Characterization of the soil properties in agricultural areas affected by shallow landslides: application in Messina area (Sicily).

Abstract

The determination of soil properties is considerable challenge when it is aimed to evaluate the spatial distribution of one or more parameters across significant surfaces. In fact, terrain sampling and field data are punctual measurement; therefore, quantitative models are needed to predict the spatial distribution of soil attributes. The spatialization of field and laboratory data is a very important information in landslide studies. Raster layers displaying soil properties can be used both for statistical models and for the parameterization of physically based models. The purpose of this work is to produce a detailed hydrological and mechanical characterization of the soil affected by shallow landsliding processes. The study area is located in Messina (Southern Italy) where a debris flow event occurred on the 1st October 2009. In particular, two small and independent (2 km2) hydrological units were chosen: Racinazzi and Saponarà catchments. The sample sites were selected using a provisional predictive pedologic model based on the topographic attributes Topographic Wetness Index and Steepness of slope. The field analyses were aimed to determine soil thickness, hydraulic conductivity and other soil mechanical properties. The fieldwork was carried out using: (1) Dynamic Cone Penetrometer (2) Amoozemeter (3) Auger sampler. The laboratory analysis of the collected samples have performed in order to characterize granulometry and the Atterberg limits. Stochastic approaches have been then adopted to regionalize the punctual information for each of the collected properties resulting in robust spatial distributions used to characterize landslide prone conditions. The results show the slope instability mainly affect the terraced areas characterized by the presence of a thin layer of soil which, according to the laboratory analysis, testifies an incomplete pedogenesis.