1,720,999 research outputs found
Colata detritica del T. Bioley (15 ottobre 2000; Fenis, Valle d' Aosta). Analisi idrologica e geomorfologica
No full textMan-made Terraces: From Ancient Anthropic Landscape Modification to Value at Risk. The Example of Cinque Terre and Portofino, Italy
No full textMan-made terraces for agricultural purposes are a quite diffuse and ancient anthropogenic landscape modification in mountainous areas. The original slope alteration, obtained through a sequence of sub-vertical and sub-planar surfaces, represents a human interference with the geomorphic system, altering the original balance of geomorphological and geo-hydrological factors. Stone walls and soil formed by human activity have been artificially immobilized on the slopes and are available again to gravitative processes once in abandonment and may be subject to deep degradation in case of intense rain events. However, socio-economic conditions play often a crucial role in the abandonment of terraces, indirectly contributing to increase gully erosion and walls failure. The modification of the original slope profile, due to its regular geometry in respect to the typical more complex natural surface, is rather suitable to be detected through remote sensing, particularly LIDAR, as many authors have recently demonstrated. In the present research the attention has been focused on the assessment of terraces and of the volume of stones and soil that have been involved by human activity. The research area is among the most deeply modified by terraces in the Mediterranean area and internationally famous for this landscape anthropogenic alteration: The Cinque Terre in Italy is a National Park intensively visited by tourists all over the year. Then terraces represent an important economic asset that need to be preserved from degradation and collapse as partially occurred in 2011 after the intense rain event that caused flood, hundreds of landslides and consequently damage. During the 2011 event many terraced slopes have collapsed with significant loss of soil and stone walls: the research allowed to evaluate the lost volumes and to estimate the remaining ones in the Vernazza catchment
Analytical approach to geomorphological analysis, estimation of debris potential and hydraulic infrastructures in the Torrente Gravio basin (Susa Valley)
No full textThe study concerns the analysis of a mountain basin (Torrente Gravio, Susa Valley, Turin) from a geomorphological point of view, aimed to estimate the debris potential in order to assess suitability and current conditions of existing hydraulic infrastructures and to propose needed action. The methodological approach followed represents an example of an analysis that takes into consideration several elements: the climatic analysis, the historical research, the geomorphological analysis, the estimation of debris potential through an analytical procedure and, lastly, a critical analysis of existing and/or suggested hydraulic infrastructures based on other achieved results
The 4th October 2010 flash flood event in Genoa Sestri Ponente (Liguria, Italy)
No full textThe Mediterranean Sea and in particular the Liguria region have always been suffering from severe geohydrological events. Landform features and autumnal atmospheric circulation deeply influence the hazard in Genoa city, the capital of Liguria, crossed by many streams: heavy rainfall can trigger flash floods involving structures and infrastructures, often causing fatalities. The recent growth of events characterized by intense rainfall and floods has been amplified by the urban sprawl of flood-plain: these factors seem to be the most important causes in the increase of damage related to geo-hydrological events.
In this case, typical of the whole Genoan Metropolitan area, a severe event occurred in Sestri Ponente district on October 4th 2010: a critical rainfall, over 400 mm/6 hours, a peak of 125 mm/h, triggered shallow landslides and flash floods in the Molinassi and Chiaravagna catchments crossing Sestri Ponente, causing one fatality and damage of over 60 million euros. These watercourses show the typical features of Ligurian basins: small areas, steep slopes, proximity of watersheds to the coastline and intense urbanization of the plain. During this event, the hydrological response to rainfall was almost immediate, with times of concentration shorter than 25 minutes. The narrow plain on which Sestri Ponente rises was completely flooded
Yet another disaster flood of the Bisagno stream in Genoa (Liguria, Italy): October the 9th -10th 2014 event
No full textOn 2014, 9th October, short and heavy rainfall hit the Bisagno Valley. The Bisagno stream overflowed again and flooded the center of Genoa, causing severe economic damage and a victim. This is the fourth serious flooding of the stream in the last fifty years, which shows similarities with the previous catastrophic ones in 1970, 1992 and 2011, both because of the trigger conditions, determined by the orography of the city of Genoa, and for the weather situations marked by an anticyclonic block converging over the Liguria Gulf.
Between 06:00 a.m. on October the 9th and 12:00 a.m. on October the 10th in the Bisagno catchment were recorded some peaks of rain up to almost 140 mm/h and heaps of more than 550 mm/24hrs, which resulted in a rapid increase in the level of all streams of the Bisagno basin and subsequent flooding in the final stretch of the Bisagno stream, where the watercourse underflows covered by a long manhole for the last 1.4 kilometres.
Interventions for risk mitigation through more careful weather-hydrology monitoring in "nowcasting", the improvement of the civil protection activities, structural works on the watercourse, maintenance of the territory of the Bisagno catchment, a correct information and a timely communication to the population living in high risk areas are all urgently needed
A GIS spatial analysis model for landslide hazard mapping application in Alpine Area
No full textThis research describes an application of an existing method for evaluating landslide susceptibility in
alpine contest that may be considered a useful support in better land-use planning and risk management.
In order to perform the method and improve it creating landslide maps of probability, we investigated
the several conditioning factors that in general affected these morphological processes. Firstly, a landslide
inventory was prepared using both in-depth analysis of historical records and aero-photos (or
orthophotos) investigation. Secondarily, a set of conditioning factors which may affect slope movement
and failure (particularly lithology, geomorphology, land use, slope angle and aspect) was considered.
Then, the method involved the application of GIS techniques, specifically, spatial Data Analysis application.
The thematic maps of conditioning factors overlapping together with the support of the raster
calculator allowed the susceptibility map creation. The method was applied to the Germanasca Valley,
a small basin in the Italian Western Alps. This easy to use method allows one to individuate various
classes of susceptibility and to identify slope, lithology and geomorphology, driven by old landslide
events as the main conditioning factors. Furthermore, the individuation of area susceptible to landslides
verification is strictly related to risk and, as a consequence, this method permits specific zone to be
selected for detailed engineering geology studies in land-use planning
Geo-hydrological risk mitigation in a terraced landscape: LiDAR data analysis in the Portofino natural Park, Italy
No full textModification of steep slopes with man-made terraces is an ancient and widespread habit in many areas of the world. If the modification assures agricultural practices in mountainous areas, it results even as an important interference with the geomorphic processes: important quantities of soil and sediments are subtracted to the degradation processes and, in case of total abandonment of terraces, they result again available to erosion. Intense rain event may cause partial instability or even collapse of the anthropogenic structures, configuring terraces as an additional source of Geo-hydrological hazard. Recent events in Liguria - northern Italy, in Cinque Terre 2011 and Leivi (Chiavari) 2014, caused damages and even casualties due to the sudden collapse of terraced slopes. A crucial point in assessing the potential hazard caused by abandoned terraced slopes is identifying their real extension. LiDAR data analysis is an important assessment tool particularly in strong steepness areas due to the capability of recognizing linear regular structures.
In the present research LiDAR data analysis has been used to identify terraces in the Portofino Natural Park area (Liguria region, Italy) as one of the preliminary activities of the RECONECT European Union’s Horizon 2020 Research and Innovation Programme project. The project plans to realize nature based solutions to mitigate geohydrological risk in two pilot areas in the Portofino promontory and the recovery of terraces is one of the foreseen
actions. Mapping terraces is the first step to evaluate the potential risk associated to the possible instability processes and the interventions to be realized. Land use evolution in the area from 1800 to present have been indeed found through historical maps examination and used in conjunction with LiDAR analysis results
The 15 October, 2000 Debris flow in the Bioley torrent, Fenis, Aosta valley, Italy – damage and processes
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