The role of landslides in mountain range evolution

We review the role of landslides in current concepts of the topographic development of mountain ranges. We find that many studies in this field address basin- or orogen-scale competition between rock uplift and fluvial bedrock erosion. Hillslopes in general, and bedrock landslides in particular, are often assumed to respond rapidly to incision and development of the fluvial drainage network. This leads to a one-sided view of the geomorphic coupling between hillslopes and rivers that emphasizes the fluvial control of hillslopes, but ignores the alternative view that landslides can affect the fluvial network. There is growing evidence that landslides are a dominant source of sediment in mountain belts and that they exert a direct geomorphic control on fluvial processes. Landslides can influence the river network in a variety of ways, from determining basin area and drainage divide positions, to setting streamwise variations in sediment load and calibre. The geomorphic legacy of large landslides on hillslope and channel morphologies may persist for up to 10(4) yr, adding considerable variability to fluvial erosion and sedimentation patterns over these timescales. We identify a number of questions for future research and conclude that a better understanding and quantification of the geomorphic feedbacks between landslides and river channels builds an important link between short-term (<10(1) yr) process studies and long-term (>10(5) yr) landscape evolution models. (C) 2009 Elsevier B.V. All rights reserved.