The Pearl River Delta is becoming increasingly densely populated, but is extremely sensitive to flooding. This is a recipe for trouble. Dutch and American strategies could help more resilient design schemes to be achieved, as Dai Wei observes in his doctoral research.

The Pearl River Delta (PRD) is one of the most urbanised areas on earth. The highly densified megacities of Guangzhou, Shenzhen and Zhongshan are home to almost sixty million people, in an area one-third the size of the Netherlands. “After forty years of rapid urbanisation, important supply and discharge routes of the water system have been blocked,” says Dai Wei. "Climate change will inevitably lead to major flooding problems."

In 2018, typhoon Shanzhu caused 20% of the vulnerable region to be flooded, and if sea level continues to rise in the coming decades, the frequency of flooding will only increase. The big question in this regard is what strategies Chinese planners and designers can develop, besides building higher dikes.

In his doctoral research, Wei looked at how other deltas are tackling the challenges. In his opinion, the Dutch approach called 'Room for the Rivers' is very promising. The essence of this approach is to create extra space between the fluctuated river and the dike, which results in increased space when water levels are high.

In places where this is possible, this strategy could also offer solutions in China. Unfortunately, it is not only the fluctuated river that poses a threat, but also the sea. Moreover, land is scarce in the PRD, which is why many buildings have been built in the wrong places. “After forty years of urbanisation, the green-blue infrastructure is fragmented,” says Wei. “There are houses, offices and dikes in places where the water naturally wants to flow."

He used computer simulations to map out the area where the problems lie. His conclusions show that the PRD needs more ditches and channels, which need to be well connected in order to drain excessive water effectively. An example can be taken from New Orleans, another delta that he included in his research. After Hurricane Katrina, the capital of Louisiana tackled its water challenges by redesigning the entire water system. Not only were the dikes tackled, new sewers and canals were also constructed.

Chinese planners and designers need to use a wide range of strategic measures to achieve more resilient urban design schemes, says Wei. They should look beyond economic interests and take natural conditions into account more than before. What routes does water naturally take and which estuaries are important for ensuring the ecological functions of an area? Without recognising this underlying structure, it is difficult to arrive at a robust design that is adaptable.

Wei advocates clearer land use rules that clearly delineate which areas are suitable for housing, agriculture, nature or coastal development. He also argues for “transregional hydro-ecological corridors” and buffer zones along the coast.

In addition to this, better forecasts of the consequences of climate change are needed. Wei: "It is useful in urban planning if the map shows where floods might occur in the year 2100."

Published: March 2021

More information

• PhD thesis 'Spatial Planning and Design for Resilience'