Published online by Cambridge University Press: 10 January 2011
Landslides are a dominant geomorphic process affecting mountain slopes worldwide (see also Chapters 6 and 8). They represent a major sediment source that can supply a large amount of unstable debris to river channels and may affect the fluvial sediment yield. A distinctive part of the geomorphic evolution of active mountain belts, catastrophic landslides generally develop very rapidly so that they are among the most powerful natural hazards on Earth. By temporarily or persistently impounding river channels, they delay or block the delivery of sediments, affect the (dis)continuity of the cachment-scale sediment cascade, and exert a control over the fluvial valley systems (Hewitt, 2002; Korup et al., 2004). As a consequence, landslides may generate indirect hazards along fluvial systems, so that they represent a major threat to settlements, infrastructures and catchment management that may be felt over long distances from the unstable area (Plafker and Eriksen, 1978; Li et al., 1986; Costa, 1991; Korup, 2005; Hewitt et al., 2008). Their magnitudes, together with their causative factors, suggest the difficulty, if not the impossibility, of preventing and/or to predicting them.
In this brief overview, we shall firstly define catastrophic landslides and their geomorphic impacts, with special attention given to landslide-induced dams; we shall move on to their influence on sediment budgets, at local and basin-wide scales, before eventually considering a few actions that may help to minimize the vulnerability and risks for the potentially affected populations.