Land characteristics and management factors involved in landslides

Processes involved:

Landsliding occurs when the shear forces exceed soil/regolith strength; this generally occurs when soil/regolith strength is reduced by an increase in water.

Processes involved are:

• infiltration ofwater
• wetting of basal plane
• saturation of soil (mudflow)
• shearing and movement of soil mass by gravity

Other processes that may be involved include:

• loading of soil mass resulting in an increase in shear strength
• removal of material from slope toe resulting in reduced slope support

Types of landslides covered by this table are:
- rock and earth slides
- earth flow (downslope movement of unsaturated soil and weathered rock on a lubricated basal shear plane)
- mudflow (movement of saturated soil and rock)
- combination slide/flows

	Land characteristics affecting processes	Factors affected by land characteristics	Management factors that modify land characteristics
Vegetation	- leaf area, rooting depth perenniality - total leaf area and canopy type - root depth and mass	Transpiration and hence soil water content Volume of water held by canopy and hence volume available for infiltration Anchorage of soil by roots harvesting	All aspects of the vegetation are affected by selection of species and control of biomass by practices such as cultivating clearing trafficking fertilising grazing trampling burning
Climate	- seasonal rainfall/evapotranspiration regime	Soil water content
Geology	- perviousness of rock or unconsolidated sediments - wet strength of rock/regolith - angle of dip	Soil water content Shearing tendency Shearing tendency
Topography	- slope degree - microrelief and position in landscape	Lateral gravitational component Run-on, site drainage and hence soil water content
Soil	- topsoil permeability - presence of slowly permeable layer - cohesion of particles/aggregates including tendency to slake and disperse - depth - clay mineralogy	Infiltration/run-off ratio Water content of soil immediately above layer Soil strength Soil water content Soil strength	Compaction and soil disruption by stock and vehicles, and by cultivating, will affect profile permeability

Aldrick, J.M. et. al. (1988). A study of the Land in the Catchment of the Gippsland Lakes. Department of Conservation Forests and Lands, Victoria

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