Credit: © Will Ouimet

Incision by rivers in rapidly uplifting landscapes leads to steep hillslopes and frequent landslides. A recent study finds that such landslides, in turn, affect landscape evolution by damming the rivers for up to thousands of years and thereby slowing the rate of river incision.

William Ouimet from the Massachusetts Institute of Technology, USA and colleagues1 conducted extensive fieldwork along the Dadu and Yalong rivers that incise the eastern margin of the Tibetan Plateau (Sichuan, China). They found evidence for landslides at various locations along both rivers. Using their data on locations, sizes and other physical characteristics of the landslides, the researchers developed a numerical model aimed at quantifying the influence of landslides on bedrock river incision and landscape evolution. They suggest that the number and height of landslide dams, averaged over the length of a river, is governed by how frequently large dam-forming landslides occur and the time taken by the river to incise through the dams.

The results indicate that both infrequent deposition of slowly eroding landslide dams and frequent landslides producing short-lived dams lead to a reduction in the long-term rate of river incision.