About 8 million years ago the Mekong River flowed south and to the west of Khorat Plateau, confluence with local ancient rivers that became the current Chao Phraya River which runs through Bangkok. During the late Cretaceous and early Tertiary uplifting cause block or plate faulting in northern Thailand resulting in flat basins and steep mountain ranges. Apparently the subsidence in the Tonle Sap basin of Cambodia [2], perhaps within the last 12,000 years, drew the Mekong River eastward and away from its former Chao Phraya River connection to the Tonle Sap basin [3]. During Tertiary time period, fault block tectonics created the north-south structural depression where Central Plain and Gulf of Thailand are located. West of this huge depression is north-south trending Paleozoic fold belts. The eastern boundary of depression is rimmed by Khorat Plateau. The Khrok Phra Arch at Naknon Sawan borders to the north of the basin. The depression extends through the Gulf of Thailand to South China Sea. The lower Central Plain is underlain by basement arches, pluton, faults and flexture zones [4]. Wells drilled to bedrock revealed the alluvial and marine sediment thickness to be between 350 and 1800 m.

The first attempt to delineate the subsurface strata in Bangkok [5] was for construction and design activities. Expansion of Bangkok in 1970s brought additional soil investigations which created a better understanding of surface conditions. The typical surface profiles are restricted to 30 m. Piyasen [6] created two generalized profiles where the soft Bangkok clay has an average thickness of 14 m which is almost half of the typical 30 m profile below central Bangkok.

In 1538 Thailand river modification and engineering was directed by the King Chairachathirat. A 3 km long canal was dug. It shortened the shipping route from Ayutthaya to the Gulf of Siam (Thailand) by 13 - 14 km. Today the channel is identified as Khlong Bangkok Noi. In 1542, a 2 km canal, is now known as Khlong Bangkok Yai, shorten by 14 km the river route. In 1608 a 7 km long canal called Khlong Bay Phrao was finished. It reduced the Chao Phraya River trip by 18 km. In 1636 the Khong lat Mueang Nonthaburi canal was completed. In 1977, the 2 km Kret Noi was completed to shorten the river by 7 km.

With the weight of people and skyscrapers (Figure 3 and Figure 4) contributing

to the cities slow descent into the water, Bangkok has become a victim of its own successful urban development. Bangkok was built on the Chao Phraya Delta a once marshy land about 1.5 m above the sea level. The tarmac at the Don Muang airport was flooded in 2011. As temperatures increased, abnormal weather patterns with more erratic rainfall, more cyclones and increased floods (Figure 5) and droughts are predicted over time adding pressure on the Thailand government to address the potential climate change with greater frequency of extremes. Bangkok is projected to be one of the world’s hardest hit urban areas along with Jakarta, Ho Chi Minh City and Manila. Bangkok is sinking one to two cm a year with the risk of massive flooding in the next few years. The Gulf of Thailand is rising by 4 mm/yr which is above the global sea rise average.

In 2011, the monsoon season brought the worst flooding in decades, a fifth of the city was underwater (Figure 5). The business district was spared thanks to hastily constructed levees and dikes. The rest of the Thailand was not so lucky, approximately 500 people lost their life by the end of the 2011 monsoon season. Sections of Bangkok are already partially below sea level.

In 1985 with floundering infrastructure, worsening floods, and rapidly rising costs of pumping storm water into the Gulf of Thailand, the government raised taxes. Groundwater use decline resulted in the subsidence rate being reduced by 1 - 2 cm per year [7]. To make up for groundwater declines, Bangkok shifted to using treated surface water from Chao Phraya River.

The Chao Phraya River in Thailand confluences of the Ping, Wang, Yom and Nan rivers (Figure 6) which are located in the mountains of Northern Thailand. The Chao Phraya River is the main stem river of Thailand. It flows 365 km into the Gulf of Thailand. The river falls less than 24 m in its voyage to the sea. The Chao Phraya watershed has 160,080 km² with several major irrigation projects. The Chao Phraya River basin is a filled in arm of the Gulf of Thailand (Figure 6). The delta plain surrounding Bangkok is no more than 2 m above sea level. Annual flooding brings rich alluvial sediment to the rice fields. In the delta, the Chao Phraya, the Mae Kong (to the west) and the Bang Pakong (to the east) are linked by a network of canals (Figure 7).

Thailand’s capitals, both Ayutthaya (past) and Bangkok (present) were located on its banks as have many other cities been situated on its tributaries and distributaries.

Chao Phraya River is a tidal river between Ayutthaya and the Gulf of Thailand. The river (Figure 7) serves as the export pathway for teak and rice. The Thai people have made use of the Chao Phraya and its canal system for fishing, recreation (Figures 8-16), drainage and as the source of water. The Chai Phraya River flows past Chai Nat the home of a government dam and a large irrigation system. The Tha Chin River is the major distributary of the Chao Phraya River (Figure 6). These rivers are interconnected and serve both for irrigation and for transportation.

Bangkok occupies an area of about 1540 km² near the southern margin of a low-lying flat, marine-plain termed the Central Lowlands. The upper central Plain begins (Figure 6) where the Ping, Wang, Yom and Bam rivers join. These four rivers combine to form the Chao Phraya River near Nokhon Sawan 240 km north of Bangkok. The modern Chao Phraya River has developed a 10 km wide meander belt in the Lower Central Plain. Its levees are poorly connected and low (Figure 17 and Figure 18) and cannot prevent flooding large bottomland area north of Bangkok (Figure 19) especially during monsoon flows.

The Chao Phraya is the river of kings and the city of Bangkok was designed to be seen by the people from the water. The Thai are river people (Figure 20) and the more congested the road traffic becomes, the more the people of Bangkok dream of returning to their river. Bangkok, a city with more than 15,000,000 people can be seen from the river. Older inhabitants in shadow of new concrete and glass high rises (Figures 21-23), are still living waterborne lives in stilt-houses (Figure 5), and on barges, dependent on the brown river for their washing, fishing and transportation (Figure 20). People living on barges, near Krung

Thep Bridge, trade-in charcoal and others work in rice houses. The loggers and teak traders market their goods around Krung Thon Bridge before it is milled and exported. South of Klong Doei the Chao Phraya River increases in width and banks are covered with greenery (Figure 24). The River banks between Bangkok and Pak Nam are used for commerce. Pak Nam, where many trawlers anchor, has important fish factories, a renowned wat and some good fish restaurants. Klong Doei (Klong Toey) is Bangkok’s international port (Figure 25 and Figure 26) where freighters load exports from Thailand. Pak Nam “River Mouth” of the Chao Phraya River is where it flows into the Gulf of Thailand. The 40 km river channel south of Bangkok is lined with harbor installations (Figure 26). The mouth of the channel requires frequent dredging and vessels are limited to 10,000 tons.

Land subsidence in Bangkok, Thailand is primarily caused by well pumping and has affected Bangkok for the past 50 years. The impact of the pumping is critical due to the flat low-lying topography and presence of a thick soft lacustrine clay layer which creates foundational engineering problems. Pumping has lowered the water table by as much as 65 m. In the 1980s the subsidence rate subsidence at a rate as high as 12 cm/yr. Bangkok is sinking and could be underwater in 15 years and there is concern that any action taken will be too late.

In 2011, 800 people were killed by flooding and 12 million others were adversely affected. Bangkok was underwater for months and the economy suffered a US $41 billion loss. Bangkok is facing multiple challenges. The mean sea level is predicted to rise 1 m according to the Intergovernmental Panel on Climate Change.

As waters rise the city is sinking and accelerating the process of disappearing living space. Currently Bangkok is 0.5 to 2.0 m above the water. The metropolitan area is sitting on marshland and resting on a layer of soft highly compressible clay. In addition to natural land subsidence, 5 decades of excessive groundwater pumping and rapid urban development have put pressure on the alluvial and lacustrine foundation. The 5000 tall building (Figure 3 and Figure 4), 9 million vehicles, roads and rail systems have contributed to the pressure.

Subsidence of Bangkok clay due to deep well pumping can be reduced or controlled through artificial recharge [5]. Metropolis, a flood-resistant community could provide the blueprint on how to keep the city above water. Low lying- communities could be elevated 5 m above water to reduce the problems of flooding, rising sea levels and land subsidence. Restored mangrove forests could filter water, absorb carbon dioxide, and provide residents with an elevated community without fear of being flooded or being submerged and green open space.

Experts suggest that unchecked urbanization and eroding shorelines will leave Bangkok residents in a critical situation. With the weight of people and infrastructure contributing to the cities gradual descent into the water, Bangkok has become a casualty of its own successful development. Making the situation worse is the canals that are used to traverse the city have been replaced by a network of roads and bridges. The canals (Figure 27 and Figure 28) had contributed to a natural drainage system of waterway pathways. Shrimp farms (Figure 29) and other aqua-cultural development have replaced the shore stabilizing mangrove forests.

The lowland areas of the Chao Phraya basin in central Thailand are freshwater swamp forest, a subtropical and tropical moist broadleaf forest. The area is 400 km north to south and 180 km wide and is in the Chao Phraya River basin (Figure 6). The original swamp forest was converted to rice paddies, other agriculture and urban areas such as Bangkok. Most of the original wildlife is gone, including the birds and fish [8]. Without urban development the area would probably consist of freshwater swamps inland and salty mangroves on the coast and river

estuaries. The primary remaining relic of that original landscape is Khao Sam Roi Yot National Park. The Chao Phraya basin has 280 species of fish. The main stem of the Chao Phraya River alone has 190 native fish species. Extensive habitat destruction (pollution, dams, irrigation and drainage) has occurred. Overfishing has also been a historic problem. In the past decade, the Thai Pollution Control Department (PCD) has reported that the Chao Phraya River and tributary water quality have deteriorated. The river system contains bacteria and nutrients (phosphates, phosphorus and nitrogen) pollution. Nutrient pollution accelerates algae growth which harms water quality, marine habitats and food resources for aquatic animals [8]. It also decreases oxygen needed for fish survival. The PCD findings rate water quality very poor and large amounts of wastewater were discharged into the rivers from agriculture, industry (Figure 30) and households.