Investigation on the Role of Water for the Stability of Shallow Landslides—Insights from Experimental Tests

Abstract

Shallow soil slips are a significant hydrogeological hazard which could affect extended areas of the high-gradient mountainous landscape. Their triggering is highly dependent on the rainfall water infiltration and its further redistribution, as well as the characteristic properties of the soil itself. The complex interaction between those factors generates a considerable degree of uncertainty in the understanding of the governing processes. In this work, we take a small step further towards the untangling of those intricate relationships through observation. The results of a set of 20 downscaled shallow land mass failures are analysed through a principal component analysis and a further detailed look at the resulting parametric trends. Moreover, electrical resistivity tomography measurements are added up to the interpretation of experimental data, by providing a glimpse on the rainfall water infiltration process at the subsurface level. The outcome of this work implies that the coupled interaction between rainfall intensity, hydraulic conductivity and soil moisture gradient is governing the stability of soil and while rainfall intensity and duration are essential instability predictors, they must be integrated with antecedent moisture and site-specific characteristics. A tentative comparison of the dataset with existing rainfall thresholds for shallow landslide occurrence suggests the potential application of experimental tests for thresholds’ definition or validation under the appropriate dimensional analysis. A dimensional analysis indicated the interconnection of parameters intrinsic to the problem, and the significance of scale effects in performing a downscaled simulation of land mass failure.