Aug 27, 2025 07:38 PM
Deep gashes are tearing through cities, swallowing houses and displacing vast numbers of people
https://www.nature.com/articles/d41586-025-02745-x
INTRO: Deep gashes are tearing through cities, swallowing houses and displacing vast numbers of people 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”.
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.
In 99% of cases, the gullies had expanded by at least 10 square metres between 2004 and 2023. The average gully was 253 metres long and 31 metres across at its widest point, and nearly all of them were linked to the road network. “The water cannot infiltrate, and it concentrates along these roads which basically become big canals that turn into rivers,” says Vanmaercke... (MORE - details)
https://www.nature.com/articles/d41586-025-02745-x
INTRO: Deep gashes are tearing through cities, swallowing houses and displacing vast numbers of people 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”.
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.
In 99% of cases, the gullies had expanded by at least 10 square metres between 2004 and 2023. The average gully was 253 metres long and 31 metres across at its widest point, and nearly all of them were linked to the road network. “The water cannot infiltrate, and it concentrates along these roads which basically become big canals that turn into rivers,” says Vanmaercke... (MORE - details)