糖心视频

Deep, gigantic cracks in the Earth known as gullies are tearing through African cities, swallowing up houses and streets, destroying infrastructure and displacing tens of thousands of people. Left unchecked, this new geological hazard could force millions of people to abandon their homes in the coming decades.

A new study in the journal Nature, which focused on the Democratic Republic of the Congo (DRC), highlights the scale of the problem. Scientists mapped 26 cities in the central African country and found 2,922 massive gullies. These deep and widening chasms often appear without warning, swallowing up everything in their path.

According to the researchers, they caused an estimated 118,600 people to abandon their homes between 2004 and 2023. And the problem is getting worse. In just over a decade, the number of people living in areas at risk of being swallowed has doubled from 1.6 million in 2010 to 3.2 million in 2023.

"Our results demonstrate the massive magnitude of the problem of UGs (urban gullies). With more than half of the investigated cities affected and more than 2,900 gullies mapped, UGs are a widespread phenomenon," the researchers commented in their paper. "The threats and impacts of UGs are likely to greatly increase over the next decades."

So what is causing the problem? According to the study's authors, gullies are the result of a mix of natural erosion and human activities. They tend to form in areas with steep slopes and sandy soils, which are easily washed away by rain. Rapid, unplanned city growth and a severe lack of proper infrastructure make the situation worse.

During heavy rains, water accumulates on road surfaces and rooftops instead of being absorbed into the ground because of inadequate drainage systems. So it concentrates into powerful streams that carve deep channels in unprotected land. These channels can grow to be hundreds of meters long and spread through neighborhoods, destroying buildings, sometimes with fatal consequences.

Solutions and outlook

While this study only looked at the DRC, urban gullies are a growing problem in many other tropical cities across the Global South. The situation is likely to become more severe due to climate change, which may lead to more intense rainfall events.

The research team believes that solutions must include better awareness and a greater focus on prevention. They advocate a mix of strategies, including improving urban planning to ensure new areas have proper drainage and infrastructure, vegetation and structural barriers to stabilize the soil and managing rainwater runoff before it becomes a devastating force.

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