Monday, August 13, 2007

Ancient urban sprawl surrounded Cambodia's Angkor

Sprawling Angkor engineered its own end

August 14, 2007
Leigh Dayton, Science Writer
The Australian

A NEW archaeological map confirms that Angkor in Cambodia was the biggest pre-industrial city ever founded and provides tantalising clues about its mysterious demise 500 years ago.

Sprawling about 1000 sq km out from its central religious heart with its legendary temples and reservoirs, known as Angkor Wat and Angkor Thom, the vast city was roughly the size of Singapore, or greater Sydney from the coast to Parramatta.

Angkor itself was the capital of a sparsely settled agricultural empire that stretched from Thailand in the north, across the flood plains, and southwards towards the Cambodia-Vietnam border.

"Like the modern world there was a vast expansion of the urban environment out into the rural world," said Sydney University archeologist Roland Fletcher, founder and co-director of the Australian, French and Cambodian Greater Angkor Project.

A goal of the project was to nail down the geographical extent of the city. According to GAP deputy director Damian Evans, a Sydney University doctoral student, the new map does just that.

"This is the culmination of about 15 years of mapping work," said Mr Evans, who led the effort to integrate the data into the map, revealed overnight in the US journal Proceedings of the National Academy of Sciences.

Sources included hand-drawn maps, ground surveys and airborne photography provided by GAP members and ground-sensing radar images provided by the US space agency NASA.

Not only does the map reveal the extent of Angkor -- a Khmer kingdom from the 9th to the 15th centuries -- it pinpoints over 1000 new water storage ponds and more than 74 long-lost temples. In its heyday, as many as 500,000 people may have lived in the sprawling low-density city. The map will allow scientists to tighten population estimates.

According to Mr Evans, the map also provides hard evidence backing the controversial hydraulic hypothesis.

This states that Angkor was linked by a vast network of irrigation channels, storage ponds and reservoirs. As the city grew, land was cleared, causing soil to clog the channels. Eventually, it became too expensive and complicated to keep the system free-flowing and it collapsed, taking Angkor with it.

The city, in essence, engineered its own demise by disrupting the environment.

"We can certainly see there were problems in the hydraulic networks," said Mr Evans.

"There's evidence of water courses punching through dykes and inadequate attention (to maintenance)."

Said Professor Fletcher: "It's a cautionary tale for the modern world."

Ancient urban sprawl surrounded Cambodia's Angkor

August 13, 2007
By Tan Ee Lyn

HONG KONG – Archaeologists have published a new map showing an extensive ancient settlement surrounding Cambodia's Angkor Wat that supported large numbers of inhabitants before and after the famous temple was built.

Now obscured by vegetation and low-lying clouds, the ruins spread over 1,000 sq km and were made up of thousands of houses, roads, manmade ponds and canals, researchers from Australia, Cambodia and France said in the latest issue of the Proceedings of the National Academy of Sciences.

'We now know that instead of being just (a collection of) temples, Angkor was actually a continuous and interconnected network of temples and small scale residential features like small village ponds, small village temples as well,' Damien Evans of the Archaeological Computing Laboratory at the University of Sydney told Reuters in a telephone interview.

'Very little remains now, they are just piles of brick ... a thousand years ago (it) would have been a huge and popular city, full of life, rather than this image of temples in a jungle.'

Angkor Wat was built in the early 12th century, while the settlement existed between 500 AD and 1500 AD, Evans said.

'What we can see, even on a preliminary basis, is that several hundred thousand people must have lived in the Angkor area ... which is defined by the infrastructure, the roads, the canals, huge embankments,' he added.

Using hand-drawn maps, ground surveys, satellite imagery, aerial photography and ground-sensing radar provided by NASA, the researchers identified what they believed to be more than a thousand former manmade ponds, temples and moats – all of which were now replaced by vegetation.

Ranging from 20 metres to 8 km long, the ponds were used for drinking, irrigation, livestock and other domestic purposes and were especially crucial for the dry season.

'The slightly lower elevations of the rice fields in the former moats and reservoirs ... result in different stages of rice maturity and in differential levels of soil moisture content, which strongly affect the returned radar signal,' Evans said. 'You get more mature rice in these wetter areas.'

The researchers believe the settlement was abandoned around 1500 AD because of overexploitation and deforestation.

'What our work proved for the first time was that Angkor certainly was large enough and its water management system was complex and extensive enough to have created very serious environmental problems,' Evans said.

'In such situations, infrastructure becomes very important and increasingly complex and difficult to maintain.'

Future studies will look at how serious these problems were and if the inhabitants were able to deal with them.

Radar discovers temples in ancient city

Tuesday, 14 August 2007
University of Sydney (Australia)

Australian researchers using NASA technology to map the medieval city of Angkor have discovered at least 74 new temples.

"We've mapped a huge settlement beyond the main temples at Angkor using radar imaging and other satellite data," said Damian Evans, a deputy director of the University of Sydney-based Greater Angkor Project.

"This is the first time a complete, detailed and comprehensive map of Angkor has been presented," he said.

The research and images will be published this week by the PNAS, the world's most-cited general science journal, published by the National Academy of Sciences of the USA.

Carpeted with vegetation and obscured by low-lying cloud, the ruins spill over 1,000 square kilometres outside the World Heritage site, located in present-day Cambodia, and are linked by a complex water management system.

Mr Evans and colleagues from Australia, Cambodia, and France have worked for years to integrate information from hand-drawn maps, ground surveys, airborne photography, and ground-sensing radar provided by NASA.

"The radar can sense differences in plant growth and moisture content that result from topographical variations of less than a meter," Mr Evans said.

"We have identified over a thousand new man made ponds and at least 74 long-lost temples, by correlating the radar data with on-the-ground sampling."

One single hydraulic system links the entire network, which appeared to provide Angkor's citizens with a stable water supply despite the unpredictable monsoon season.

The system, thought to be purely decorative and ceremonial by many scholars for the past 30 years, may actually have been used for irrigation and the intensification of rice agriculture.

Mr Evans said there "are also signs that the large-scale city engineered its own downfall by disrupting its local environment by expanding continuously into the surrounding forests and exposing the water management system to increased sedimentation and erratic water flows."

This caused a radical re-engineering of the landscape, and increased reliance on a massive and delicately balanced infrastructural network.

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