Mud Barriers Along Rivers May Increase Flood Risk: Study

乍看上去

• A satellite photo of the Yellow River delta in China revealed that building mud barriers alongside rivers to prevent floods may have the opposite effect.
• Flooding is a growing threat due to more extreme and frequent rainfall due to global warming.
• Analysis of the Yellow River in northern China found that flooding was rare between 12,000 and 7000 years ago.
• Flooding rates substantially increased around 1500 years ago when people began building mud ridges along the river.
• Computational modelling of the river indicates that riverside mud barriers may lead to a greater build-up of sediment at the bottom of the river, making floods more likely.

细节

A satellite photo of the Yellow River delta in China

A satellite photo of the Yellow River delta in China taken by LWM/NASA/LANDSAT/Alamy has revealed that building mud barriers alongside rivers to prevent floods may have the opposite effect.

Flooding is a growing threat

Flooding is a growing threat to millions of people worldwide due to more extreme and frequent rainfall due to global warming.

Shi-Yong Yu at Jiangsu Normal University in China and his colleagues analysed the frequency of floods on the Yellow River in northern China.

The team compiled a timeline of floods on the river from the past 12,000 years using historical records and data from river sediments.

They found that flooding was rare between 12,000 and 7000 years ago, with an average of just four floods every 100 years.

Human activities and flooding

The researchers compared the timeline of floods with records of human activities, such as agriculture, and found that floods became more common following the expansion of local human settlements around 4000 years ago.

Flooding rates substantially increased around 1500 years ago, when people began building mud ridges along the river as flood barriers called levees.

The analysis suggests that flooding occurred 10 times more often in the past 1000 years compared with before the start of ancient Chinese civilisation.

It indicates that human activities, primarily the use of artificial embankments, drove about 80 per cent of this increase in flood rates, with the rest attributable to natural changes in the climate.

Computational modelling of the river

Computational modelling of the river indicates that riverside mud barriers may lead to a greater build-up of sediment at the bottom of the river, lifting the riverbed and raising water levels, making floods more likely.

In response to this, the Chinese government has introduced a policy to conserve wild riverside vegetation since the early 1980s, which helps prevent soil from falling in and may be a better approach.

The research suggests that other countries should also shift away from artificial embankments and instead focus on conserving wild riverside vegetation in order to reduce the risk of flooding.