From site-scale to large areas monitoring of ground deformation phenomena by integration of different DInSAR techniques in Crotone Province (Southern Italy)

One of the most significant aims of this research project has been to apply SAR methods for the monitoring, the investigation and the evaluation of ground deformation phenomena in the Crotone province (Southern Italy). In detail, landslides and subsidence are the most remarkable and dangerous natural hazards in the study area, affecting people, buildings and main infrastructures. The intention was to show the potential of Differential Interferometry SAR (DInSAR) techniques for the detection and the estimation of the velocities and of the deformation of surface displacements, both on very local scale (slope scale) and on wide areas (kilometre-size extension). Such aim is achievable through the integration of DInSAR techniques along with conventional monitoring tools. The general idea of the project has been to assess the landslide hazard in selected areas of the Crotone province and to update the related landslide inventory map of the area, dated back to 2006, by means of DInSAR techniques. These goals have been reached through the comprehension and the understanding of the movements, on one hand on a very local scale (slope), and on the other hand, on a wide-area scale (the whole Crotone province). Additionally, two other case studies of subsidence, originated by different sources, have been studied with interferometry techniques, showing the suitability of such methods for other types of ground deformation. Several Multi Temporal Interferometry (MTI, Wasowski & Bovenga, 2014) approaches have been here applied, in order to investigate and analyze displacements present in the area, and the integration with “conventional” methods, such as inclinometers, piezometers and geomorphological surveys, turned out to be relevant for these purposes, providing very precise information about the nature and causes of ground deformation

A modified tank model including snowmelt and infiltration time lags for deep-seated landslides in alpine environments (Aggenalm, Germany)

Deep-seated landslides are an important and widespread natural hazard within alpine regions and can have significant impacts on infrastructure. Pore water pressure plays an important role in determining the stability of hydrologically triggered deep-seated landslides. Based on a simple tank model structure, we improve groundwater level prediction by introducing time lags associated with groundwater supply caused by snow accumulation, snowmelt and infiltration in deep-seated landslides. In this study, we demonstrate an equivalent infiltration calculation to improve the estimation of time lags using a modified tank model to calculate regional groundwater levels. Applied to the deep-seated Aggenalm landslide in the German Alps at 1000–1200&thinsp;m&thinsp;a. s. l. , our results predict daily changes in pore water pressure ranging from −1 to 1.6 kPa, depending on daily rainfall and snowmelt, which are compared to piezometric measurements in boreholes. The inclusion of time lags improves the results of standard tank models by  ∼ &thinsp;36 % (linear correlation with measurement) after heavy rainfall and by  ∼&thinsp;82 % following snowmelt in a 1–2-day period. For the modified tank model, we introduced a representation of snow accumulation and snowmelt based on a temperature index and an equivalent infiltration method, i.e. the melted snow-water equivalent. The modified tank model compares well to borehole-derived water pressures. Changes of pore water pressure can be modelled with 0–8 % relative error in rainfall season (standard tank model: 2–16 % relative error) and with 0–7 % relative error in snowmelt season (standard tank model: 2–45 % relative error). Here we demonstrate a modified tank model for deep-seated landslides which includes snow accumulation, snowmelt and infiltration effects and can effectively predict changes in pore water pressure in alpine environments.</p