Journal of Geophysical Research: Earth Surface
© 2014 American Geophysical Union
Impact Factor: 3.174
ISI Journal Citation Reports © Ranking: 2012: 23/170 (Geosciences Multidisciplinary)
Online ISSN: 2169-9011
Associated Title(s): Journal of Geophysical Research
The effect of sediment on mountain river erosion
Mountain uplift and subsequent water-powered erosion are powerful and persistent processes shaping the landscape, and understanding the interactions between these two processes has been an area of active research for the past 2 decades. The rate of river erosion has long been considered to scale with stream power, the potential energy dissipated by the water as it flows downhill. While widely used, this model has been tested in only a limited number of situations, sometimes with little success. The stream power model, in which erosion rates scale with the area of the upstream drainage basin and the slope of the stream, makes no account for the amount of sediment in the river. Sediment can increase erosion when the overall sediment levels are low or prevent it when the sediment load is high and the sediment can form an armor-like cover on the river bed. Using numerical simulations that implement four different river erosion processes, each of which deals with the effects of sediment transport on stream incision in a different way, Gasparini and Brandon (2011) found that the stream-power model works very well but only as an empirical representation of the river erosion process. The researchers found that the models are sensitive to the spatial distribution of erosion in the landscape and to the downstream distribution of sediment load. Many mountains tend to grow fastest at their centers, producing a large amount of sediment that is sent downstream. Water-borne sediment in the upstream part of the mountain increases the ability of the flow to chip away at the riverbed, but downstream, away from the fast uplifting part of the mountain, this sediment load accumulates and forms a protective layer on the channel bed, reducing the amount of erosion. This natural feedback loop likely supports the erosion patterns observed in many natural mountain ranges and can affect the details of the empirical stream-power relationship.