28 research outputs found
Shallow landslides susceptibility assessment by means of remotely sensed data and field survey: multi-scale analysis/monitoring of predisposing factors in a climate change context
No full textThe role of land use changes in the distribution of shallow landslides
No full textThe role of land use dynamics on shallow landslide susceptibility remains an unresolved problem. Thus, this work aims
to assess the influence of land use changes on shallow landslide susceptibility.
Three shallow landslide-prone areas that are representative of peculiar land use settings in the Oltrepò Pavese
(North Apennines) are analysed: the Rio Frate, Versa and Alta Val Tidone catchments. These areas were affected
by widespread land abandonment and modifications in agricultural practices from 1954 to 2012 and relevant
shallow landslide phenomena in 2009, 2013 and 2014.
A multi-temporal land use change analysis allows us to evaluate the degree of transformation in the three investigated
areas and the influence of these changes on the susceptibility to shallow landslides.
The results show that the three catchments were characterised by pronounced land abandonment and important
changes in agricultural practices. In particular, abandoned cultivated lands that gradually recovered through natural
grasses, shrubs and woods were identified as the land use change classes that were most prone to shallow
landslides.
Additionally, the negative qualities of the agricultural maintenance practices increased the surface water runoff and
consequently intensified erosion processes and instability phenomena.
Although the land use was identified as the most important predisposing factor in all the study areas, some cases
existed in which the predisposition of certain areas to shallow landslides was influenced by the combined effect
of land use changes and the geological conditions, as highlighted by the high susceptibility of slopes that are
characterised by adverse local geological (thick soils derived from clayey-marly bedrocks) and geomorphological
(slope angle higher than 25°) conditions
The role of the vineyards on slope stability: a case study from an area susceptible to shallow landslides
No full textHilly slopes cultivated with vineyards of Oltrepò Pavese (northern Italy) are often affected by rainfall-induced shallow landslides, which cause destruction and loss of the cultivations. The assessment of soil reinforcement of grapevine roots is then fundamental for slope stability analyses. In sites affected by shallow landslides, root density is lower, probably due to the lowest soil permeability. Despite the differences of soil features, type of bedrock, grapevine age and vineyards row orientation, an unique relationship between root diameter and root tensile strength can be identified. The total root reinforcement follows the trend of the root density. Grapevine roots can give a good reinforcement on soil, usually in the first 0.9-1.0 m from ground level
Evaluating Liquefaction Potential of Soils Using CPT: A Case Study in the Central Po River Plain, Italy
No full textThe role of human activities on sediment connectivity of shallow landslides
No full textSediment connectivity within a catchment depends largely on the morphological complexity of the catchment
and is strictly related to the anthropogenic modification of the landscape.
In this context, the present research evaluates the role of anthropogenic effects on landscape modifications
and the resulting influence on sediment delivery. An assessment of sediment connectivity was carried out for
three different human impact scenarios: (i) drainage system density reduction, (ii) road network variation and
(iii) land use changes. In addition, shallow landslides were used as sediment source areas to evaluate the potential
connection between these sediment sources and downstream areas (e.g. main channels and road network).
Two small catchments in the Oltrepò Pavese area (Northern Apennines, Italy), with different size and morphological
setting, were analysed: the Rio Frate (1.9 km2) and the Versa (38 km2) catchments. In both areas,
several shallow landslides were triggered in 2009 (Rio Frate and Versa) and in 2013 (Versa).
Results highlight the role of the landscape complexity in coupling/decoupling upstream sediment sources,
such as shallow landslides, from the main channel network and roads.
In addition, the analysis identified instability phenomena characterized by high connectivity values, allowing
determination of the areas in which mobilized sediment could potentially damage important infrastructures such
as the road network or contribute to flooding induced by aggradation or obstruction of the river bed.
The proposed approach provides a methodological framework to help improve watershed and land management
strategies, especially in shallow landslides prone-areas
Evaluation of anthropogenic effects on the sediment delivery dynamics in response to slope instability
No full textIn this work a sediment connectivity assessment was performed in order to evaluate the role of anthropogenic effects on the sediment delivery dynamic, in response to slope instability. In particular, the potential connection of sediment source areas with the main channel networks and roads was investigated. Two catchments with different size and morphological setting were analysed: the Rio Frate and Versa catchments (Oltrepo Pavese, Northern Apennines, Italy). The two areas were affected by important anthropogenic effects, such as land use changes, drainage system and road network modifications. Moreover, several shallow landslides occurred in these areas in 2009 and 2013. The performed analysis allowed to obtain maps of sediment connectivity according to the main landscape modification due to human activities. In particular, the effects of these modifications on the degree of connectivity between shallow landslides, roads and streams, were investigated. In addition, the instability phenomena characterised by the highest connectivity were determined, allowing the determination of the areas where the mobilized sediment from shallow landslides can potentially reach roads and stream network, causing potentially extensive damages
Understanding the relationship between sediment connectivity and the spatio-temporal landscape changes in two small catchments.
No full textUnderstanding relationships between morphology and ecosystem structure in a shallow tidal basins of Venice lagoon
No full textCoastal wetlands represent complex ecosystems prone to continue fluctuation of their internal equilibrium. They
are valuable natural resources characterized by the continue interactions between geomorphological and biological
components. Their adaptation to changing conditions is highly dependent on the rate and extent of spatial and
temporal processes and their responses are still poorly understood. According to this, the vulnerability assessment
to natural and human made hazard have became fundamental to analyse the resilience of these areas, their ability
to cope with the impacts from externally driven forces or the efforts needed to minimize the impacts (Gitay et al.,
2011). The objective of this research is to develop a comprehensive and replicable method through the application
of Multi-Source data analysis, based on the integration of Earth Observation data and field survey, to analyse a
shallow tidal basin of salt marshes, located in the northern part of the Venice lagoon. The study site is charac-
terised by relatively elevated areas colonized by halophytic vegetation, and tidal flats, with not vegetated areas,
characterized by lower elevations. Sub-pixel processing techniques (Spectral Mixing Analysis – SMA) were used
to analyse the spatial distribution of both vegetation and sediments typology. Furthermore the classifications were
assayed in terms of spatial (Power law) and temporal (Empirical Orthogonal Functions) patterns, in order to find
the main characteristics of the aforementioned spatial trends and their variation over time. The principal aim is
to study the spatio-temporal evolution of this coastal wetland area, in order to indentify tipping points, namely
thresholds, beyond which the system reaches critical state and the main climatic, hydrodynamic and morphologi-
cal variables that may influence and increase this behaviour. This research represents a new approach to study the
geomorphological processes and to improve the management and conservation planning for coastal areas
Integrating remote sensing and GIS techniques for monitoring and modeling shoreline evolution to support coastal risk management
No full textThe precise delineation of coastal areas subject to past, present, and future erosive processes plays a fundamental role in coastal risk management. Within this framework, satellite data represent a valuable synoptic and multi-temporal information source. Therefore, this research integrated remote sensing and GIS techniques for mapping and modeling shoreline evolution through time. Long-term shoreline's proxy rates of advance and retreat were determined using Landsat data from the mid-1980s to 2011 and subsequently, a short-term scenario (3 years) was predicted and validated. Two different coastal environments, Oceanic and Mediterranean, were investigated. In the first, different proxies were analyzed, thereby enabling a multi-proxy analysis. Findings showed that the method provided more accurate results in higher energy environments (Oceanic) and where the coastline is not urbanized. Results also highlighted the importance of performing multi-proxy analyses in given study areas, to more reliably define shoreline modeling. Importantly, during the analyses, particular attention was given to assessing uncertainty, which is crucial when outcomes of scientific research are considered for management
Differences between mechanical and electrical cone penetration test in the liquefaction hazard assessment and soil profile reconstruction
No full textLiquefaction - hazard assessment is often accomplished by means of simplified procedures, which are based on CPT. The CPT liquefaction procedures, generally, require cone penetration test with electrical tip or the measure of u (CPTu); however, in most countries, as Italy, penetrometric tests are carried out with mechanical tip (CPTm). Generally, CPTm leads to an estimate of the Liquefaction Potential lower than that inferred from CPTu. Moreover, CPTm has a reduced resolution in soil profiling. While the cone – shape effects on qc are not very relevant, those on fs can strongly influence the FSL calculation, especially in the case of silty sands. Within this framework, the main aim of this work is to identify the differences in liquefaction - hazard evaluation and soil profile interpretation in pairs of CPTm/CPTu. After that, two methodologies were used to correct CPTm results. At first, it was developed an empirical correlation between the sleeve friction measured with CPTm and that measured with electrical CPT/CPTu. After that, a method developed in literature was applied to the same CPTm/CPTu pairs. The two corrections were compared in order to see which one led to the best results in terms of enhancement of the liquefaction hazard assessment and soil profile reconstruction. Tests have been carried out in the area interested by the 2012 Emilia earthquake (Italy)
