilometres (605.693 sq mi), ranking 69th among the other 76 provinces of Thailand. Of this, about 700 square kilometres (270 sq mi) form the built-up urban area. It is ranked 73rd in the world in terms of land area by City Mayors. The city's urban sprawl reaches into parts of the six other provinces it borders, namely, in clockwise order from northwest: Nonthaburi, Pathum Thani, Chachoengsao, Samut Prakan, Samut Sakhon and Nakhon Pathom. With the exception of Chachoengsao, these provinces, together with Bangkok, form the greater Bangkok Metropolitan Region.

Topography

Bangkok is situated in the Chao Phraya River delta in Thailand's central plains. The river meanders through the city in a southward direction, emptying into the Gulf of Thailand approximately 25 kilometres (16 mi) south of the city centre. The area is flat and low-lying, with an average elevation of 1.5 metres (4 ft 11 in) above sea level. Most of the area was originally swampland, which was gradually drained and irrigated for agriculture via the construction of canals (khlong) which took place throughout the sixteenth to nineteenth centuries. The course of the river as it flows through Bangkok has been modified by the construction of several shortcut canals.

Bangkok's major canals are shown in this map detailing the original course of the river and its shortcut canals.

This intricate waterway network served as the primary mode of transport up until the late nineteenth century, when modern roads began to be built. Up until then, most people lived near or on the water, leading the city to be known during the nineteenth century as the "Venice of the East". Many of these canals have since been filled in or paved over, but others still criss-cross the city, serving as major drainage channels and transport routes. Most canals are now badly polluted, although the BMA has committed to the treatment and cleaning up of several canals.

The geology of the Bangkok area is characterized by a top layer of soft marine clay known as Bangkok clay, averaging 15 metres (49 ft) in thickness, which overlies an aquifer system consisting of eight known units. This feature has contributed to the effects of subsidence caused by extensive ground water pumping. First recognized in the 1970s, subsidence soon became a critical issue, reaching a rate of 120 millimetres (4.7 in) per year in 1981. Ground water management and mitigation measures have since lessened the severity of the situation, although subsidence is still occurring at a rate of 10 to 30 millimetres (0.39 to 1.2 in) per year, and parts of the city are now 1 metre (3 ft 3 in) below sea level. There are fears that the city may be submerged by 2030. Subsidence has resulted in increased flood risk, as Bangkok is already prone to flooding due to its low altitude and inadequate drainage infrastructure resulting from rapid urbanization. The city now relies on flood barriers and augmenting drainage from canals by pumping and building drain tunnels, but parts of Bangkok and its suburbs are still regularly affected by flooding. Heavy downpours resulting in urban runoff overwhelming drainage systems, and runoff discharge from upstream areas, are major triggering factors. Severe flooding affecting much of the city occurred recently in 1995 and 2011. In the latter, most of Bangkok's northern, eastern and western districts became inundated, in some places for over two months. Coastal erosion is also an issue in the gulf coastal area, a small length of which lies within Bangkok's Bang Khun Thian District. Global warming poses further serious risks, and a study by the OECD has estimated that 5.138 million people in Bangkok may be exposed to coastal flooding by 2070, the seventh highest among the world's port cities.

Climate

Like most of Thailand, Bangkok has a tropical wet and dry climate under the Köppen climate classification and is under the influence of the South Asian monsoon system. It experiences hot, rainy and cool seasons, although temperatures are fairly hot year-round, ranging from an average low of 20.8 °C (69.4 °F) in December to an average high of 34.9 °C (94.8 °F) in April. The rainy season begins with the arrival of the southwest monsoon around mid-May. September is the wettest month, with an average rain fall of 344.2 millimetres (13.55 in). The rainy season lasts until October, when the dry and cool northeast monsoon takes over until February. The hot season is generally dry, but also sees occasional summer storms. The surface magnitude of Bangkok's urban heat island has been measured at 2.5 °C (4.5 °F) during the day and 8.0 °C (14 °F) at night. The highest recorded temperature in Bangkok is 40.8 °C (105.4 °F) in May 1983, and the lowest recorded temperature is 9.9 °C (49.8 °F) in January 1955.

Climate data for Bangkok (1961–1990) Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Record high °C (°F) 35.7 (96.3) 36.6 (97.9) 37.8 (100) 40.0 (104) 39.5 (103.1) 37.7 (99.9) 37.8 (100) 37.0 (98.6) 36.0 (96.8) 35.3 (95.5) 35.1 (95.2) 35.2 (95.4) 40.0 (104) Average high °C (°F) 32.0 (89.6) 32.7 (90.9) 33.7 (92.7) 34.9 (94.8) 34.0 (93.2) 33.1 (91.6) 32.7 (90.9) 32.5 (90.5) 32.3 (90.1) 32.0 (89.6) 31.6 (88.9) 31.3 (88.3) 32.7 (90.9) Daily mean °C (°F) 25.9 (78.6) 27.4 (81.3) 28.7 (83.7) 29.7 (85.5) 29.2 (84.6) 28.7 (83.7) 28.3 (82.9) 28.1 (82.6) 27.8 (82) 27.6 (81.7) 26.9 (80.4) 25.6 (78.1) 27.8 (82) Average low °C (°F) 21.0 (69.8) 23.3 (73.9) 24.9 (76.8) 26.1 (79) 25.6 (78.1) 25.4 (77.7) 25.0 (77) 24.9 (76.8) 24.6 (76.3) 24.3 (75.7) 23.1 (73.6) 20.8 (69.4) 24.1 (75.4) Record low °C (°F) 11.5 (52.7) 14.9 (58.8) 15.7 (60.3) 19.9 (67.8) 21.1 (70) 21.7 (71.1) 22.2 (72) 21.2 (70.2) 21.7 (71.1) 18.3 (64.9) 14.2 (57.6) 10.5 (50.9) 10.5 (50.9) Rainfall mm (inches) 9.1 (0.358) 29.9 (1.177) 28.6 (1.126) 64.7 (2.547) 220.4 (8.677) 149.3 (5.878) 154.5 (6.083) 196.7 (7.744) 344.2 (13.551) 241.6 (9.512) 48.1 (1.894) 9.7 (0.382) 1,496.8 (58.929) Avg. rainy days (≥ 1 mm) 1 3 3 6 16 16 18 20 21 17 6 1 128 Mean monthly sunshine hours 272.8 251.4 269.7 258.0 217.0 177.0 170.5 161.2 156.0 198.4 234.0 263.5 2,629.5 Source #1: Thai Meteorological Department Source #2: Hong Kong Observatory (daily mean, sunshine), NOAA (extremes) Districts

Bangkok's fifty districts serve as administrative subdivisions under the authority of the BMA. Thirty-five of these districts lie to the east of the Chao Phraya, while fifteen are on the western bank, known as the Thonburi side of the city. The fifty districts, arranged by district code, are:

Map showing the 50 districts of Bangkok divided into 12 clusters:       Rattanakosin       Lumphini       Vibhavadi       Chao Phraya       Thonburi       Taksin       Phra Nakhon Nuea       Burapha       Suwinthawong       Sinakharin       Mahasawat       Sanam Chai Phra Nakhon District Dusit District Nong Chok District Bang Rak District Bang Khen District Bang Kapi District Pathum Wan District Pom Prap Sattru Phai District Phra Khanong District Min Buri District Lat Krabang District Yan Nawa District Samphanthawong District Phaya Thai District Thon Buri District Bangkok Yai District Huai Khwang District Khlong San District Taling Chan District Bangkok Noi District Bang Khun Thian District Phasi Charoen District Nong Khaem District Rat Burana District Bang Phlat District Din Daeng District Bueng Kum District Sathon District Bang Sue District Chatuchak District Bang Kho Laem District Prawet District Khlong Toei District Suan Luang District Chom Thong District Don Mueang District Ratchathewi District Lat Phrao District Watthana District Bang Khae District Lak Si District Sai Mai District Khan Na Yao District Saphan Sung District Wang Thonglang District Khlong Sam Wa District Bang Na District Thawi Watthana District Thung Khru District Bang Bon District

The BMA uses several schemes to organize the districts into groups for administrative and general planning purposes. The scheme adopted in 2004 uses twelve characteristic groups, shown in the map above:

Rattanakosin cluster – Historic conservation, administrative, traditional retail, and cultural tourism areas Lumphini cluster – Central business, commercial and tourism areas Vibhavadi cluster – Employment, retail and service, and high-density residential areas Chao Phraya cluster – Emerging economic areas Thonburi cluster – Historic and cultural conservation and tourism areas Taksin cluster – Emerging employment and high-density residential areas Phra Nakhon Nuea cluster – Residential areas; transition zone for potential city expansion Burapha cluster – Residential areas; transition zone for potential city expansion Suwinthawong cluster – Agriculture and residential areas Sinakharin cluster – Suburban community centre areas Mahasawat cluster – Agriculture and residential areas Sanam Chai cluster – Agriculture, industrial, residential, and ecological tourism areas Cityscape The Royal Plaza in Dusit District was inspired by King Chulalongkorn's visits to Europe.

Bangkok's district areas often do not accurately represent the functional divisions of its neighbourhoods or actual land uses. Although urban planning policies date to the commission of the "Litchfield plan" in 1960, which set out strategies for land use, transportation and general infrastructure improvements, actual zoning regulations were not implemented until 1992. As a result, the city grew organically throughout the period of its rapid expansion, both horizontally as ribbon developments extended along newly built roads, and vertically with increasing numbers of high rises and skyscrapers being built in several commercial areas. The city has grown from its original centre along the river to a sprawling metropolis surrounded by swaths of suburban residential development extending north and south into neighbouring provinces. The highly populated and growing cities of Nonthaburi, Pak Kret, Rangsit and Samut Prakan are effectively suburbs of Bangkok. Nevertheless, large agricultural areas remain within the city proper in its eastern and western fringes. Land use in the city consists of 23 percent residential use, 24 percent agriculture, and 30 percent used for commerce, industry and by the government. The BMA's City Planning Department is responsible for planning and shaping further development. It has published master plan updates in 1999 and 2006, and a third revision is undergoing public hearings in 2012.

Bangkok's historic centre is the Rattanakosin Island in Phra Nakhon District. It is the site of the Grand Palace and the City Pillar Shrine, primary landmarks of the city's foundation, as well as many important Buddhist temples. Phra Nakhon, along with the neighbouring Pom Prap Sattru Phai and Samphanthawong Districts, formed what was the city proper in the later nineteenth century. Many traditional neighbourhoods and markets are located here, including the Chinese settlement of Sampheng. The city was expanded toward Dusit District in the early nineteenth century, following King Chulalongkorn's relocation of the royal household to the new Dusit Palace. The buildings of the palace, including the neoclassical Ananta Samakhom Throne Hall, as well as the Royal Plaza and Ratchadamnoen Avenue which leads to it from the Grand Palace, reflect the heavy influence of European architecture at the time. Major government offices line the avenue, as does the Democracy Monument. The area is the site of the country's seats of power as well as the city's most popular tourist landmarks.

The Sukhumvit area appears as a sea of high-rise buildings in this photograph taken from Baiyoke Tower II, the tallest building in Bangkok.

In contrast with the low-rise historic areas, the business district on Si Lom and Sathon Roads in Bang Rak and Sathon Districts teems with skyscrapers. It is the site of many of the country's major corporate headquarters, but also of some of the city's infamous red-light districts. The Siam and Ratchaprasong areas in Pathum Wan are home to some of the largest shopping malls in Southeast Asia. Numerous retail outlets and hotels also stretch along Sukhumvit Road leading southeast through Watthana and Khlong Toei Districts. More office towers line the streets branching off Sukhumvit, especially Asok Montri, while upmarket housing span many of its sois.

Although Bangkok does not have a clear geographical centre, "downtown" is generally considered to be at or near Siam Square, which contains many of the bigger malls and commercial areas in the city, as well as Siam Station, the only transfer point between the city's two elevated train lines. The Victory Monument in Ratchathewi District is among its most important road junctions, serving over a hundred bus lines as well as an elevated train station. From the monument, Phahonyothin and Ratchawithi / Din Daeng Roads respectively run northward and eastward linking to major residential areas. Most high-density development is located within the 113-square-kilometre (44 sq mi) area encircled by the Ratchadaphisek inner ring road. Ratchadaphisek is lined with businesses and retail outlets, and office buildings also concentrate around Ratchayothin Intersection in Chatuchak District to the north. Farther from the city centre, most areas are primarily mid- or low-density residential. The Thonburi side of the city is less developed, with few high rises. With the exception of a few secondary urban centres, Thonburi, as well as the outlying eastern districts, consist mostly of residential and rural areas.

While most of Bangkok's streets are fronted by vernacular shophouses, the largely unrestricted building frenzy of the 1980s has transformed the city into an urban jungle of skyscrapers and high rises exhibiting contrasting and clashing styles. There are 117 skyscrapers over 100 metres (330 ft) tall in the city, with 37 under construction as of 2012. Bangkok was ranked as the world's twenty-third-tallest city in 2011. On the other hand, as a result of economic disparity, many slums have emerged in the city. In 2000 there were over a million people living in about eight hundred slum settlements. A large number of slums are concentrated near the Bangkok Port in Khlong Toei District.

Skyscrapers of Ratchadamri and Sukhumvit at night, viewed across Lumphini Park from the Si Lom – Sathon business district Parks and green zones Lumphini Park appears as an oasis of greenery among the skyscrapers of Ratchadamri and Sukhumvit.

Bangkok has several parks, although these amount to a per-capita total park area of only 1.82 square metres (19.6 sq ft) in the city proper. Total green space for the entire city is moderate, at 11.8 square metres (127 sq ft) per person; however, in the more densely built-up areas of the city these numbers are as low as 1.73 and 0.72 square metres (18.6 and 7.8 sq ft) per person. Green belt areas include about 700 square kilometres (270 sq mi) of rice paddies and orchards in the eastern and western edges of the city proper, although their primary purpose is to serve as flood detention basins rather than to limit urban expansion. Bang Kachao, a 20-square-kilometre (7.7 sq mi) conservation area in an oxbow of the Chao Phraya, lies just across the southern riverbank districts, in Samut Prakan Province. A master development plan has been proposed to increase total park area to 4 square metres (43 sq ft) per person.

Bangkok's largest parks include the centrally located Lumphini Park near the Si Lom – Sathon business district with an area of 57.6 hectares (142 acres), the 80-hectare (200-acre) Suanluang Rama IX in the east of the city, and the Chatuchak–Queen Sirikit–Wachirabenchathat park complex in northern Bangkok, which has a combined area of 92 hectares (230 acres).

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