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Desertification and Land Degradation Processes
Published in Ajai, Rimjhim Bhatnagar, Desertification and Land Degradation, 2022
Mass movement or mass wasting is the downward movement of the mass of rock, debris and soil due to the force of gravity in mountainous terrain. Apart from surface erosion, mass movement is the other major land degradation process that commonly occurs in mountainous and highly undulating terrains. Surface soil erosion and mass movement have many similarities but they also differ in a certain respect. While soil erosion involves detachment, removal and transport of individual particles, mass movement or mass wasting entails the movement of relatively big masses of soil, debris and or rocks down the slope under the influence of the gravitational force of the earth. As mentioned earlier, gravity is the main force behind the mass movement, while wind and water are the principal agents for surface erosion.
Geomorphology and Flooding
Published in Saeid Eslamian, Faezeh Eslamian, Flood Handbook, 2022
Giovanni Barrocu, Saeid Eslamian
Gravity or mass erosion, also named mass wasting, consists of downslope mass movements of rock-waste mantle and bedrock. Rock parts of various shapes and sizes tend to detach and dislodge from the highest cliff elevations and precipitous crags and accumulate at their foot to form debris named screes, bordering reliefs as piedmont deposits or talus. Mass erosion, mainly acting on weathered material, affects rock fragments of size ranging from single or multiple elements of small dimensions to large volumes of landslides of various types. The term of rubble indicates screes consisting of gravel grade material (Twenhofel, 1961). Taluses are exposed to eroding agents such as streams and glaciers, which pick up portions of various debris and transport them downstream. As scree-debris continue to be weathered, they are reduced in grain size and washed downhill by rain wash. The lack of talus may be an indicator that weathered material has been removed, and the slope is unstable.
Geomorphological Studies from Remote Sensing
Published in Prasad S. Thenkabail, Remote Sensing Handbook, 2015
James B. Campbell, Lynn M. Resler
Concisely defined, mass-wasting is the bulk transport of regolith downslope, chiefly under the force of gravity, often facilitated by saturation and/or tectonic and weather events. Typical mass-wasting processes include landslides, soil creep, debris flows, and solifluction. Contributing factors often include interactions between local slope, surface materials, geologic structure, hydrology, freeze–thaw, shrink–swell, and vegetative cover, which, in specific circumstances, can assume dominant or causative roles. Masswasting events can be incremental or episodic; in some cases, discrete events are preceded by long intervals of incremental processes that set the stage for events often observed as distinct, unexpected events.
Application and comparison of logistic regression model and neural network model in earthquake-induced landslides susceptibility mapping at mountainous region, China
Published in Geomatics, Natural Hazards and Risk, 2018
Peng Xie, Haijia Wen, Chaochao Ma, Laurie G. Baise, Jialan Zhang
Vegetation can improve slope stability in mountainous region by altering the mechanical and hydrological properties of the soil and reducing surficial erosion and mass wasting. The significant impact has been understood and documented (Zhang et al. 2015). Normalized difference vegetation index (NDVI) could be seen as the parameter to measure the coverage of vegetation (Xu et al. 2013).
Hydro-geomorphic assessment of erosion intensity and sediment yield initiated debris-flow hazards at Wadi Dahab Watershed, Egypt
Published in Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards, 2021
Sara M. Abuzied, Biswajeet Pradhan
Mass-wasting represents a rapid form of erosion in which detritus, regolith, and rock fragments move downslope as continuous or discontinuous mass. The mass-wasting is the hydro-geomorphic process in which the mass movement occurs under the influence of gravity and other erosional agents. Different types of mass-wasting exist in WDW include slides, flows, topples, and falls. These types have different characteristic features and different timescales varying from seconds to hundreds of years. Commonly, the mass-wasting may cause catastrophic impacts when the area exposes to earthquakes (Kaneda et al. 2008; Owen et al. 2008; Parsons, Ji, and Kirby 2008; Gorum et al. 2011; Wasowski, Keefer, and Lee 2011). Although the mass-wasting events occur at very slow rate at WDW, the events may cause catastrophic impacts when the area receives sufficient rainfall during rainy storms or the area exposes to earthquakes. In this case, the mass-wasting occurs at very high speed, such as in rock-slides, landslides, or debris-flows with devastating impacts. Commonly, the devastating impacts take place in various zones in WDW due to debris-flows associated with erosion intensity. Several factors vary the mass-wasting potential in WDW, such as slope angle, weakening of rocks by weathering, water content, and land use/land cover (Dahal et al. 2008; Kanungo et al. 2009). Rainfall and runoff play an important role in the erosion intensity and hence in mass-wasting occurrences because the water increases or reduces the slope stability. The heavy rainfall creates large amounts of runoff that transport sediments and rock fragments down slope. Therefore, the water increases the erosion intensity and triggers the process of mass-wasting in which the rock and debris are certainly washed down slope. Debris-flows are geological processes in which runoff inducing masses of fragmented rock rush down mountainsides and then into stream channels. The debris-flows mostly have bulk densities comparable to other types of mass-wasting https://en.wikipedia.org/wiki/Landslide_classification. In most cases, the main conditions required for the initiation of debris-flows are slopes steeper than 25°, the abundant loose sediment or weathered rock, and intense rainfall to carry the loose masses to stable terrain. Debris-flows are easily recognisable in the field which generates most of debris cones along steep mountain fronts. The debris-flow deposits could be distinguished by poor sorting of sediment grains.