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For centuries, the Yangtze River has been China’s vital lifeblood, yet its floods have claimed countless lives. To tame its waters, flood-control systems have evolved from ancient dykes to the engineering marvel of the Three Gorges Dam.
But a new study has uncovered a paradox: some human interventions may have inadvertently worsened the very flood risks they were built to mitigate.
“We show that flood frequency peaked during the Little Ice Age [1500−1850] … and that human interventions, particularly embankments and lake reclamation, amplified climate-driven flood magnitudes,” a group of scientists in China and Europe wrote in a paper published on Monday in the Proceedings of the National Academy of Sciences of the United States of America.
The team reconstructed 500 years of Yangtze River flood variability since 1500 using lake sediment archives, historical documents and high-resolution climate reanalysis data.
They found that while climate remains the primary driver of flood occurrence, human interventions on the Yangtze River actually intensified climate-induced flood risks, rather than mitigating them.
Their analysis showed that constructing embankments and lake enclosures for agricultural use amplified the magnitude of 100-year floods, which have a 1 per cent chance of happening in any year, by 18 and 8 per cent respectively.
“Although large dams in the upper Yangtze River are widely recognised for reducing moderate flood peaks at local scales, the cumulative effects of river regulation on rare, extreme floods can be more complex,” they wrote.
“Extensive engineering works, including dams, levees, floodgates and channel modifications, can alter channel-floodplain connectivity and reduce the capacity of floodplains to store and dissipate floodwaters,” they wrote.
They said “floodplain storage loss and channel confinement have systematically intensified extreme discharge, offering a mechanistic explanation for why restoring lateral connectivity could help moderate peak flows”.


Lead author Yu Shiyong, a professor at Jiangsu Normal University’s School of Geography, Geomatics and Planning, said future flood control management should shift from containing floodwaters within river channels to basin-wide flood risk management.
“The core idea is not to eliminate floods, but to allow them to accumulate, divert and be released slowly in a predictable, controllable and minimally damaging space,” he said in an interview.
“An ideal flood control system for the Yangtze River should be a robust river and lake ecosystem with self-adjusting capabilities, rather than relying solely on ever-rising dykes.”
Given the “non-stationary nature of flood hazards”, Yu said future engineering blueprints must incorporate stress testing across a variety of climate projections.
“Our research does not suggest that all water engineering projects in history were counterproductive,” he said. “Embankments did protect many people and farmland in specific periods and locations with obvious short-term and local effects.
“The problem is that as embankments are continuously heightened and sever the connection between rivers and lakes, floodwaters that could have been dispersed and temporarily stored across vast plains are compressed into narrower river channels.
“While this reduces the frequency of small to medium floods in some areas, it can raise mainstream water levels and flood peaks, as well as shift the risk downstream, to the opposite bank or into the future.”
Yu envisions a hybrid future where dams, reservoirs and pumping stations coexist with green solutions such as wetlands and floodplain restoration.
“Priority should be given to expanding the natural flood storage space through rational land use planning in the Yangtze River basin to allow natural systems to absorb floodwaters first. For risks that are unavoidable and have severe consequences, high-standard engineering should be used for focused protection,” he said.

Applying this strategy, upstream mountainous areas should improve forest, wetland and watershed management, while midstream plains should restore lake and wetland storage functions to create flood storage zones, Yu said.
In areas where the river intersects with key infrastructure zones and heavily populated cities such as Wuhan, dams, dykes and drainage networks should be enhanced, he continued.
“Over-reliance on engineering can create a false sense of ‘absolute safety’, which encourages more population and assets to crowd into protected floodplains, making the consequences even more dire when a flood eventually exceeds the design standards,” Yu said.
Around 5,000 years ago, relatively mature water conservancy systems emerged in the middle reaches of the Yangtze River, including dams, dykes and reservoirs, Yu said.
“These projects combined flood control, water storage, water diversion and irrigation functions, showing that the ancient people’s approach to flood control had shifted from passive flood prevention to active regulation and utilisation of water resources,” he said.
Although other ancient civilisations developed their own flood control systems, including the Mayans and along the Nile, Mesopotamia and Indus valleys, China stands out with its immense scale and historical depth in flood control.
“The Chinese experience is unique in that our water management practices have an exceptionally long history, cover a vast area and have continuously entered into the national systems, social organisations and cultural memory,” Yu added.
He said that before the first dynasty was established, the legend of Yu the Great taming floods in the Yellow River basin embodied “the idea of controlling floods by dredging river channels and harnessing natural forces. Flood control also became an important cultural symbol of the nation’s formation and political order”.
Drawing insights from China’s history, Yu said the modern way to manage floods was to acknowledge that rivers had their own space and patterns.
“Truly modern water management is about scientifically determining which areas must be protected, which areas should be left flood-prone and when to store water and release it, while ensuring that the costs and benefits are shared fairly,” Yu added.


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Chinese scientists find some Yangtze flood controls may do more harm than good

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China

By compressing rivers and stripping away natural defences, human engineering may be worsening flood impacts, prompting a global rethink


By compressing rivers and stripping away natural defences, human engineering may be worsening flood impacts, prompting a global rethink.


United States

Chinese scientists find some Yangtze flood controls may do more harm than good

.css-1c6uqr6{color:inherit;font-weight:inherit;font-size:inherit;font-family:inherit;line-height:inherit;overflow-wrap:break-word;}By compressing rivers and stripping away natural defences, human engineering may be worsening flood impacts, prompting a global rethink

By compressing rivers and stripping away natural defences, human engineering may be worsening flood impacts, prompting a global rethink