Scientist to tackle China's 'sinking cities' problem

The results of the research will include dramatically improved geological data for Shanghai as well as important software technology developments that can be applied to other cities in China and the world.

Shanghai, one of the most densely-populated cities in the world, is believed to be sinking at an average rate of between 2cm to 4cm a year, putting pressure on underground pedestrian and railway tunnels and building foundations.

Subsidence can lead to the collapse of tunnels and nearby buildings.

In 2003 subsidence was blamed for the collapse of an eight-storey building in Shanghai’s inner city Bund region, which is known for its iconic commercial real estate.

Shanghai, like several other coastal cities in China, is built on marshy soil, making it vulnerable to sinking.

The pumping of groundwater to cater for a massive, growing population has been a significant contributor to subsidence. The problem has been exacerbated by the country’s decades-long building boom amid rapid urbanisation, notes Dr Sowter, who supervises UNNC engineering students at the PhD level.

The authorities in Shanghai and elsewhere along China’s east coast are concerned about their sinking cities, which are also vulnerable to rising sea levels as the polar caps melt from global warming.

“The authorities have continued to enlist state-of-the-art technology to help them in this battle. This NSFC project brings them up-to-date with the latest scientific developments,” said Dr Sowter.

The UNNC scientist’s sophisticated software analyses satellite images gathered over several years and can reveal how much land has moved, in millimetres, across the entire city.

Dr Sowter is working in collaboration with Shanghai’s Tongji University, which is gathering ground information to confirm the results of data gathered from space.

“We are advancing and refining existing computer programmes so that we can identify risks with greater confidence of the accuracy of the results. Rather than just measuring the problem, we are also improving the models in order to make predictions,” he said.

“This technique is just one tool in the risk-assessment box. It allows us to map and identify priority areas,” said Dr Sowter.

“It is based on the use of radar satellites that are constantly monitoring and measuring the earth’s surface from up in space. China is about to launch its own radar satellite to further enhance its disaster management and response satellites, which will be an important addition to its humanitarian mission,” he noted.

Dr Sowter said the technology he is developing can be applied to other risks associated with land, like earthquake zones, high-risk flood areas, land deformation from mining, and glacier movements. It can, for example, help authorities prevent landslides by detecting where land is starting to move at the stage when changes are slight.

The University of Nottingham Ningbo, China scientist has also commenced research on the coastal city of Ningbo to assess the extent to which it might be sinking.

An underground rail system is being constructed to accommodate the estimated 8m-plus population of greater Ningbo, which like Shanghai has developed rapidly and is on water-logged land.

Dr Sowter said: “The authorities in China are very aware of the issues and have been actively working to reduce risks. For example, our latest findings show that the Shanghai authorities are doing an excellent job in making sure skyscrapers are not being built in the highest-risk areas.

“In some areas the land has risen, which is a sure sign that large constructions have been reinforced by builders who are fully aware of the subsidence problem,” he said.

However, a snapshot of results for Shanghai’s PuDong International Airport shows the picture is different for its newest terminal, opened in March 2008.

“What the green dots are telling us is that Terminal 2 is likely to be subsiding at a rate of around 2.5mm a year compared to Terminal 1, which opened in 1999,” said Dr Sowter.

“It probably indicates settling of the buildings following construction but, certainly, the airport authorities should be made aware of this,” he said.

Also taking strain on the Shanghai soil, it seems, is one of the city’s major traffic intersections.

“An elevated road, the Zongshan Bei Lu cuts across some of the areas that are subsiding the most in Shanghai and contains a major elevated junction, Gonghe Xin Lu overpass.

“The possible subsidence here is only about 3mm/year and is very well known and understood by the authorities. However, the maps that we produce around areas like these can only help to improve the monitoring and prediction of any risks,” said Dr Sowter.

Professor Nabil Gindy, Vice-Provost for Research and Dean of the Graduate School at UNNC, said: “The University is delighted to be involved in collaborative research projects like these that have important positive outcomes for the communities around us.

“We are committed to fostering the broader social good, at the local and national level in the countries in which we operate, as well as internationally,” he said.

Professor Gindy added: “We aim for all our research to be highly relevant for current challenges and to make a significant global impact. Our vision is to be recognised around the world for our signature contributions and innovation in developing technologies.”

The University of Nottingham Ningbo, China was the first Sino-foreign university to open its doors in 2004. The English-medium university campus has a growing research capability.
The University has received acknowledgement from the country’s highest authorities that it is playing a leading role in world-class research in science and technology.
It has been designated as an international science and technology co-operation base — an award given by the Chinese government only to universities and companies that have had significant success in international research collaborations.
Two of the University’s laboratories have been awarded the prestigious “key laboratory” status for the important work being conducted on improving and developing new green manufacturing and sustainable energy technologies.

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Notes to editors: The University of Nottingham, described by The Times as “the nearest Britain has to a truly global university”, has award-winning campuses in the United Kingdom, China and Malaysia. It is ranked in the UK's Top 10 and the World's Top 75 universities by the Shanghai Jiao Tong (SJTU) and the QS World University Rankings.

The University is committed to providing a truly international education for its 39,000 students, producing world-leading research and benefiting the communities around its campuses in the UK and Asia.

More than 90 per cent of research at The University of Nottingham is of international quality, according to the most recent Research Assessment Exercise, with almost 60 per cent of all research defined as ‘world-leading’ or ‘internationally excellent’. Research Fortnight analysis of RAE 2008 ranked the University 7th in the UK by research power.

The University’s vision is to be recognised around the world for its signature contributions, especially in global food security, energy & sustainability, and health.