In southern China’s Pearl River Delta, eleven cities are currently merging to form one huge megacity. But as a result of investments from Hong Kong and Taiwan, over the last three decades the once rural area has been transformed into a booming factory for export goods – and an area about the size of Lower Saxony is now home to a population as large as Great Britain’s.
Today, the monsoon climate is already hard on the people living there. Compared to Hamburg, there is more than twice as much rainfall, most of which is concentrated in the six monsoon months. The damaging effects of regular flooding are further exacerbated by paved surfaces and channelized riverbeds. In addition, recurring typhoons lash the land with meter-high waves of seawater.
Will climate change worsen these threats? What adaptation strategies are available? This is the subject of my research at the Cluster of Excellence CliSAP, Universität Hamburg. Using historical measurements from the delta and a simulation model from the Max Planck Institute for Meteorology in Hamburg, I determined future scenarios for temperature, precipitation, sea level and tropical cyclones. According to these scenarios, the average temperature in the delta will rise by up to three degrees in the 21st century. Precipitation will become more extreme, i.e., more often unusually light or heavy. If greenhouse gas emissions go unchecked, the sea level could rise by up to a meter compared to the 2005 mark.
The result: the delta will experience more frequent and more severe flooding from the river, but also from the tides in the South China Sea, since almost eight percent of the area is three meters above sea level or less. And it is precisely here – in the flatlands – that the major industry and cities are located. The new coastal zones created through land reclamation are particularly at risk.
But floods will have different impacts in different places. Depending on their location and structure, cities vary in terms of their vulnerability. On the basis of statistical data, I first estimated the likelihood of flooding, which depends, for example, on an area’s height above sea level. In order to rate a city’s susceptibility to flooding, among other things I analyzed data on the population structure. The young, the elderly and the unemployed are especially at risk. I then considered the ability of cities to adapt to the flood risk. This can be determined on the basis of social aspects like per capita income. Hong Kong is a particularly interesting example. The peninsula faces serious risks – but as a business and financial metropolis also has the resources to take suitable preventive measures.
How will flood protection in the delta have to be adapted? Apart from conventional solutions like levees, the region above all needs “soft measures” that promote awareness of the dangers: a jointly developed climate strategy, more reliable weather forecasts, and official recommendations on what to do in case of a flood. Last but not least, social media could be used to provide real-time flood information.
Author: Dr. Liang Yang
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