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Desertification and Land Degradation Processes
Published in Ajai, Rimjhim Bhatnagar, Desertification and Land Degradation, 2022
Gully erosion can be thought of as the next stage of rill erosion. Gullies are normally formed due to the accumulation of larger quantities of run-off water or the gradual deepening of rills (Figure 4.1). These are, basically, the intermittent stream channels larger and deeper than the rills. The depth of gullies is larger than 30 cm. They are usually formed when several rills join together and further extend with more than 30 cm depth. Gullies are usually formed in the areas where a large volume of run-off water are concentrated and discharged on to slope with erodible soils. On the basis of size, gullies can be classified as small (depth less than 1 m), medium (depth between 1 and 5 m) and large (depth greater than 5 m). Based on the forms of erosion, gullies are classified as flat, narrow, broad and round gullies. Flatforms of gullies, generally found in shallow soil, are characterized by a broad V-section. In this case, lateral erosion prevails over vertical erosion. ‘Narrow' forms of gullies have a narrow V-shaped section. In this case, the breadth of the gullies is normally equal to or smaller than the depth. Broad gullies have a U shape in cross-section with a wide bottom. In this case also, lateral erosion is more than depth erosion. Details of the various forms of gullies are discussed by Zachar (1982). Since gullies are bigger in size, they cannot be obliterated by normal tillage or grading.
Basics of Soil Erosion
Published in Abrar Yousuf, Manmohanjit Singh, Watershed Hydrology, Management and Modeling, 2019
Manmohanjit Singh, Kerstin Hartsch
Gully depth is often limited by the depth to the underlying rock which means that gullies are normally less than 2 m deep. However on deep alluvial and colluvial soils, gullies may reach depths of 10 to 15 m. The rate of gully erosion depends primarily on the run off producing characteristic of the watershed, the drainage area, soil characteristics, the alignment, size and shape of the gully and the slope of the channel. Gullies pass through successive cycles of erosion and deposition. It is not uncommon for the head of a gully to be extremely active while the lower section of the gully is stabilizing.
Erosion
Published in Karlheinz Spitz, John Trudinger, Mining and the Environment, 2019
Karlheinz Spitz, John Trudinger
Terraces, check dams, tillage, and other grading measures can be utilized to reduce erosion and to ensure slope stability. Such measures are designed to minimize both the quantity of flow and its velocity. Site drainage should be designed to control rill erosion and to prevent deepening or enlargement of channels, which can eventually lead to the development of gullies.
Robustness analysis of machine learning classifiers in predicting spatial gully erosion susceptibility with altered training samples
Published in Geomatics, Natural Hazards and Risk, 2021
Tusar Kanti Hembram, Sunil Saha, Biswajeet Pradhan, Khairul Nizam Abdul Maulud, Abdullah M. Alamri
Gully is the most visible expression of soil erosion and can be defined as a channel with >0.093 square metres cross-sectional area (USDA-SCS 1966; Poesen et al. 1996). The gully-affected areas are designated with some harmful characteristic such as unproductive and degraded land, soils with low nutrients and high contaminants, drainage sedimentation, desertification, destruction of roads and anthropogenic infrastructures (Poesen et al. 1998; Fox et al. 2016). Ekholm and Lehtoranta (2012) pointed out that from an ecological perspective, gully erosion decreases the surface vegetation cover and accelerates the process of desertification. Gullies are formed when erosion by water or erodibility of the soils is greater than the geomorphic threshold of the specific unit or an area (McCloskey et al. 2016). Gully formation and development, within a river basin or specific unit, is controlled by numerous factors, i.e. climatic characteristics, soil type and properties, drainage characteristics, anthropogenic activities and various favourable topographical attributes (Rahmati et al. 2016; Piacentini et al. 2018). Alternative dry-hot and wet seasons accelerate gully erosion during boiling and dry summer, with the presence of favourable soil and wilted vegetation, fine cracks appear on the dried soil surface (Roose 1996). Thereafter, during wet season, the first quick precipitation concentrates in these cracks, and the flow velocity and volume of water get increased and stimulate the erosive power, which leads to the formation of rill and gullies (McCloskey et al. 2016).
Head-cut gully erosion susceptibility modelling based on ensemble Random Forest with oblique decision trees in Fareghan watershed, Iran
Published in Geomatics, Natural Hazards and Risk, 2020
Quoc Bao Pham, Kaustuv Mukherjee, Akbar Norouzi, Nguyen Thi Thuy Linh, Saeid Janizadeh, Kourosh Ahmadi, Artemi Cerdà, Thi Ngoc Canh Doan, Duong Tran Anh
Gully erosion is characterized by severe soil erosion over short periods of time (Torri and Borselli 2003). Gullies devastate soil and water resources and impact on agricultural productivity and aquatic biodiversity (Zabihi et al. 2018; Zabihi et al. 2019; Nhu et al. 2020). Gullies development is a widespread cause of land and geo-environmental degradation in semiarid and arid regions, where land use and land management contributed to accelerated soil erosion processes, with gullies as the main landforms (Rahmati et al. 2016; Arabameri, Rezaei, et al. 2018; Arabameri, Pradhan, Pourghasemi, et al. 2018; Garosi et al. 2019) and can intensify the off-site impacts of water erosion (Poesen et al. 2003). Head-cuts within gullies represented an important feature in the Earth landforms and soil erosion behaviour. Head-cuts are vertical steps which erode the valley network by travelling back in the hillslopes (Bull 2002; Poesen et al. 2002) and increase sediment delivery to the gully system (Berlin and Anderson 2007; Rengers and Tucker 2014). To survey the gully system it is necessary to determine the magnitude and spatial distribution of head-cut gully erosion susceptibility zones, and this will be the bases to achieve a sustainable management upon the gully growth.