Tiefe Schnittrissen durch Städte, Schlucken von Häusern und verdrängen eine große Anzahl von Menschen. Untersuchungen ergaben

Gigantic trenches known as gullies are opening up in cities in Africa, swallowing up homes and businesses, sometimes in an instant, a study has found1.

About 118,600 people, on average, in the Democratic Republic of the Congo (DRC) alone were displaced between 2004 and 2023, according to researchers reporting their findings in Nature.

Without urgent action, researchers estimate that hundreds of thousands of people across Africa are likely to be displaced within the next 10 years, including more than one-quarter of the 770,000 or so people in the DRC living in the expected expansion zone of these gullies.

“It’s an underestimated and severely under-researched hazard,” says study co-author Matthias Vanmaercke, a geographer at the Catholic University of Leuven (KU Leuven) in Belgium. It is caused by “a combination of natural and human factors”, he says, but this is “not at all unavoidable”.

Expanding gullies
Gullies are expanding across cities that are built on sandy soils and lack adequate drainage. When there are heavy rains, water accumulates on roads and rooftops. When the drainage systems are inadequate, the water finds its way into unprotected ground, carving deep holes that can stretch for hundreds of metres. Over time, the gullies swallow houses and other infrastructure, and sometimes even result in deaths.

Vanmaercke and his colleagues used satellite images taken between 2021 and 2023 to identify 2,922 urban gullies in 26 of 47 cities, covering a cumulative distance of nearly 740 kilometres. The team cross-checked these images with historical aerial photographs stored at the Royal Museum for Central Africa in Belgium and found that only 46 of the gullies were present in the 1950s. This “gave the first clear indication that this is indeed attributable to the ongoing urbanization”, Vanmaercke says.

[https://www.nature.com/articles/s41586-025-09371-7](https://www.nature.com/articles/s41586-025-09371-7)

It’s erosion. 

They’re building on sand with no drainage. This is the inevitable result. 

Build proper drainage systems and they’ll be fine.