Deep seated gravitational slope deformations (DSGSD) are widespread phenomena, recognized in different mountain ranges worldwide. The distribution of such phenomena at the scale of a mountain belt ...has rarely been systematically analysed in the past. Aim of the paper is to present and discuss an inventory map of DSGSD at the scale of the entire European Alps, in order to review existing knowledge and investigate general controls on these phenomena. The criteria adopted for their classification and distinction are presented. A total of 1033 DSGSDs, ranging in size between 0.03 and 108km2, have been mapped. The inventory has been validated against available local or regional landslide inventories at different scales and prepared by different authors using different approaches. The frequency–area relationship for the mapped features is presented. The spatial distribution of the mapped DSGSD has been quantified by discretizing the study area into regular square grids with different resolution, and analysed with respect to a variety of geological, geomorpohological and morphometric variables, and of their clustering. Discriminant, principal component and cluster analyses have been performed to define the most important controlling and predisposing factors. Results suggest that the occurrence of foliated metamorphic rocks, LGM ice thickness, local relief (and related parameters), slope size, drainage density and river stream power are the local parameters most positively correlated to DSGSD occurrence. The impact of these phenomena on slope morphology, in terms of hypsometry and slope gradient adjustment is also discussed.
•Review of deep seated gravitational slope deformation – DSGSD – at the orogen scale•Multivariate statistical analysis of main predisposing and controlling factors on DSGSD•Influence of shear zones, heterogeneities on stability and groundwater flow•State of activity and influence on mountain evolution
The 7.8 M
earthquake that struck Nepal on April 25th, 2015 triggered over 21,000 landslides over an area of more than 25,000 km
. These landslides contributed to mass wasting, partially compensating ...the tectonic uplift by the earthquake. In this paper we quantify the volume balance resulting from the 2015 earthquake uplift (or subsidence) and landslide erosion. Starting from a new complete earthquake-induced landslide inventory, we calculated landslide volume by adopting different strategies for low-mobility and high-mobility landslides, considering also the potential supply of sediments to the drainage network. The results show that the contribution of earthquake-induced landslides to erosion is about one order of magnitude smaller than the vertical coseismic displacement. We found landslide volume values, due to the 2015 Nepal earthquake, ranging between 251 (- 15/ + 16) Mm
up to 1503 (- 183/ + 210) Mm
based on the adopted method, and a volume due to coseismic vertical displacement of 2134 (± 1269) Mm
for the whole area. The volume balance of the 2015 Nepal earthquake is strongly dominated by tectonic displacement. We show that these estimates depend on several uncertainties. We identified and quantified uncertainties related to: (1) the choice of empirical volume-area scaling relationships and their parameters; (2) the completeness and quality of landslide inventory through comparison with available inventories; (3) the approach adopted for the assessment of elongated landslide volume; (4) the InSAR displacement data.
We present a general framework for probabilistic landslide hazard analysis. With respect to other quantitative hazard assessment approaches, this probabilistic landslide hazard analysis has the ...advantage to provide hazard curves and maps, and to be applicable to all typologies of landslides, if necessary accounting for both their onset and transit probability.
The method quantifies, for a given slope location, the exceedance probability of being affected by a landslide with a specific local intensity within a reference time interval, i.e. the hazard curve, under the common assumption that landslides behave as a Poisson process. Hazard maps are calculated, reducing the hazard curve to single values by choosing a fixed probability of exceedance following standards or regulation requirements. The method is based on the assessment of a landslide onset frequency, a runout frequency for long-runout landslides, and the local definition of landslide intensity, which can be expressed through different parameters, according to landslide typology. For long runout landslides, the runout and spatially-varying intensity and uncertainty are considered.
Hazard curves and maps play a fundamental role in the design and dimensioning of mitigation structures, in land planning and in the definition of risk and hazard management policies. Starting from the general framework, we apply the methodology for rockfall hazard analysis, and we test it in an area affected by the Christchurch 2011 earthquake, New Zealand, which triggered a large number of rockfalls, killing five people.
•Rigorous quantitative probabilistic landslide hazard analysis is proposed.•A conceptual distinction between magnitude and intensity is presented.•For rockfalls, intensity follows a log-normal distribution.•Hazard curves are calculated for each position, leading to hazard maps.
A comprehensive and reliable water balance of snow‐dominated alpine catchments is required for a holistic analysis of the hydrological and hydrogeological processes. A major limitation to the ...elaboration of this balance in alpine terrain is the difficulty of data acquisition as well as the limited presence of meteorological stations. Remotely sensed data can provide valuable information for the water balance assessment on a regional scale. We exploited Sentinel‐satellite data to estimate the groundwater storage for one hydrologic year in an extensive Alpine catchment located in northern Italy by means of the residual water balance approach. In particular, Evapotranspiration (ET) and Snow Water Equivalent were estimated with the combined use of Sentinel data, at a spatial resolution of 20 and 30 m, respectively. The results show that the adopted satellite‐based methods allow obtaining consistent and physically realistic values to describe the groundwater storage dynamics. In the period 2018–2020, a positive storage occurred only during the snowmelt period and the overall storage was negative, leading to a net lowering of the groundwater level in the floodplain. In addition, the influence of physiographic parameters (altitude, slope, and aspect) and seasonality on the estimates of ET and snow‐depth were investigated.
Key Points
A new methodology to quantify groundwater storage dynamics in snow‐dominated catchments by the residual water balance approach is presented
Hydrological components are estimated with a high temporal and spatial resolution by a novel approach based on synergistic use of Sentinel data
Results contribute to the understanding of hydrological processes in Alpine areas and the expected effects of climate change
Rockslides in alpine areas can reach large volumes and, owing to their position along slopes, can either undergo large and rapid evolution originating large rock avalanches or can decelerate and ...stabilize. As a consequence, in particular when located within large deep-seated deformations, this type of instability requires accurate observation and monitoring. In this paper, the case study of the La Saxe rockslide (ca. 8 × 10
6
m
3
), located within a deep-seated deformation, undergoing a major phase of acceleration in the last decade and exposing the valley bottom to a high risk, is discussed. To reach a more complete understanding of the process, in the last 3 years, an intense investigation program has been developed. Boreholes have been drilled, logged, and instrumented (open-pipe piezometers, borehole wire extensometers, inclinometric casings) to assess the landslide volume, the rate of displacement at depth, and the water pressure. Displacement monitoring has been undertaken with optical targets, a GPS network, a ground-based interferometer, and four differential multi-parametric borehole probes. A clear seasonal acceleration is observed related to snow melting periods. Deep displacements are clearly localized at specific depths. The analysis of the piezometric and snowmelt data and the calibration of a 1D block model allows the forecast of the expected displacements. To this purpose, a 1D pseudo-dynamic visco-plastic approach, based on Perzyna’s theory, has been developed. The viscous nucleus has been assumed to be bi-linear: in one case, irreversible deformations develop uniquely for positive yield function values; in a more general case, visco-plastic deformations develop even for negative values. The model has been calibrated and subsequently validated on a long temporal series of monitoring data, and it seems reliable for simulating the in situ data. A 3D simplified approach is suggested by subdividing the landslide mass into distinct interacting blocks.
This paper presents recommended methodologies for the quantitative analysis of landslide hazard, vulnerability and risk at different spatial scales (site-specific, local, regional and national), as ...well as for the verification and validation of the results. The methodologies described focus on the evaluation of the probabilities of occurrence of different landslide types with certain characteristics. Methods used to determine the spatial distribution of landslide intensity, the characterisation of the elements at risk, the assessment of the potential degree of damage and the quantification of the vulnerability of the elements at risk, and those used to perform the quantitative risk analysis are also described. The paper is intended for use by scientists and practising engineers, geologists and other landslide experts.
Landslides have been observed in different terrestrial environments and also on planets, satellites, and asteroids. Long runout landslides are strongly dependent on the initial mass position, ...material and slope path properties, topographic relief, and presence of volatiles. Therefore, landslides represent a means for the description of rock properties and environment of deposition prevailing at the time of occurrence and may assist in understanding the geological and climatological history of the planetary surfaces. Concerning Mars, previous studies have concentrated on Valles Marineris, where among the largest and longest landslides have been observed. Using different imagery, we present and analyze an original database of 3,118 Martian landslides of deposit area greater than 0.1 km2 throughout the planet between 60°N and 60°S, resulting in a data set far richer than previously done. After a distinction is made between different typologies of landslides, their position and the statistical distribution of their geometrical properties are examined. Large landslides cluster along the Noctis Labyrinthus‐Valles Marineris‐Margaritifer Terra system. Rock avalanches within craters are widespread, but no significant large landslides have been found at latitudes higher than 40°S and 46°N. The magnitude‐frequency distribution follows a power law with scaling exponent ranging between 1.02 and 1.57, for the entire data set and varies according to the geomorphological settings, the landslide typology, and mobility. A volume‐area power law relationship (exponent: 1.12–1.24) is proposed, based on the reconstruction of 222 landslide geometries, and compared to those for similar terrestrial landslides (1.39). Similarities with respect to terrestrial landslide, distribution with respect to impact craters and impact energy, and cryosphere extent are also discussed.
Plain Language Summary
Landslides are geomorphological phenomena that can strongly control the evolution of a landscape. They have been observed in different environments on planets, satellites, and asteroids. Landslides are sensitive to rock strength, slope geometry, and geological and environmental conditions and to their perturbations. Long runout landslides are characterized by exceptional runout and are dependent on the material and slope path properties, path geometry, presence of ice, water, liquefied soil, and vapor. Therefore, they can spread light over the conditions existing at a specific site or region or even a planet. Martian landslides are the best preserved in the whole solar system. We present and analyze an original database of about 3,100 Martian landslides spread throughout the whole planet. We study the position of landslide types and the statistical distribution of their geometrical properties, from which details of the rock material and the possible triggering and landslide dynamics can be inferred. Rock avalanches within craters are widespread in the planet, but no significant large landslides have been found at latitudes higher than 40°S and 46°N. Similarities with respect to terrestrial landslides, distribution with respect to impact craters and impact energy, and cryosphere extent are also discussed.
Key Points
A unique landslide inventory at planet scale is presented, introducing new landslide types, characters supporting analyses
Statistical analysis of an inventory one order magnitude larger than previous ones conveys new understanding about landslide distribution
Landslide triggering and environmental conditions are discussed and analyzed comparing to other data sets and terrestrial analogs
Rock glaciers are the most prominent permafrost-related mountain landforms. This study investigates the effects of the discharge from an intact rock glacier on the hydrological, thermal and chemical ...dynamics of a high-elevation stream in the NW Italian Alps. Despite draining only 39 % of the watershed area, the rock glacier sourced a disproportionately large amount of discharge to the stream, with the highest relative contribution to the catchment streamflow occurring in late summer - early autumn (up to 63 %). However, ice melt was estimated to be only a minor component to the discharge of the rock glacier, due to its insulating coarse debris mantle. The sedimentological characteristics and internal hydrological system of the rock glacier played a major role in its capability to store and transmit relevant amounts of groundwater, especially during the baseflow periods. Besides the hydrological influence, the cold and solute-enriched discharge from the rock glacier significantly lowered the stream water temperature (especially during warm atmospheric periods) as well as increased the concentrations of most solutes in the stream. Furthermore, in the two lobes forming the rock glacier, different internal hydrological systems and flowpaths, likely driven by different permafrost and ice content, caused contrasting hydrological and chemical behaviours. Indeed, higher hydrological contributions and significant seasonal trends in solute concentrations were found in the lobe with higher permafrost and ice content. Our results highlight the relevance of rock glaciers as water resources, despite the minor ice melt contribution, also suggesting their potential, increasing hydrological importance in the light of climate warming.
Display omitted
•Rock glacier (RG) sourced a disproportionately large amount of discharge to stream.•RG as relevant groundwater reservoir despite minor ice melt contributions•Stream temperature cooled by RG discharge, especially in warm atmospheric periods.•Solute-enriched RG discharge increased the solute concentrations in stream water.•Hydrochemical dynamics in RG lobes shaped by different hydrological systems.
The aim of this paper is to achieve a quantitative assessment of rockfall protection forest efficiency at regional scale, considering site specific forest, morphological and lithological parameters. ...At first, a semi-automatic GIS-based method, integrated with a multi-scenario 3D-rockfall model realized by using the simulation code HY-STONE, was used to map protection forests of Regione Lombardia (central Italian Alps). For each different forest type, a rockfall protective efficiency was assessed by using empirical (energy line angle) and modelling (HY-STONE) approaches. The empirical approach shows an increase of the energy line angle value from about 36° for the bare slopes to over 40° in forested slopes, with a value ranging from 37° to 44° for different forests types. The modelling approach is based on a new efficiency index EEI ranging from 0 (minimum efficiency, equal to no forest condition) to 1 (maximum efficiency): the efficiency of different forest types ranges from 0.08 to 0.98 by using average values of the controlling parameters. To modulate the efficiency in each single forest at regional scale, a set of parametric simulations was performed to evaluate the effects of controlling parameters. The parametric simulations show that block volume, slope gradient, DBH (diameter at breast height) and forest density are the most important parameters at controlling the efficiency. These parameters were used within a multiple linear regression function to associate a protection efficiency to each specific protection forest in the regional map. This allows to discriminate quantitatively the individual forests according to their actual efficiency. Most of the protection forest area (46%) shows an efficiency greater than 0.50 and only the 24% of the total covered area shows a value lower than 0.25.
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