The natural role of vegetation in controlling slope stability is evident in many different areas of the world. For example tree roots can have significant positive effects in terms of adding to the effective strength of the soils. However, what complicates this relationship is the changed hydrological parameterisation of the soil properties that vegetation provides (for example, by increasing the soil hydraulic conductivity).
In major projects as well as more routine maintenance considerations bioengineering is seen as a specific option to enhance slope stability. This can take the form of standard hydroseeding, as well as other more intricate species mixes on slopes:
To accommodate bioengineering CHASM includes a vegetation module which allows changes to be made to the effective soil hydraulic conductivity, the effective rainfall reaching the surface of the slope and the soil shear strength via root reinforcement.
Collison, A.J.C., Anderson, M.G. and Lloyd, D.M. (1995) Impact of vegetation on slope stability in a humid tropical environment: a modelling approach. Proc. Inst. Civil Eng. Water Maritime and Energy, 112, 168-175, (paper awarded the Trevithick Premium Triennial award for a research paper published by the Institution of Civil Engineers in 1996).