F Dramis

The contribution of landslides to landscape evolution in Europe

Abstract After a review of some analytical and conceptual models of slope evolution with the intervention of mass movements, a proposal is made of a series of indicators for the quantitative description of landscape evolution in relation to mass movements. The ratio between landslide mobilisation rate and downwearing rate is proposed as a quantitative measure of the significance of mass movements in landscape evolution. A subdivision of European regions with respect to their susceptibility to landsliding as a process of landscape evolution is proposed. The role of landsliding for the evolution of landscape in some regions is described. The data presented show that landsliding may in some cases be the main contributor to landscape change.

Nature and Aims of Geomorphological Mapping

Abstract This chapter deals with types, purposes, contents and perspectives of geomorphological mapping, from the widely applied, ‘traditional’ symbol-based maps to the modern geographical information system (GIS)-based, object-oriented geomorphological mapping models, capable of providing reliable multiscale cartographic support to environmental analysis and land planning projects. In the last decades, the availability of new tools such as satellite imagery, global positioning systems, digital elevation models and GIS has induced a new, more effective approach in the acquisition, storage and display of geomorphological features. By this approach, geomorphologists can produce geomorphological models, consisting of land surface ‘objects’, organised into hierarchically arranged classes with spatially and temporally variable properties and geometric relationships. Unlike ‘traditional’ maps, object-oriented models can provide a full geometric description of landforms and near-surface deposits. Moreover, generalisation/decomposition procedures allow the translation of geomorphological objects from larger to smaller scales and vice versa. A case study of a GIS-based, object-oriented geomorphological model, in which ‘traditional’ symbol-oriented mapping is associated with grid-based/object-based analysis, is provided by the Salerno University (Italy) GeoMorphological Information System (GmIS). Some significant examples of traditional geomorphological maps and multiscale object-oriented mapping models produced at the Salerno University are presented in the annexes.

The Mai Maikden sedimentary sequence: a reference point for the environmental evolution of the Highlands of Northern Ethiopia

Abstract This paper presents a geomorphologic–stratigraphic analysis of a travertine dammed lacustrine–swampy sedimentary sequence, composed of clay, peaty layers and phytoclastic travertine sands, deeply incised by the Mai Maikden river, on the Highlands of Tigray (Northern Ethiopia). Radiocarbon datings of peaty deposits allow us to establish that the travertine dams have developed at least between 7310±90 yr B.P. and 5160±80 yr B.P. In the upper part of the sequence, palaeochannels filled with travertine and limestone coarse gravels and blocks, indicate the activation of concentrated erosion on the surrounding slopes. Later, both the travertine dam and the lacustrine–swampy deposits were buried by alluvial and colluvial sediments, still mixed with large amounts of organic matter, testifying to generalized slope erosion processes. The end of travertine deposition may be connected with a progressive reduction of vegetation cover and the subsequent decrease of CO2 in groundwater. The occurrence of the latter phenomena may be related to the onset of drier climatic conditions even though the finding of a large prehistoric settlement in the area, also indicates some influence of human impact.

Vertical movements in the Ionian margin of the Sila Massif (Calabria, Italy)

Detailed geological-geomorphological investigations, carried out in the Ionian coastal belt between the Trionto River and the Colognati River, allowed us to set up a tectonic-sedimentary model of the northern flank of the Sila Massif during Pliocene-Pleistocene times. The study area is characterised by a distinct step-like topography displaying a well-preserved flight of coastal plain (alluvial/marine) terraces, arranged in five altimetric orders (T1 to T5). The deposition of sandy-clayey marine sediments of Middle Pliocene age ( CTSL Unit ) and beach sandstones grading upward to gray silty clays, referred to the Emilian-Sicilian ( Bisciglia Unit ) on the basis of micropaleontological analysis, has been related to a phase of subsidence, likely induced by the activity of E-W trending extensional faults. The Bisciglia Unit grades westward into conglomerates, sandstones and silty-clay sediments forming part of juxtaposed and superimposed deltaic (and subordinate alluvial/beach) deposits. A phase of subaerial landscape modelling, starting from the Middle Pleistocene, marks the end of subsidence and the onset of a rapid uplift which, interacting with eustatic sea-level changes, gave rise to the five orders of terraces. The uplift rate of the whole area, inferred by correlating the terrace surfaces with the paleoclimatic curve proposed by Bintanja et alii (2005), is 0.65 ± 0.1 mm yr −1 . However, the contemporaneous occurrence of extensional fault activity in the area induced variations in the uplift rates, which actually range between 0.52 and 0.88 mm yr _1 in relation to the distance from the fault trace. These data highlight the competing role of fault activity and regional uplift in controlling vertical movements and surface topography at the local scale.

GIS Methodology to Assess Landslide Susceptibility: Application to a River Catchment of Central Italy

Abstract Please click here to download the map associated with this article. This paper illustrates a geographic information system (GIS) supported methodology for the assessment of landslide susceptibility. The methodology involves four operational steps: survey, site analysis, macroarea analysis and susceptibility analysis. The Survey includes the production (or acquisition) of a large-scale litho-technical map, a large-scale geomorphological map, a detailed inventory of past and present landslide events, and a high resolution DTM (Digital Terrain Model. Site analysis leads to the definition of discriminating parameters (commonly, lithological and morphometric conditions necessary but not sufficient to trigger a landslide of a given type) and predisposing factors (conditions that worsen slope stability but are not sufficient to trigger a landslide of a given type in the absence of discriminating parameters). The different predisposing factors are subdivided into classes, whose intervals are established by descriptive, statistical analysis of landslide inventory data. A numerical index, based on the frequency of landslide occurrence, quantifies the contribution of each class to slope instability. Macro-area analysis includes the generation of Litho-Morphometric Units (LMU) by overlaying discriminating parameters, manual drawing of LMU envelopes (macro-areas), generation of predisposing factor maps from the spatial distribution of predisposing factors, and heuristic weighting of predisposing factor indices. Susceptibility analysis includes the generation of Homogeneous Territorial Units (HTU) by overlaying macroareas and predisposing factor maps, and the application of a susceptibility function to the different HTU. The resulting values are normalized before the generation of the landslide susceptibility maps. The methodology has been applied to the Fiumicino River catchment, located in the western side of Latium Apennine (Central Italy) between 200 and 1300 m a.s.l. and developed on Late Miocene calcarenites, sandstones with clay intercalations, and marls. The resulting landslide susceptibility maps will be employed in environmental management. They also represent the preliminary step for the assessment of landslide hazard and risk.

The Geomorphological Map of Mt. Amba Aradam Southern Slope (Tigray, Ethiopia)

Abstract Please click here to download the map associated with this article. The geomorphological map described below covers an area of about 100 km, located on the southeastern slope of Mt. Amba Aradam (northern Ethiopia). It has been produced within the Ethio-Italian Cooperation Programme, in order to understand the recent evolution and present-day trends of the area as a basic tool for land reclamation/rehabilitation projects. The survey was carried out in three successive work campaigns (February 1995, February-March 1996 and December 2002) following the Italian Environmental Agency guidelines. The main geomorphological processes responsible for present-day landscape modelling in the investigation area, are gravity-driven mass movements and slope erosion due to running water. They strongly affect human activities, especially in terms of agriculture and infrastructure management. This map may therefore represent a useful document for land management as well as the initial step for the assessment of geomorphological hazard and risk.

Geomorphological Map of the Ionian Area between the Trionto and Colognati River Catchments (Calabria, Italy)

Abstract Please click here to download the map associated with this article. This paper describes a geomorphological map representing a sector of the Ionian coastal belt, located in north-eastern Calabria, between the catchments of the Trionto and Colognati Rivers. The landforms have been distinguished according to their origin into: a) structural and tectonic-controlled landforms; b) gravity-induced landforms; c) landforms formed by running water; d) coastal and transitional landforms; e) anthropic landforms, using as support a simplified topographic map on scale 1:20,000. The geomorphological map provides information about the long-term evolution of the landscape and identifies the geomorphic processes presently active. Therefore, the map could be used in developing land management and planning guidelines.

Landslide Hazard and Risk in the Dessie Town Area (Ethiopia)

This paper presents the results of a geo-environmental study carried out in the urban area of Dessie town, one of main urban centres of Ethiopia with 200,000 inhabitants. In this area, landslides heavily interact with a disorderly expanding human settlement, inducing high risk conditions for human lives, buildings, infrastructures and economic activities. Based on a detailed geological and geomorphological field survey and mapping, a GIS-based analysis of landslide susceptibility has been applied to the Dessie basin, one of the “hanging” tectonic depressions located along the western Afar margin. Landslide hazard and risk maps were successively produced for the central sector of Dessie town. The landslide risk map and the related report will constitute the starting point for a possible plan of risk mitigation in the urban area of Dessie.

Analysis of spatial and temporal distribution of precipitation in Trentino (Italian Eastern Alps): Preliminary Report.

The records of 92 pluviometric stations located in the Trentino Province (Italian Eastern Alps) were analyzed in order to find significant features in their spatial and temporal distribution. Differentiation of climatic regimes was detected, as well as the influence of many topographic-geographic parameters. Analyses of the data from the 20 stations with the best continuity of records indicate some periodic trends, with a major influence of those having a wavelength of ca. 26.7, 36.9 and 13.5 years. Also non strictly periodic Mediterranean oscillations influences the precipitation in the study area.

Geology of the Tekeze River basin (Northern Ethiopia)

ABSTRACT We present a geologic map of the Tekeze River basin that covers an area of ∼69,000 km2 of northern Ethiopia. The map synthesizes new data collected in two campaigns between March, 2012 and January, 2013 and compiled at a scale of 1:500,000 with published geologic surveys. The map focuses on the main geologic and tectonic features relevant to a modern interpretation of the geologic evolution of northern Ethiopia and as such, it represents an important synthesis for environmental and natural resource management.