Some Remarks on the Possible Effects of Vegetation Cutting on the Triggering of Debris Flows in Central Italy

The paper focuses on a preliminary study of the effects of vegetation cutting on the activation of debris flows in Nottoria village (Perugia, Central Italy), in2012 and 2015. The main causes of the events have been attributed to intense rainfalls involving valleys location at the outcrop of intensely fractured limestones. In situ surveys and satellite images also revealed vegetation cutting,occurred in the area between 2005 and 2011.
An experimental in situ and laboratory investigation is ongoing to assessthe role of vegetation cutting on the triggeringof the debris flows. The debris material consists of calcareous pebbles of varying sizes diffused in a marly-clayey matrix.
In the paper, the results of conventional direct shear tests on dry and fully saturated samples and in-situ corkscrew measurements are presented and discussed. Starting from dry condition, wetting paths were performed upon shearing, showing an abrupt reduction of volume (collapse upon wetting) together with a sharp shear stress reduction, moving towards fully saturated conditions. The hydro-mechanical properties of the material were also investigated when in partially saturation condition.

Keywords: Vegetation cutting, Debris flow, Root properties, Unsaturated soil conditions.