Quantifying the role of vegetation in slope stability: A case study in Tuscany (Italy)

Vegetation significantly affects hillslope hydrological and mechanical properties related to shallow land-
slide triggering. In view of the complexity of soil plant hydrological interactions, the quantification of root
mechanical reinforcement remains a challenge. Herein we present a back analysis of mechanical stability
criteria related to a well-characterized vegetated shallow landslide in Italy, focusing on the quantification
of lateral and basal root reinforcement. Lateral root reinforcement is included in slope stability estimates
by adding a stabilizing force proportional to the scarp surface and root distribution. This stabilizing force is
added to the force balance equation for the infinite slope model for different landslide shapes and dimen-
sions. To quantify root reinforcement, we use the Wu model and the fiber bundle model (WM and FBM,
respectively). Implementation of the latter model allows the quantification of the stress–strain behaviour
of a bundle of roots for different root distributions and mechanical properties. Results of these models
are compared highlighting key differences between the two approaches. Calculations using the FBM can
explain the overestimation of lateral root reinforcement using WM and the commonly observed overes-
timation in the factor of safety. The model also quantifies the displacement-dependent behaviour of root
reinforcement on vegetated slopes. Lateral root reinforcement can strongly influence the stability of slopes
up to a certain area (1000–2000 m 2 ). The magnitude of this stabilizing effect depends on parameters such
as inclination, soil mechanical properties, and root distribution.


Ecological Engineering (2010)
Volume: 36, Issue: 3, Publisher: Elsevier B.V., Pages: 285-291
ISSN: 09258574
DOI: 10.1016/j.ecoleng.2009.06.014