Search

From the 11th to the 16th of July 2022, a Summer School on "Landslides and Slope Stability Analysis in Rwanda" took place at Rwanda Polytechnic – College of Musanze (Rwanda). The Summer School was organized by the hosting institution (Rwanda Polytechnic – College of Musanze) in cooperation with the University of Parma (Italy), Rwanda Water Resources Board (RWB), and Rwanda Transport Development Agency (RTDA) in the framework of the Erasmus + EnRHEd project (https://enrhed-erasmusplus.com/). The EnRHEd project ("Enhancement of Rwandan Higher Education in strategic fields for sustainable growth") is co-funded by the European Commission and is coordinated by the University of Parma. Among the strategic fields for sustainable development, this project deals with "Environmental protection, safety, and management." In this domain, the topic of landslides plays a fundamental role, especially referring to the Rwandan context. It was the first time such a kind of Summer School on slope stability analysis took place in Rwanda. Besides the organizing institutions, the Summer School was supported by many other sponsors, like ICL – International Consortium on Landslides, AIGeo – Italian Association of Physical Geography and Geomorphology, IAH Italian Chapter – International Association of Hydrogeologists, Rocscience Inc., and the University of Parma. [ABSTRACT FROM AUTHOR]

Geomorphological mapping can be described as a group of techniques employed to systematically record the morphology of the ground, landforms, landscape-forming processes and materials that constitute the surface of the Earth (Griffiths et al., [13]; Lee, [16]). In the paper by [10], the "geo-historical" map is described as a synthesis of historical and geomorphological data for landslides and landslide occurrence in the Ceno Torrent valley (Northern Apennines, Italy). The knowledge of flood-induced ground effects and flood-water dynamics is underlined as a crucial issue for hydro-geomorphic hazard assessment and mapping. This special issue presents contributions about the methodologies and tools for representing and mapping geomorphological hazards, with a focus upon hazard and risk classification and tools for land planning, risk reduction and mitigation. [Extracted from the article]

[Display omitted] • Spatial patterns of landslide events in the N-Apennines chain during the Holocene. • Lower Holocene: landslide events towards the chain interior; Upper Holocene: outwards. • Middle Holocene: most of the landslide events in a 8.5 km belt in the chain interior. • Landslide events reflect changes in atmospheric circulation pattern in the Holocene. • Lithologies and topography for locating landslides with old-dating organic remnants. In this work we examine the spatial and temporal distribution of radiocarbon dates from landslides on the NE-facing side of the Northern Apennines during the Holocene, focusing on the region's associated vegetation and climatic changes. We also propose a method for identifying areas and landslides that may contain very old organic materials for future research in the region. This analysis was based on a principal component analysis (PCA) on 5255 grid cells measuring 1 km2 each, overlaid on the study area. These grid cells incorporated variables derived from the terrain characteristics, including underlying lithologies and topographic features. Our findings reveal that, during the upper Holocene, the last dated events of recurrent and single-event landslides occurred first closer to the coldest and wettest territories once occupied by the glacier termina during the Last Glacial Maximum (LGMgt). Subsequently the last dated events occurred at distances greater than 30 km from the LGMgt, towards the mountain chain's margin. Conversely, at the beginning of the Holocene, an opposite pattern emerged, with landslide events occurring towards the chain interior. These spatial patterns were consistently observed when considering also the entire dataset of 87 dates for landslide events. During the middle Holocene, we observed that the recurrent landslides were primarily concentrated within a narrow belt 8.5 km from the LGMgt. Furthermore, higher rates of landslide activity were associated with the 4.2 ka BP event and persisted until approximately 2.0 ka BP, indicating a correlation with wet and cool periods. In conclusion, these spatial patterns in landslide events can be linked to changes in precipitation patterns and dominant atmospheric circulation in the mountain belt occurred since the beginning of the Holocene. [ABSTRACT FROM AUTHOR]

This paper investigates the role played by geomorphological and tectonic processes affecting a portion of an active mountain belt in causing the occurrence of different types of landslides developed in flysch bedrock. The adopted multidisciplinary approach (geomorphology, geology and geophysics) allowed to recognize in a portion of the Northern Apennines of Italy different types of landslides that developed in response to slope dynamics, in turn dependent on broader regional-scale tectonic processes. Sedimentary bed attitude, local tectonic discontinuities and lithology only partially influenced the type of landslides, which have been deeply affected by the activity of regional-scale antiform that controlled the hillslope geomorphic evolution in different ways. The growth of this structure and the tilting of its forelimb produced gently dipping slopes that approached the threshold angle that can cause the occurrence of (mainly) translational rockslides. Conversely, high-angle normal faulting parallel to the antiform axis (related to a later stage of activity of the antiform itself) strongly controlled the stream network evolution and caused the watercourses to deeply incise portions of their valleys. This incision produced younger steep valley slopes and caused the development of complex landslides (roto-translational slides-earth/debris flow). The results of the integrated study presented in this paper allowed to distinguish two main types of landslides whose development reflects the events that led to the geomorphological and geological evolution of the area. In this perspective, within the study area, landslides can be regarded and used as indicators of broader-scale recent tectonic processes. [ABSTRACT FROM AUTHOR]

New sedimentological sea-level indicators are presented from the River Magra coastal plain, in NW Italy. Chronologically well-constrained paralic peats and organic sediments which had been deposited in a defined relationship with sea level were recovered in four of the seven boreholes considered in this work. Their evolution scatters in the time span of the past 6000 years. Since the cores are located within a single sedimentary basin, it was possible to correct the elevation of marker horizons for the effect of sediment compaction by means of both a field and a geotechnical method. Thus, seven reliable index points for the mid- to late-Holocene sea-level rise were obtained. The age-depth model derived from them was compared with that of sea-level predictions from two different Glacial Isostatic Adjustment (GIA) models available for the area. In both cases, the modelled sea-level estimates overlie the index points, suggesting lower relative sea-level elevation than the one predicted considering the combined eustatic and hydro-isostatic components. Based on the general tectonic setting of the area, this finding was interpreted as the effect of a tectonic subsidence of the basin, the rate of which can be quantified on average as 0.5 mm/yr since the middle Holocene, with a sharp increase after 2500 yr BP. By providing a reliable estimate of the rate of tectonic subsidence in a coastal area of NW Italy, this research contributes to refining the geodynamic model of this part of the Mediterranean basin. [ABSTRACT FROM AUTHOR]

This paper presents a geomorphologic map of the Mt. Prinzera ultramafic rock complex (Parma Province, Emilia-Romagna Region, Italy) mapped at large scale (1:2500). The map is the first contribution to the detailed geomorphologic knowledge of the area within the framework of a multidisciplinary approach used to analyse Mt. Prinzera as a hard rock aquifer case study. The geomorphologic mapping was carried out by field survey and aerial photograph analysis. All the surface processes and landforms were considered, with particular attention to structural geomorphologic features. The mapping of linear morphologic features was considered useful for revealing the presence of sets of joints otherwise difficult to detect due to surface weathering. Sets of rock discontinuities are important for water seepage and percolation and their identification is crucial for developing the hydrogeological conceptual model of the aquifer. [ABSTRACT FROM PUBLISHER]

The causes of landslides generally invoked in the Northern Apennines of Italy do not fully explain some observed oriented distributions of large landslides along regional-scale tectonic structures (late orogenic antiforms). The aim of the work is to deeply explore the role of tectonics in controlling the development and arrangement of large landslides. We employed a multidisciplinary approach which took into account geomorphological and geological field data, topographic analysis and deep seismic reflection profiles integrated with previously published apatite fission track cooling ages, shallow geophysical and GPS data. In order to explore these relationships, the Valmozzola area was selected as suitable case study, owing to the presence of clearly expressed relationships between recent extensional faults and related fractures and elements of active landslides. Moreover, in the Valmozzola area contractional tectonics acted to produce rock uplift and thus topographic growth. These processes caused hillslopes to approach their threshold angle, and promoted landslides triggered mainly by climate factors. The geological and geomorphological features characterizing the Valmozzola case study affect the entire study area, as they evolved during the same tectonic and climatic phases that characterized this part of the Northern Apennines. Therefore, the results from the Valmozzola area act as a proxy to constrain the control exerted by tectonics on large landslides across a wider area. The distribution of the large landslides has been controlled by tectonics which determined lines of weakness and failure surfaces (passive role) affecting the slopes. On the other hand, tectonics also caused the topographic growth and over-steepening of the slopes (active role) that promoted the occurrence of large landslides. The distribution of large landslides may, therefore, highlight the existence of tectonic processes and it may be used as an indicator of regional-scale tectonic activity, once the geological and geomorphological framework is well constrained. [ABSTRACT FROM AUTHOR]

Abstract: Along the rock coasts of the Gulf of La Spezia, which are characterised by a Mediterranean microtidal environment, a limited number of small rock platforms are scattered, constrained in elevation within 5m above present-day sea level. This work deals with a number of these rock platforms, formed in different rock types (one in limestone and two in dolomite), that show differences in their morphology. This paper aims to provide a quantitative examination of why there are morphological differences between platforms in this region. To achieve this purpose, factors controlling platform morphology and the processes acting on them are investigated through a comparative analysis of rock strength. Rebound values, obtained testing rock surfaces with the Schmidt hammer, were compared between different platforms and between different sectors of the same platform. Each platform was subdivided into two parts based on visual difference in rock surface colour, characterised by differences in occurrence of weathering microforms and bioerosive agents. Rebound values in the lower part of the platforms proved to be lower than in the upper part, providing quantitative assessment of the occurrence of weathering acting to different extents in the upper and lower part of the shore platforms (weathering degraded rock strength in the lower part by about 15%). It was demonstrated that on the upper part of platforms, displaying moderate evidence of physical and biological weathering, lithology significantly influences the rock strength. On the portion of platforms closer to sea level, instead, differential exposure histories of the same rock type in the same environmental setting can yield statistically significant variations in rock strength values. Thus, it is clear that in the lower part of the investigated platforms, the degree of weathering has strong bearing on rock strength, and that variations in rock strength are not solely due to lithology. According to the results of this work, experimental values of rock strength of platforms in the study area depend both on the rock type and on physical weathering due to frequently repeated wetting and drying and bioerosion. Lithology is then an important factor controlling platform shape and weathering is an important process operating on them. [Copyright &y& Elsevier]

Abstract: The Luni Plain, which faces the northern Tyrrhenian Sea, underwent major landscape changes over the last 3000 years. The coastline shifted south and west, separating the ruins of the ancient Roman colony of Luni (founded in 177 BC) from the sea by means of a new coastal plain. The precise location of the coastline during the main settlement phase as well as during the city''s decline has never been established, although partial and qualitative scenarios have been suggested by various authors. According to these authors, an indentation of the coastline west of the city formed a major water basin, along the shores of which traces of pre-Roman settlements exist; near the city, two minor basins were present, suitable for hosting harbour structures. The city of Luni was famed for its harbour (Portus Lunae), from which the marbles quarried in the Apuan Alps, used to build many of the monuments in Rome, were delivered. The traces of its port, however, are scattered and uncertain. Newly available subsurface data are presented, associated with a revision of unpublished archaeological evidence of the ancient city topography. Progress in palaeoenvironmental reconstructions at Luni has been possible thanks to the collection and analysis of ancient and recent cores, supported by radiocarbon dates, as well as the interpretation of archaeological findings suitable as markers for sea-level recognition. The main environmental changes in the area have been refined: since a few centuries before the colony was founded, the Luni plain had been characterized by a complex architecture of swamps and marshes limited by dune ridges and fluvial sand bars. The positions of these landforms were not fixed, but shifted, mainly depending on the spatial relationship between the coastline and the river mouths. Determining the precise position of the Roman coastline is useful to constrain the area in which archaeological surveys should be concentrated in order to identify the harbour location. Moreover, some of these results have been used to infer altitude constraints on the sea-level position in Roman times: preliminary data are shown for constructing a Late Holocene local sea-level curve in the area. [Copyright &y& Elsevier]

Abstract: In the Schiantala Valley of the Maritime Alps, the relationship between a till-like body and a contiguous rock glacier has been analyzed using geomorphologic, geoelectric and ice-petrographic methodologies. DC resistivity tomographies undertaken in the till and in the rock glacier show the presence of buried massive ice and ice-rich sediments, respectively. Ice samples from a massive ice outcrop show spherical gas inclusions and equidimensional ice crystals that are randomly orientated, confirming the typical petrographic characteristics of sedimentary ice. The rock glacier formation began after a phase of glacier expansion about 2550±50 14C yr BP. Further ice advance during the Little Ice Age (LIA) overrode the rock glacier root and caused partial shrinkage of the pre-existing permafrost. Finally, during the 19th and 20th centuries, the glacial surface became totally debris covered. Geomorphological and geophysical methods combined with analyses of ice structure and fabric can effectively interpret the genesis of landforms in an environment where glaciers and permafrost interact. Ice petrography proved especially useful for differentiating ice of past glaciers versus ice formed under permafrost conditions. These two mechanisms of ice formation are common in the Maritime Alps where many sites of modern rock glaciers were formerly occupied by LIA glaciers. [Copyright &y& Elsevier]

Large earth slides and rocks lides evolving into earth flows are quite widespread in the Northern Italian Apennines. Despite being simply referred to as landslides, many of them are, in fact, large complexes of landslides. They evolved through multiple and/or successive movements, undergoing partial and/or total reactivations. The reactivation of pre-existing landslide bodies is the prevalent mechanism for the known landslide events, as the historical records and the technical reports indicate. Landslide reactivation is, indeed, a relevant topic from the perspective of risk assessment and mitigation. A multi-parameter monitoring system was installed on a large complex of landslides that underwent partial or total reactivations after heavy rainfall events, causing damages to buildings and infrastructures. Two clusters of automatic piezometers—each coupled with an inclinometer—and a time-lapse resistivity deployment were the core of the monitoring system. A weather station, collecting data from subsurface thermometers, and a water content probe completed the system. After the construction of a new geological model of the slope, this study aimed at understanding the possible mechanisms leading to the reactivation of the landslide. This goal was achieved by gaining insights into the process of rainfall infiltration into the landslide deposits, by determining the groundwater flow and evaluating the landslide displacements. The monitoring system captured the processes that took place in the landslide bodies and the bedrock in response to a rainfall event in early February 2017, which followed a dry period of eight months. The recorded data provided indications on the variation of the hydraulic head in the groundwater within the landslide and the bedrock, particularly at the sliding surfaces. The electrical conductivity of the groundwater and the resistivity of the terrain varied across the failure surfaces. In particular, a sudden increase in the electrical conductivity was related to the locations of the main sliding surfaces. The joint analysis of time-lapse resistivity, hydraulic heads, and groundwater electrical conductivity helped identify the locations of weaker levels within the landslide masses, which were confirmed by data from inclinometers. This study improved the knowledge of the hydrogeological behaviour of a complex of landslides in heterogeneous low-permeability media. Moreover, the obtained results contributed to the understanding of the role played by different portions of the landslide complex in the evolution of the movement. • Dynamics of earth slides-earth flows within a complex of landslides. • Time-varying resistivity and borehole water conductivity reveal landslide activity. • Increase in the electrical conductivity of groundwater is related to sliding surfaces. [ABSTRACT FROM AUTHOR]

A few hydrogeological studies have been carried out worldwide in peridotite aquifer systems, despite their wide distribution. The ophiolites are one of the main groundwater reservoir within the northern Apennines (Italy). This paper suggests the graphical solution to set the hydrogeological map of heterogeneous, multi-layered ophiolitic aquifers mapped on large scale (1:1600). The site investigation area is an ophiolite outcrop of the External Ligurian of the northern Apennines: the Mountain Prinzera rock complex area (44°38′30″N, 10°5′E; Parma Province, Emilia-Romagna Region). The hydrogeological characteristics of the tested aquifer system do not allow setting a hydrogeological map by applying usual graphical approaches. The hydrogeological map in such complex aquifer systems will show the classic hydrogeological data but must put in evidence above all (i) the main heterogeneities of the system, from the hydraulic point of view and (ii) the modifications of groundwater scenarios and pathways over time. The hydrogeological database of Mt Prinzera aquifer was managed in ESRI ArcGIS 10.0 software. [ABSTRACT FROM PUBLISHER]

Abstract: The Roman city of Luna founded in 177 BC (2127 BP) and located in NW Italy was famed for its port, from which the prized “marble of Carrara” was shipped. Despite decades of archaeological surveys, the exact location of this harbour is unknown to date. Progress in the palaeogeographic reconstruction of the Magra Valley coastal plain surrounding the ruins of Luna has been possible thanks to the collection and analysis of six cores, supported by radiocarbon dates and microfauna analyses. The late Holocene evolution of the Luna surroundings was reconstructed starting from the maximum Holocene transgression. The latter was identified from lagoonal sediments which are chronologically connected with the most landward position attained by the shoreline after the Last Glacial Maximum (LGM). Lagoon sediments are topped by swamp and floodplain deposits. A climate fluctuation was identified in the stratigraphic record, which correlates with the first Neoglacial cooling episode. The coastal plain underwent major landscape changes over the last three millennia. A few centuries before the colony was founded, the territory was characterized by a complex delta architecture, made of swamps and marshes limited by dune ridges and fluvial sand bars. The positions of these morphological features were not fixed; they shifted, depending on the spatial interaction between the coastline and the drainage network of the plain. In this paper, we present new data to improve our understanding of the environmental constraints determining the position and setting of the ancient harbour of Luna. We suggest that its location could be searched for in the water basin once present west of the city, at a distance of more than 0.25km. [Copyright &y& Elsevier]

Landslides inventories are crucial documents for extrapolating the spatial distribution of landslides that occurred in the past. However, the production of landslide hazards maps also needs deepening the knowledge on the temporal distribution of landslide activity. In this regard, historical maps and archive documents represent important sources of data and information on territory evolution through time and especially on landslides occurrence. Nevertheless, these kinds of data sources are rarely considered as they often must be interpreted integrating different disciplines. This work shows how historical and geomorphological data on landslides occurrence in an area of the Northern Apennines can be integrated to produce a synthesis map. This synthesis map put together analogic and digital information allowing to delineate the landscape evolution, in terms of spatial and especially temporal changes occurred in the study area representing a tool that could be useful for the landslide hazard assessment in territory management. [ABSTRACT FROM AUTHOR]

Pappalardo, M.; Cappietti, L.; Arozarena Llopis, I.; Chelli, A., and De Fabritiis, L., 2017. Development of shore platforms along the NW coast of Italy: The role of wind waves. This paper investigates whether waves are active morphologic agents capable of shaping the small shore platforms that characterize the rocky coast of NW Italy. Two study areas have been selected along this coastal tract: Calafuria (Livorno) and Lerici-Tellaro (La Spezia), located ca. 120 km apart, the first being shaped in sandstone and the second in dolomite bedrock. Propagation of waves in the nearshore has been simulated by numerical modeling. From wave model results, validated with data from an offshore wave meter buoy, it is inferred that waves break directly on the coast or very close to it at Calafuria, whereas for Lerici-Tellaro shores, waves mostly break up to 150 m seaward of the shore platform. This implies that the amount of energy delivered on the platform is much greater in the first case than in the second case. Given breaking depths and the height of breakers, maximum pressure and shear stress released at the breaking point were calculated for both areas. The results showed that wave forces released onto the shore platforms both at Calafuria and at Lerici-Tellaro never exceeded the compressive strength of the platform rocks, assessed using the Schmidt hammer test. It is concluded that, in the study area and with the present oceanographic conditions, wave forces are not directly capable of causing erosion on shore platforms. [ABSTRACT FROM AUTHOR]

Keywords:, extreme precipitation, paleoflood deposit, peat bog record, Holocene, northern Apennines, climate change, water cycle.A series of record breaking precipitation events have stricken the mountainous area of Emilia-Romagna Region (northern Apennines, Italy) over the last years. As consequence, several geomorphological processes, like widespread debris flows along the slopes and hyperconcentrated flood in the stream channels, shallow landslides and overbank flooding affected the territory, causing serious damages to man-made structures. The detailed study of these recent deposits compared with fossil peat bog and lake paleodeposits can provide useful insight to support a strong match between precipitation intensity and warm climatic phases in antecedent climatic periods, as expected by the increase air water vapour holding capacity at higher temperaturesHere we present the results of the field campaign performed in summer 2017 at Lake Moo a 0.15km2 peat bog located at an altitude of 1130m a.s.l. The chosen area has been affected, during the flooding of the upper Trebbia and Nure valleys 13-14 September 2015, by several high-density flows generated by the stream that flow into the plain. Our main assumption is that, in such a small drainage basin (area <2 km2), with favourable geologic and geomorphic characteristics implying advantageous sediment transfer into lake, high density flood can be triggered only by high precipitation intensity events (HPI) lasting a sufficient amount of time for water to infiltrate and mobilize large quantities of debris. The sedimentary succession (ca. 13 m-thick) was studied through the extraction of two cores and one trench. The facies/paleoenvironmental interpretation of the sedimentary succession, characterized by clusters of coarse-grained alluvial deposits interbedded with organic-rich silty clays and peaty layers, was achieved combining sedimentological and pollen data with pedological data and radiocarbon dating (AMS 14C). Observed depositional cycles, retrieved by Lake Moo cores and trench, were put in relation with other specific paleoclimatic proxies available in literature for the North-Apennine area. This comparison illustrate that the increase of extreme paleoflood (associated with coarse-grained deposits similar to the ones observed recently) correlates well with warm phases (at millennial scale), with a maximum activity in during the holocene thermal maximum. [ABSTRACT FROM AUTHOR]