Experimental evidence for hillslope control of landscape scale

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Science  03 Jul 2015:
Vol. 349, Issue 6243, pp. 51-53
DOI: 10.1126/science.aab0017

Landscape evolution in a sandbox

The long-term response of hills and valleys to changes in climate depends on a variety of physical factors. Sweeney et al. performed tabletop erosion experiments as a function of rainfall and uplift: variables that are impossible to precisely control in nature (see the Perspective by McCoy). Ridge and valley spacing are set by the balance of sediment moving down hillslopes or being washed out of valleys by rivers. Landscapes therefore evolve as a response to climate change altering erosion rates.

Science, this issue p. 51; see also p. 32


Landscape evolution theory suggests that climate sets the scale of landscape dissection by modulating the competition between diffusive processes that sculpt convex hillslopes and advective processes that carve concave valleys. However, the link between the relative dominance of hillslope and valley transport processes and landscape scale is difficult to demonstrate in natural landscapes due to the episodic nature of erosion. Here, we report results from laboratory experiments combining diffusive and advective processes in an eroding landscape. We demonstrate that rainsplash-driven disturbances in our experiments are a robust proxy for hillslope transport, such that increasing hillslope transport efficiency decreases drainage density. Our experimental results demonstrate how the coupling of climate-driven hillslope- and valley-forming processes, such as bioturbation and runoff, dictates the scale of eroding landscapes.

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