BANK EROSION AND INSTABILITY MONITORING WITH A LOW COST TERRESTRIAL LASER SCANNER

ABSTRACT: Among the dominant processes taking place in a river basin, especially mountain ones, sediments creation and transport play a key role in morphological processes. Studies usually focus on big mass movements, such as landslides and debris flows, or on wide spread slope erosion due to rainfalls, while bank erosion is neglected or not considered essential for sediment budget at basin scale. Nevertheless, authors consider bank erosion a process that deserve more careful studies; not only the sediment share from bank erosion is not negligible in steep mountain rivers, but also the process can threat structures on river sides due the possibility to have limited, but still significant, mass collapse of bank sections during intense events. The paper present an attempt to monitor bank erosion in a section of a river in Northern Italy Alps and to put it in relation with weather and water discharge. Survey campaign was set up at regular time intervals, or after particularly intense rainfalls, and uses a Terrestrial Laser Scanner (TLS) to acquire the bank surface. The tool was developed internally, at Politecnico di Milano, to meet requirements about low cost level and good accuracy. Successive acquisitions of point clouds were elaborated, via an ad-hoc MatLab code, to determine erosion, or deposition, volumes of sediments. These volumetric results have been evaluated in relation with rainfalls and freeze-thaw cycles looking for a relationship between environmental conditions and bank failures. Some interesting results are shown, such as a relation between erosion rates and temperature or water flow in the river. The path to a complete process understanding and modelling is long, however the results reported can be considered a first step towards objective

Affect's Effects: Considering Art-activism and the 2001 Crisis in Argentina

Anxious of straying too far from traditional rational actor models and an assiduous positivism, social movement scholars have displayed a persistent tendency to overlook the specificities of visual tools and aesthetic experience in claim-making and political protest. Often, as a direct consequence, the possibilities for mobilization and the matrices within which action takes place are described and understood in ways that are oversimplified, even distorted. Notably, small steps have been taken to overcome these distortions by building in a theory of affect that reserves a crucial space for the extra-discursive in the study of contentious politics. Extending some of these insights, this article reveals how an affect-informed approach can be particularly illuminating in studies of art-activism. It takes stencil protests from the aftermath of the 2001 crisis in Argentina as a case in point, discussing affects and their effects on porteño street artists. In so doing, it strengthens the case for greater incorporation of affect as a tool for understanding in literatures that deal with questions of framing, art-activism and the possibilities for social change

Phenotypical and Functional Characterization of Mesenchymal Stem Cells Derived From Patients Affected by Schwachman-Diamond Syndrome

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Long-term hydrogeophysical monitoring of the internal conditions of river levees

To evaluate the vulnerability of the earthen levee of an irrigation canal in San Giacomo delle Segnate, Italy, a customized electrical resistivity tomography (ERT) monitoring system was installed in September 2015 and has been continuously operating since then. Thanks to a meteorological station deployed at the study site, we could investigate the relationship between the inverted resistivity values and different parameters, namely air temperature, rainfall and water level in the canal. Air temperature seems to have a minor but not negligible influence on resistivity variations, especially at shallow depth. A model of soil temperature versus depth was used to correct resistivity sections for air temperature variations through the different seasons. Changes of the water level in the canal and rainfall significantly affect measured resistivity values. At the study site, the most important variations of resistivity are related to saturation and dewatering processes in the irrigation periods. Although we explored the effect of drawdown procedures on resistivity data, this process, causing rapid variations of resistivity values, is still not completely understood because the canal is rapidly emptied during rainfall events. Therefore, the effect of variations of the water level in the canal on levee resistivity cannot be distinguished from the effect of rainfalls. To study the effect of water level variations alone, we considered the beginning of the irrigation period when the dry canal is gradually filled and we observed a smooth trend of resistivity changes. The effect of rainfall on the data was studied during different periods of the year and at different depths of the levee so that the resistivity variations could be evaluated under different conditions. To convert the inverted resistivity sections into water content maps, an empirical and site-dependent relationship between resistivity and water content was obtained using core samples. Water content data can then be used for the implementation of stability analysis using custom modeling. This study introduces an efficient technique to monitor earthen levees and to control the evolution of seepage and water saturation in pseudo-real time. Such a technique can be exploited by Public Administrations to reduce hydrogeological risks significantly

SUSCEPTIBILITY MAPPING OF SHALLOW LANDSLIDES INDUCING DEBRIS FLOWS: A COMPARISON OF PHYSICS-BASED APPROACHES

The assessment of timing and potential locations of rainfallinduced shallow landslides through mathematical models represents a challenge for the assessment of landslide hazard, especially in cases with limited or not available data. In fact, modeling slope hydrological response and stability requires accurate estimates of unsaturated/saturated hydraulic and geotechnical properties of materials involved in landsliding, as well as climate and topography. Such aspect is relevant for the prediction of location and timing of landslide events, which is greatly needed to reduce their catastrophic effects in terms of economic losses and casualties. To such a scope, we present the comparison of results of two physics-based models applied to the assessment of susceptibility to shallow rainfall-induced landslides in Valtellina region (northern Italy). The analyses were carried out considering effects of availability, resolution and type of data concerning spatial distribution, thickness and properties of soils coverings. For such a scope, the Transient Rainfall Infiltration and Grid-Based Regional Slope-Stability (TRIGRS) and the Climatic Rainfall Hydrogeological Modeling Experiment (CHRyME) models were considered. The study emphasizes issues in performing distributed numerical slope stability modeling depending on the availability of spatially distributed soil properties which hamper the quality of physic-based models. Further analyses aimed at the probabilistic assessment of landslide spatial distribution, related to a specific value of rainfall threshold, can be considered as potentially applicable to multi-scale landslide hazard mapping and extendable to other similar mountainous frameworks

INTEGRATED ANALYSIS OF TRIGGERING AND RUNOUT SUSCEPTIBILITY TO LANDSLIDE-INDUCED DEBRIS FLOWS IN ALPINE CATCHMENTS

In the last decades the Valtellina valley (northern Italy) has suffered from several catastrophic rainfall-induced shallow landslide events inducing debris flows. The growing of urban settlements has driven population to colonize areas at risk, where prediction and prevention actions are nowadays a challenge for geoscientists. Debris flows are widespread in mountain areas because occurring along steep slopes covered by loose regolith or soil coverings. Under such conditions, heavy rainfall events might cause slope instabilities due to the increase in pore water pressure depending on hydraulic and geotechnical properties as well as thicknesses of soil covers. Despite the initial small volumes, debris flows hazard is significant due to the sediment entrainment and volume increase of the involved material, high velocity and runout distance. In such a framework, predicting timing and position of slope instabilities as well as paths, volumes, and velocity of potential debris flows is of great significance to assess areas at risk and to settle appropriate countermeasures. In this work, back analyses of debris flows occurred in representative sites of the Valtellina valley were carried out with the aim of understanding their features and providing a methodological basis for slope to valley scale susceptibility mapping. Numerical modeling of slope stability and runout was completed allowing the identification of the detachment, transport, and deposition zones of previously occurred landslides, including other potentially unstable ones. Results from this study emphasize issues in performing distributed numerical modeling depending on the availability of spatially distributed soil properties which hamper the quality of physics-based models. In the framework of hazard mapping and risk strategy assessments, the approach presented can be used to evaluate the possible runout phase of new potential debris flows recognized by geomorphological evidence and numerical modeling. Furthermore, analyses aimed to the probabilistic assessment of landslide spatial distribution, related to a specific value of rainfall threshold, can be considered as potentially applicable to multi-scale landslide hazard mapping and extendable to other similar mountainous frameworks. © (2024), (Sapienza Universita Editrice). All rights reserved

Design and Tests of the Silicon Sensors for the ZEUS Micro Vertex Detector

To fully exploit the HERA-II upgrade,the ZEUS experiment has installed a Micro Vertex Detector (MVD) using n-type, single-sided, silicon micro-strip sensors with capacitive charge division. The sensors have a readout pitch of 120 micrometers, with five intermediate strips (20 micrometer strip pitch). The designs of the silicon sensors and of the test structures used to verify the technological parameters, are presented. Results on the electrical measurements are discussed. A total of 1123 sensors with three different geometries have been produced by Hamamatsu Photonics K.K. Irradiation tests with reactor neutrons and Co-60 photons have been performed for a small sample of sensors. The results on neutron irradiation (with a fluence of 1 x 10^{13} 1 MeV equivalent neutrons / cm^2) are well described by empirical formulae for bulk damage. The Co-60 photons (with doses up to 2.9 kGy) show the presence of generation currents in the SiO_2-Si interface, a large shift of the flatband voltage and a decrease of the hole mobility.Comment: 33 pages, 25 figures, 3 tables, accepted for publication in NIM

Geoelectrical characterization and monitoring of slopes on a rainfall-triggered landslide simulator

In this paper, we present the results of time-lapse electrical resistivity tomography (ERT) monitoring of rainfall-triggered shallow landslides reproduced on a laboratory-scale physical model. The main objective of our experiments was to monitor rainwater infiltration through landslide body in order to improve our understanding of the precursors of failure. Time-domain reflectometry (TDR) data were also acquired to obtain the volumetric water content. Knowing the porosity, water saturation was calculated from the volumetric water content and we could calibrate Archie's equation to calculate water saturation maps from inverted resistivity values. Time-lapse ERT images proved to be effective in monitoring the hydrogeological conditions of the slope as well as in detecting the development of fracture zones before collapse. We performed eight laboratory tests and the results show that the landslide body becomes unstable at zones where the water saturation exceeds 45%. It was also observed that instability could occur at the boundaries between areas with different water saturations. Our study shows that time-lapse ERT technique can be employed to monitor the hydrogeological conditions of landslide bodies and the monitoring strategy could be extended to field-scale applications in areas prone to the development of shallow landslides