Slope processes

Mass movements like landslides, mudflows and debris flows are a common feature of many alpine environments, especially after intense rain. Their greater frequency and influence in alpine environments as compared to lowlands is easily understood given the steep slopes in high mountain systems.
 

Is the vegetation of importance?

Vegetation effectively impedes erosion, stabilizes slopes and increases the water-holding capacity of soils. After destruction of the vegetation cover (e.g. by road construction) susceptibility to mass movements is enhanced.

1) Landslide due to unstable substrate, Biet (Schwyz), Switzerland (148K)
2) Soil slides after road construction, Oberalppass, Switzerland (119K)

Mass movements of material due to mudflows, debris flows and landslides destroy the vegetation locally and create a mosaic of new conditions:
In the scar of a mudflow or landslide bare substrate is exposed, and little soil cover may be left. In such areas vegetation development takes the form of a (primary) succession.
In the deposition zone, the vegetation may be periodically covered over by mud and debris. On the other hand, fragments of upslope vegetation that were carried with the mudslide may survive and expand in the deposition zone.

The surface of a mudflow is exposed to more severe microclimatic conditions (wind exposure, freeze-thaw etc.) than the surrounding intact vegetation. Often there are also differences in the edaphic conditions between the mudflow and the undisturbed area, e.g. the soil nutrient content may be lower in the mudflow. These conditions may prevent rapid revegetation.

3 - Deposition of soil and vegetation fragments (119K)

Landslides and mudflows often have their origin in the alpine zone, but may impact upon areas far below, especially after deforestation; they can therefore be a hazard to human life and property.

29 August 2011
© ALPECOLe 2002-2007