Many might assume that we are powerless in the face of ongoing sea-level rise, and that the risk of flooding is inevitable near the coast. However, how governments choose to develop coastal regions is affecting exposure to flooding more than climate threats, according to a new study. The research analyses flood risk scenarios in China's coastal zone from 2020 all the way until 2100.
Across the world, coastal zones are on the front line of climate change. Increasing temperature drives sea levels higher, and more intense storms can cause extreme events, resulting in dangerous floods. Human activity such as groundwater extraction also makes much coastal land sink relative to sea level, further exacerbating the risk of floods.
At the same time, coastal cities are key hubs for global trade and have for centuries been heavily developed-placing people, infrastructure and assets in harm's way.
"The dominant policy is to develop coastal areas, then protect the land with, for example, sea walls. However, this approach is risky as sea walls fail to meet standards in many parts of China, and they can create a false sense of safety," says Murray Scown, associate senior lecturer at Lund University, and one of the authors of the study.
More than 700 million people live in China's coastal zone which includes megacities like Shanghai, in the Yangtze River Delta, with a population of almost 25 million, Guangzhou, a trade city in the Pearl River Delta, with roughly 19 million people, and the northern city Tianjin, which is home to roughly 14 million people.
The researchers identified four hotspots as being most at risk for floods. These places are both highly urbanised and very low lying: the three deltas of the Pearl, Yangtze, and Liaohe Rivers, as well as the Bohai Bay.
"We saw that while climate threats largely determine where floods could occur, coastal policies determine what could be flooded. In other words: it could be houses and people at risk, or agricultural land and nature reserves," says Murray Scown. "It's important to consider that after 2100, climate will have an increasingly large effect as well."
The researchers note that these findings are very positive as they highlight how strategic coastal planning can make a big difference for how to handle the impacts of floods.
"In any country, China included, there can be tensions between the need for economic development and ecosystem protection and climate action. Yet, there are many low hanging fruits; one of them is to ensure standards are met for sea walls, another is to ensure flood risk assessments are integrated into spatial planning," says Yafei Wang, associate professor at the Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences.
"Climate-smart policies and plans that consider the multiple interacting risk factors can greatly reduce how climate change impacts coastal areas. We hope this study underscores that," he concludes.
