23 Apr

Topography Tuesday: Urban Gully Erosion

By Phoebe Hill

Gully erosion is the most aggressive form of soil degradation caused when surface water pools and forms a stream, eroding away massive amounts of sediment in a short period of time. In tropical urban areas across the Global South, poor urban infrastructure, intense rainfall, and deforestation put densely populated areas at risk of such geohazards. 

Brazilian city of 70,000 people is set to be SWALLOWED by the earth due to  de-forestation | Daily Mail Online

Both Latin America and Africa are worst affected by urban gully erosion. In the Brazilian city of Buriticupu, more than 100 families were forcibly relocated as widening gullies threatened homes. In the capital city of the Democratic Republic of the Congo, Kinshasa, 60 people lost their lives when a large gully opened up during a heavy rain event in 2022. Such hazards impede urban development and threaten the safety of residents.

Buriticupu: a town with a chronic gully and landslide problem in Brazil -  The Landslide Blog - AGU Blogosphere

Urban gully erosion is only predicted to worsen with changes to global weather associated with climate change. Scientists predict a 10-15% increase in rainfall intensity across the globe before the end of the century. Such increased severity and frequency of extreme rainfall events will affect cities currently without proper drainage infrastructure for surface water, leading to a heightened threat of gully erosion. Deforested areas will be further susceptible as raindrops fall unimpeded upon soil and are therefore more easily able to erode away large quantities of sediment. 

Experts insist that actions can be taken to protect urban populations in gully-susceptible areas from such devastating erosion. The creation of new urban infrastructure to efficiently drain surface water is crucial for creating safer cities. Moreover, focusing on vegetation restoration and reforestation will enhance natural resilience in the face of growing climate extremes.