Geomorphological features and temporal distribution of the present day landslides activity in the Gordana Basin (Zeri, Northern Apennines): a dendrogeomorphological analysis

Abstract

Patigno Village (Zeri, Northern Apennines) is build on a slope widely involved in a large landslide. The superficial part of the slope is reactivated by an high number of landslides which damaged either villages and roads. Looking for understand the dynamic of these sliding movements a survey have been made taking in account those that can be considered as active. Two of them are located in Ternesia site and six others on the toe of Patigno slope. Dendrogeomorphology has been the main analysis technique. That allowed to reconstruct either the temporal and spatial evolution of landslides, looking at effects recorded by trees involved in the movements. Trees belonging to Quercus cerris L. species have been sampled by using an increment borer, leading to a total amount of 251 cores collected. Their analysis allowed to date trees and abrupt growth changes, which are linked with effects inducted by landslides. Development of master plot has shown some event years for the slope. On Ternesia site, activity phases have been pointed out during the years 1957, 1961-62, 1974-76, 1981-83, 1993; along the toe of the Patigno slope the main phases can be referred to the years 1970-72, 1974-75, 1982-83, 1993. By drawing event-response maps has been possible to reconstruct the spatial evolution of sliding movements in Ternesia site. This pointed out as the increasing of the displaced mass was mainly due to a retrogressive distribution of activities.