The Pearl River Delta is a dynamic area undergoing rapid urbanisation, but this is largely taking place without adequate maps. That is why PhD candidate Liang Xiong has developed a set of maps himself that show in great detail where there is a risk of flooding and where it is or is not wise to build.
China does have detailed maps, but they are held under lock and key by the military. Refined topographical knowledge is considered strategic information in the People's Republic and is therefore a state secret. In consequence, the best maps available are very low-resolution. And that's a problem in the Pearl River Delta. “If you don't know how water, flood protection and urbanisation work, it is hard to operate here as an urban planner,” says Liang Xiong.
Comparing delta's
The PhD student made his own maps by comparing the Chinese delta with similar areas. Although the Meuse, Paraná, Mekong and Mississippi deltas show different flow and development patterns, there are also many similar landscape patterns. On the one hand, the area in which major Chinese cities such as Guangzhou, Shenzhen and Foshan are located is the catchment area of a large river, comparable to the Mississippi Delta. On the other hand, the area has to deal with tidal ebb and flow, comparable to the Meuse Delta.
Xiong compared the areas by looking at different layers that can be distinguished: the landscape elements, the infrastructure and the buildings. He used geodata from the last 6,000 years to clarify the development patterns and to be able to colour in which lower-lying areas are vulnerable to flooding.
What did that yield? An atlas that makes clear that urban development in the Pearl River Delta is not moving in the right direction. In recent decades, houses and factories have been haphazardly built in locations with a high risk of flooding. Given the countless construction projects that are being planned, it is only likely to get worse in the coming years. So it is high time for China to invest in adaptive building forms or in restoring original landscape patterns, Xiong observes. "My maps can help to reverse the negative trend."
Foshan
Xiong held a number of workshop discussions with urban planners and local authorities, who made their topographical knowledge available to improve the maps as far as possible. A finer resolution than six square kilometers is not permitted by law. Nevertheless, Xiong was able to use all the available data to create a detailed map by zooming in on one area of 40 square kilometres around the city of Foshan. This showed that small-scale developments are inextricably linked to large-scale delta developments.
Does the improved map bring the solution within reach? Not immediately. The Chinese government has yet to learn to enter into dialogue with local stakeholders, Xiong observes. A lot of information is still hidden from the public, for fear that public participation will slow down developments.
Another complicating factor is that in the Chinese planning system, water management and urban development are still strictly separated. They do not work together and they each use their own maps. “My project should contribute to getting both parties on one map,” says Xiong.
Nevertheless, local authorities do see the usefulness of the map project. After his PhD, Xiong has been invited to perform on-site risk analyses based on local data. "On the condition that all results remain secret."
Published: December 2020
Source of used maps in image:
U.S. Army Map Service (1954) ‘China AMS Topographic Maps,1:250000, Series L500’. Washington, D.C.
Zhao, H. (1982) ‘珠江三角洲的形成和发展’ Forming and Development of Pearl River Delta, Acta Oceanologica Sinica, 4(5), pp. 595–607
Meer informatie
- PhD thesis 'Pearl River Delta: Scales, times, domains'