China
Africa
Explore chapters and articles related to this topic
Desertification and Land Degradation Processes
Published in Ajai, Rimjhim Bhatnagar, Desertification and Land Degradation, 2022
Sheet erosion is the removal of soil from slopping land in a thin layer or sheet. Typically, it occurs uniformly over the entire surface of the land of a particular area of the slope. Sometimes, this kind of erosion goes on unnoticed until a significant amount of the productive topsoil has been lost. Sheet erosion is also referred to as micro-erosion or area erosion (Zachar 1982). The process of sheet erosion comprises two parts: (i) soil particles are detached from the soil by the action of falling raindrops and (ii) the detached soil particles are transported by run-off from their original place to far-away distances. In sheet erosion, uniform removal of the thin layer of soil takes place on an inclined surface because of the low kinetic energy of the run-off water. Usually, very fine particles are transported in this process of erosion.
Erosion
Published in Brian D. Fath, Sven E. Jørgensen, Megan Cole, Managing Soils and Terrestrial Systems, 2020
The most common types of soil erosion by water are sheet and rill erosion on upland areas, channel and gully erosion in small watersheds, and stream channel and bank erosion in larger catchments. Sheet erosion is caused by the action of raindrops (Figure 2) and shallow overland flows that remove a relatively uniform depth (or sheet) of soil. Because of the uniform nature of the soil loss, it is often difficult to detect and gauge the extent of damage caused by sheet erosion. On the other hand, rill erosion occurs in well-defined and visible flow concentrations or rills (Figure 3). Soil detachment in rills is large because of flow shear stress forces acting on the wetted perimeter of the rill channel (Figure 4). Once detached, larger sediment particles move as bedload, rolling and bouncing down slope with the flow, and are almost always in contact with the soil (or bed) surface. Smaller sediment particles (silts and clays) are much easier to transport and travel in the rill channels as suspended load. Rills are also the major pathways for transporting away sediment that is detached by sheet erosion (also known as interrill detachment).
Basics of Soil Erosion
Published in Abrar Yousuf, Manmohanjit Singh, Watershed Hydrology, Management and Modeling, 2019
Manmohanjit Singh, Kerstin Hartsch
Sheet erosion is defined as the uniform removal of soil in thin layers from sloping land. The top fertile soil layer is washed away from the arable lands. It can be a very effective erosive process because it can cover large areas of sloping land and go unnoticed for quite some time. Sheet erosion can be recognized by either soil deposition at the bottom of a slope or by the presence of light coloured subsoil appearing on the surface. It typically results in the loss of surface soil particles, which contains the bulk of the available nutrients and organic matter. It can also be recognized from the muddy colour of runoff water. Sheet erosion rarely flows for more than a few metres before concentrating into rills, so a better approach is to describe this phase as ‘inter-rill’ erosion, meaning both the movement by rain splash and transport of raindrop-detached soil by thin-flow surface flow whose erosion capacity is increased by raindrop impact turbulence.
Assessment of check dams’ role in flood hazard mapping in a semi-arid environment
Published in Geomatics, Natural Hazards and Risk, 2019
Mehdi Sepehri, Ali Reza Ildoromi, Hossein Malekinezhad, Afshin Ghahramani, Mohammad Reza Ekhtesasi, Chen Cao, Mahboobeh Kiani-Harchegani
Soil erosion is one of the most important environmental issues in the world (Yin and Li 2001). Soil erosion hazards involve damaging the aquatic and terrestrial environment by reducing nutrients, increasing runoff and affecting aquatic life (Langdale and Shrader 1982; Pimentel and Burgess 2013; Quinteiro et al. 2017; Mamedov and Levy 2019). Soil erosion is divided into two major groups of water and wind erosions. Water erosion is classified into sub-categories of sheet and gully erosion (Morgan and Rickson 2003). This deformation is accompanied by increased degradation and reduced permeability. There are three types of erosion in the study area, including sheet, rill and gully erosions. Sheet erosion, which is the first form of erosion, occurs in upstream regions of the catchment and gradually changes to gully erosion as it progresses to downstream regions. To assign fuzzy and entropy weights to these forms of erosion, an initial score from 0 to 10 is first assigned to them (Table 1). It should be noted that a 0 score refers to areas in which erosion has not occurred. Therefore, in the fuzzy entropy weight method, Eq. (1) is used for measuring this index, where the threshold value of the function is zero (the score of the area without erosion) and the final threshold value is related to the gully erosion score (i.e. the final threshold of land degradation). Accordingly, the fuzzy map related to erodability ranges from about 0.625 to 1. The entropy of this index ranges from 0.33 to 0.46 and 0.33 to 0.47 in the presence and absence of check dams, respectively (Figure 3).
Effects of native vegetation recovery on soil loss
Published in Journal of Applied Water Engineering and Research, 2020
Dimaghi Schwamback, Luana Lavagnoli Moreira, Daniel Rigo
Soil loss is characterized as a process of detachment and transport of soil particles by raindrops or surface runoff, followed by its deposition in areas with a lower slope. This process can be subdivided into four categories: splash, sheet, rill, and gully. The first category is due to the impact of raindrops that collide with the soil, disaggregating its particles and throwing the material up and aside. Sheet erosion is a result of the continuous and almost imperceptible runoff shear stress. The water accumulated on the surface drips according to the slope of the terrain, creating drainage lines (rills) that can aggravate and reach considerable depths, called gullies (Li and Fang 2016).
Investigation of spatial patterns erosion in the watershed of Kodar Reservoir Chhatisgarh using USPED model
Published in ISH Journal of Hydraulic Engineering, 2023
For areas affected by sheet erosion, agronomic soil protection measures can be adopted, such as contour farming, contour bunding, bench terracing etc in arable land and afforestation, degraded forests and agroforestry in barren areas. etc. can be established.