“Dam construction upstream is one of the biggest triggers,” says Professor Zheng. The decrease, which is seen in a majority of river deltas worldwide, is causing the delta to retreat. “The effects of the decreasing sediment load are not yet fully understood,” he says, “but they are certain to be serious.” Unique approach In their research, Professor Zheng and Dr Hoitink focus on bifurcations in the river deltas: the points where a river splits into smaller channels. “We look at how a bifurcation developed and what this means for sediment discharge,” says Professor Zheng. “We want to know how a change in the bifurcation upstream effects water levels in the mid-stream and downstream areas of the deltas. Our approach is unique in the world.” More than fifty years of research data on both deltas is available for analysis. Professor Zheng explains: “We also do field research at the bifurcation of the North and West rivers in the Pearl River delta, to collect information on discharge, water level, current velocity, and sediment concentration. Ultimately, we hope to understand how runoff and sediment are changing due to both climate change and human activity.” That understanding can then lead to a model that helps predict future changes in water levels, in sediment transport, and in the bottom topography of the river channel networks. Focus The project is Professor Zheng’s first cooperation with Utrecht University. “It’s a very good academic programme,” he says. “We exchange not just people but also ideas, research, and knowledge. That allows us to focus on very special issues and locations in both China and the Netherlands. Without support from the NSFC-NWO Programme, cooperation would not be as close.” The Chinese government is very interested in the project, says Professor Zheng. “Flood defences were built to withstand oncein-a-century floods, but now we see the risk of those floods occurring once every fifty years. The Netherlands also needs to
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