Sabrina Bonetto

A tool for semi-automatic linear feature detection based on DTM

Abstract The tectonic movement along faults is often reflected by geomorphological features such as linear valleys, ridgelines and slope-breaks, steep slopes of uniform aspect, regional anisotropy and tilt of terrain. In the last years, remote sensing data have been used as a source of information for the detection of tectonic structures. In this paper, a new fully 3D approach for semi-automatic extraction and characterization of geological lineaments is presented: linear features are detected on a DTM by means of algorithms based on principal curvature values, and then they are grouped according to data collected from literature review regarding expected orientation of lineaments in the studied area. The overall positive aspects of this semi-automatic process were found to be the informativeness on geological structure for preliminary geological assessment and set identification, the possibility to identify the most interesting portions to be investigated and to analyze zones that are not directly accessible. This method has been applied to a geologically well-known area (the Monferrato geological domain) in order to validate the results of the software processing with remotely sensed data collected from literature review. As regard to orientation, spatial distribution and length of the lineaments, the study demonstrates a correspondence of the obtained results with both remote sensed linear features and field geostructural data.

A case study on the application of destructive and non-destructive methods for evaluating jet-grouting column integrity for bridge-pier scour protection (Cuneo, NW Italy)

A case study on the use of direct and indirect investigations for the effectiveness evaluation of jet-grouting interventions for bridge scour protection is presented. The major concern of this scour countermeasure is that a reliable verification and imaging of the exact dimensions and shape of the grouted elements and their related strength and integrity are difficult to obtain. An integrated cost-effective and slightly invasive approach, by means of indirect surveys, is proposed in this work to limit re-drilling and core sampling of jet columns. Tests are performed on a bridge located in the Province of Cuneo (NW Italy). On site, active fluvial activity was scouring four of the 19 bridge piers and jet-grouting interventions were designed to prevent bridge collapse. A dual approach was consequently applied to evaluate the goodness of jet-grouting treatments: results of direct tests (visual and mechanical characterization of core drillings, with Point Load and Uniaxial Compressive Strength tests) have been compared to indirect investigations (seismic down-hole tests and 2-D cross-hole tomography, laboratory Ultrasonic Pulse Velocity measurements). All the techniques showed potentiality in identifying variations of the jet-grouting properties within the columns. Generally, worsening in jet-grouting properties was coherently identified by a decrease in the seismic velocities and in the mechanical parameters and confirmed by visual inspection of core drillings. Local anomalies and discrepancies between the adopted method were however highlighted and critically discussed as a function of the limitations, disturbances and investigated volumes of each method.

Using Improved Varieties of Pearl Millet in Rainfed Agriculture in Response to Climate Change: A Case Study in the Tillabéri Region in Niger

The seasonal effects of global warming and water shortages begin to be observed on agricultural production and forecast trends encourage studies on adaptation to climate change. In Niger, West Africa, farmers have always had to cope with irregularity and poor distribution of rainfall. In recent years, a variation in the frequency and duration of rainy season were observed, suddenly affecting a drop in agricultural productions with the resulting food crisis. Therefore, it is necessary to find measures to adapt to the climate variability. This study focus on the Tillaberi region (Niger) where pearl millet is one of the main agricultural product. In the last few years, variations in rainfall distribution and quantity have negatively influenced the yield of the millet crops. A climatic assessment of the region has been verified collecting information from both previous studies and satellite data. Two early improved varieties of pearl millet (SOSAT-C88 and HKP) drought resistant have been distributed to local farmers in 16 pilot areas of the Tillaberi region and the crop yields were compared to those of the local traditional variety cultivated in the same area. The results have identified a significant increase in production, up to 62%, with the improved varieties compared to the local one. These results suggests the possibility of a potential extension, in this region, of improved varieties to mitigate the effects derived by climate change in the agricultural productivity in order to avoid famine and guarantee food security.

An Approach to Use Earth Observation Data as Support to Water Management Issues in the Ethiopian Rift

In several areas of the world, water distribution influences the local development. In the volcano-tectonic depressions of the Main Ethiopian Rift (MER) many perennial rivers and lakes are present and constitute an important resource for agriculture, livestock, fishery, soda abstraction, human health and local ecosystems. This paper focuses on the analysis of the temporal and spatial variations of water surface of the lakes in the central Ethiopian Rift in relations to precipitation climatology, in order to better understand the effective role of the climate in the water resources modification in respect to human factor. This should help to establish correct water management practice and implement integrated water management for the protection of lakes in reason of their impacts on the lifestyles of intended beneficiaries like farmers, fishermen, and domestic water consumers. The employed approach and integrated different satellite data (Landsat and NASA-TRMM) in order to generate a proper database for the analysis of the seasonal movements according to climatological variations.

The northernmost record of the Messinian salinity crisis (Piedmont basin, Italy)

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Integration of Geological and Geophysical Survey for a Geo-Exchange System Design

The design of a geothermal system represents a key moment since the future effective operation of the plant will strictly depend from it. A correct and effective design of a geo-exchange system should not be performed without a precise and accurate knowledge of the subsoil variability and its related thermal properties. The present work shows a case study for the design of a field of borehole heat exchangers for climate control and domestic hot water production in a newly constructed residential area located in the municipality of Tarvisio (NW Italy). It is pointed out the fundamental importance of a correct geological prospection, based on the integration of direct and indirect surveys. Correct investigations were indeed crucial, coupled to a Thermal Response Test, for a proper identification of the thermodynamic characteristics of the subsoil and then for the optimization of the system. Specifically, this case study aims to serve as an example to highlight the importance of variability in the horizontal scale of the thermal conductivity of the subsoil and the potential errors that can be made if no investigation is undertaken.

A Tool for Semi-automatic Geostructural Survey Based on DTM

Tectonic movement along faults is often reflected by characteristic geomorphological features such as linear valleys, ridgelines and slope-breaks, steep slopes of uniform aspect, regional anisotropy and tilt of terrain. In the last years, the remote sensing data has been used as a source of information for the detection of tectonic structures. In this paper, we present a new approach for semi-automatic extraction and characterization of geological lineaments. The overall positive aspects of this semi-automatic process were found to be the rapidity of preliminary assessment, the possibility to identify the most interesting portions to be investigated and to analyze zones that are not directly accessible. This method has been applied to a geologically well-known area (the Monferrato geological domain) in order to validate the results of the software processing with literature data. Results obtained are discussed and preliminary remarks are put forward.

Geological and Geophysical Tests to Model a Small Landslide in the Langhe Hills

In April 2009, North-West Italy was interested by heavy rainfalls that triggered several landslides, especially of shallow type, and caused relevant rise of water level in many rivers, in some cases even beyond the alert level. Particularly in the hills near Alba (NW Italy), many landslides occurred, most of them belonging to the debris flow or soil slip types. In this area, a small but interesting landslide involved a local road and a high quality, recently planted, vineyard. The present study shows the use of different disciplinary approaches focused to understand the behaviour of this landslide: in particular, besides geological and geomorphologic studies, detailed topographic and geophysical surveys together with an in situ geotechnical/geomechanic characterization were applied. The combined interpretation of the different techniques and of field observations allowed to define a geological and technical model of the landslide, both in surface than in depth, that clarified the triggering mechanism of the landslide and allowed to perform a back analysis on both strength and pore pressure parameters.