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Mass movements
Published in F.G. Bell, Geological Hazards, 1999
An earthflow involves mostly cohesive or fine-grained material, which may move slowly or rapidly. The speed of movement is to some extent dependent on water content in that the higher the content, the faster the movement. Slowly moving earthflows may continue to move for several years. These flows generally develop as a result of a build-up of pore water pressure, so that part of the weight of the material is supported by interstitial water with consequent decrease in shearing resistance. If the material is saturated, a bulging frontal lobe is formed and this may split into a number of tongues, which advance with a steady rolling motion. Earthflows frequently form the spreading toes of rotational slides due to the material being softened by the ingress of water. Skempton and Hutchinson (1969) restricted the term ‘earthflow’ to slow movements of softened weathered debris, as forms at the toe of a slide. They maintained that movement was transitional between a slide and a flow, and that earthflows accommodated less breakdown than mudflows.
Potential climate changes in Italy and consequences for land stability
Published in Ken Ho, Suzanne Lacasse, Luciano Picarelli, Slope Safety Preparedness for Impact of Climate Change, 2017
L. Picarelli, L. Comegna, S.L. Gariano, F. Guzzetti, P. Mercogliano, G. Rianna, M. Santini, P. Tommasi
For this category of movements, the expected climate changes could increase the incidence of re-activations due to intense precipitations and it could further reduce the displacement rate in the steady-state stage because of the decrease in the cumulated yearly rainfall. Based on investigations of the Costa della Gaveta landslide, in the Basento River valley, Comegna et al. (2013) proposed a methodology based on the coupling of climatic scenarios and geotechnical analyses with the goal to predict the future behaviour of the earthflow. The approach includes: (i) the calibration of a model linking weather parameters and pore pressure regime, (ii) the definition of a relationship between pore-water pressure and landslide movement, and (iii) the assessment of the long-time landslide behaviour based on the available climate scenarios. Studying historical daily rainfall and temperature records for the Costa della Gaveta landslide landslide, they found a negative trend in rainfall (–2.4% per decade) and a slightly positive trend in temperature (+0.04% per decade). Through the regional climate model COSMO-CLM, a simulation of the climate in the Mediterranean area for the period 1965–2100 was then performed. As a result of the expected future decrease in precipitation and increase in temperature, the Authors obtained a reduction in the groundwater level of about 8 mm per decade. By means of the relationship between pore pressure and landslide velocity, they calculated a decrease in the displacement rate of 1.5–3.0 mm/decade, leading to a maximum total displacement of 77–86 cm over next 50 years. In the considered case, the climatic changes are not expected to play a relevant role on the behaviour of the earthflow, providing useful information for planning purposes.
Geotechnical aspects of landslides in the Alps
Published in Jan Rybář, Josef Stemberk, Peter Wagner, Landslides, 2018
Earthflows are mass movements in predominantly deeply weathered claystones and marl formations. In the sense of Hutchinson (1988), these movements are relatively slow moving, commonly lobate or elongate masses of accumulated debris in a softened clayey matrix that advance chiefly by sliding on discrete bounding shear surfaces. The surface relief governs the course and form of an earthflow. Earthflows generally start out in a large basin in the upper part of the slope where slope debris and weathering material have accumulated. The front of such earthflows is often the starting point of devastating debris flows.
Geological and geophysical characterization of the Brindisi di Montagna Scalo landslide (Basilicata, Southern Italy)
Published in Geomatics, Natural Hazards and Risk, 2019
Mario Bentivenga, Alessandro Giocoli, Giuseppe Palladino, Angela Perrone, Sabatino Piscitelli
The BMSL is located in the central part of the Basilicata Region, a few kilometres east of Potenza, which coincides with the high-middle sector of the Basento River. The BMSL is part of a 3 km2 wide area, extending from Tempa Pizzuta to the Basento River, largely affected by slope instability (Figure 2). It is possible to subdivide this area into two distinct sectors. The first sector, encompassing the top of Tempa Pizzuta Hill (770 m above sea-level – asl) to the SP n. 37 (at a height of 675 m asl) (Figures 1 and 3), is characterized by gently-dipping slopes, competent lithologies pertaining to the Flysch Rosso, the clayey–marly interval and the Pre-numidian interval and dormant landslide activity. The second sector, included between the SP n. 37 and the Basento River bottom (500 m asl), is characterized by high acclivities, clayey lithologies, belonging to the Flysch Rosso, Argilliti e radiolariti di Campomaggiore and the Gorgoglione Formation, and intense landslide activity. The BMSL is the most significant feature observable in the second sector. The entire area shows an average slope acclivity of about 10°. It is located between the mountain and hill altitude zones and, similar to great parts of the Southern Apennine area, the observed morphology is the result of two main concomitant factors that have controlled landscape modelling: (i) Pliocene to Quaternary regional uplift, and the consequent increase in fluvial incision; (ii) lithology, and the structural arrangement of the outcropping formations. General features of the area include the occurrence of ephemeral streams, encased in narrow and deep incisions, and abrupt acclivity change that commonly corresponds to tectonic structures and lithological variations (for example, at the boundary of the Argilliti e radiolariti di Campomaggiore and Flysch Rosso). At the base of the slope, the Basento River has a roughly rectilinear path, which is only deflected where it meets the toe of the BMSL. Tributary streams also display a parallel and rectilinear path, sometimes originating from springs that are subject to strong seasonal variations. In the study area, springs have commonly been observed to appear at the boundary between the Argilliti e radiolariti di Campomaggiore and the overlying Flysch Rosso, or in the more fractured portion of the Flysch Rosso succession. The main geomorphologic instabilities are observed in the argillaceous parts of the Sannio Unit. In the geomorphological map in Figure 2, different landslide types, affecting the investigated slope, have been reported, according to Varnes (1978). Earthflows are the most commonly recognized landslide type. Complex, rotational and translational slides are also common.