Again the general principles behind soil erosion are illustrated, giving attention to the causes and the different soil erosion processes such as. Amelting and solidification of magma berosion and uplifting cweathering and biologic activity dcompaction and cementation 15. Watershed analysis manual bsurface erosion version 5. Water erosion is the main cause of soil degradation 1. Predicting soil thickness on soil mantled hillslopes. Runoff washes away the soil particles from sloping. It is the fairly uniform removal of soil in thin layers from the land surface, often scarcely perceptible, especially when caused by wind. Water erosion water erosion causes two sets of problems.
Rill erosion and sheet erosion are two types of soil erosion. The loss of nutrientrich topsoil from hillslopes causes severe agricultural problems for an extremely vulnerable agricultural society that depends on soil quality as a fundamental base for its livelihood. Soil erosion is defined as the process of removal of soil from one surface, due to factors like rain, wind or others, and its disposition in some other areas. The eroded material can clog soil pipes, causing pore water pressure buildup inside the pipes that can result in landslides, debris flows, embankment failures, or reestablishment of ephemeral gullies. Causes of erosion erosion occurs when soil is left exposed to rain or wind energy. Erosion from these upper watersheds is a composite of surface, channel, and.
Seepage caused tension failures and erosion undercutting. For the first 5 yr after burning, the mean sediment yield from the burned hillslopes was 32 mg ha. The numerical solution of the model was obtained by adopting the preissmann format and considering the common solution. This natural process is caused by the dynamic activity of erosive agents, that is. Which factors most directly control the development a.
Due to uprooting of trees the shortage of timber and fuel wood results. Excessive erosion can threaten the production of agricultural and forest products. Soil erosion is a process of detachment and transportation of soil by natural agencies of water and wind. Soil erosion is the process where wind, water and human beings detach soil particles and deposit them somewhere else. This natural process is caused by the dynamic activity of erosive agents, that is, water, ice glaciers, snow, air wind, plants, animals, and humans. Soil erosion is the wearing away of dirt and soil by water, wind, and human actions. Generally, where water erosion rates on disturbed upland areas are greatest, rills are active. Soil science society of america journal abstract forest. Soil creep involves the movement of slope sediments in a series of numerous cyclical steps figure 10x4. An on site loss of agricultural potential an offsite effect of downstream movement of sediment, causing flooding and the silting up of reservoirs. Erosion preceded by the destruction of the crumb structure due to the impact of falling raindrop on the surface of soil is termed as splash erosion.
Sheet erosion soil erosion is characterised by the downslope removal of soil particles within a thin sheet of water. In each nw, s, w and east facing slope three erosion plots were installed except for a north facing slope with 6 plots. Seepage caused tension failures and erosion undercutting of. Soil erosion is the displacement of the upper layer of soil, it is one form of soil degradation. Soil thickness results from the balance between the rates of soil production and transport 1,2,3 and is a critical attribute of many hydrological and ecological processes 4. Soil erosion, deposition and transport processes at. Hillslope soil erosion and runoff model for natural rainfall. Soil erosion is the wearing away of the land surface by physical forces such as rainfall, flowing water, wind, ice, temperature change, gravity or other natural or anthropogenic agents that abrade, detach and remove soil or geological material from one point on the earths surface to be deposited elsewhere. The form a hillslope takes is dependent on the various geomorphic processes acting on it. Decreasing landslide erosion on steeper slopes in soil. Effects of forest floor coverage on overland flow and soil. When the layer of topsoil is removed, ground becomes unproductive and crops decrease. The agents of soil erosion are the same as the agents of all types of erosion.
It results in loss of the finest soil particles that contain most of the available nutrients and organic matter in the soil. Does soil erosion rejuvenate the soil phosphorus inventory. Mean annual rates of soil erosion by water on these soils in fields on hillslopes up to 11 can exceed 2 kgm2 when rilling occurs, compared with a rate for top soil renewal of only about 0. Soil erosion and management activities on forested slopes. There are many factors which influence the process of soil erosion. Proposed soil erosion model soil erosion on hillslopes is a complex process that entails the processes of overland. Many potential failure modes require erosion of rock or soil to result in dam breach, such as. Evaluating soil qualitysoil redistribution relationship. There are several serious effects of soil erosion which are as follows. Goals objectives quantify erosion processes on steep loess slopes at different topographic locations as affected by different hydrologic and land management practices. Raindrops hit exposed soil with great energy and easily dislodge the soil particles from the surface.
Flow depths in rills are typically of the order of a few centimeters about an inch or less and alongchannel. Magnitude and causes ofgully erosion in the lower redwood. As an important strategy to mitigate erosion, soil conservation on hillslopes has generated significant c stabilization cobenefits by increasing the. Effects of rainfall patterns on runoff and soil erosion in.
The removal of soil in source areas leads to sediment. Using rainfall simulations, rodrigocomino et al32 compared the initial soil erosion processes in a vineyard and on abandoned land, and analysis of weathertypeinduced soil erosion in. Early estimation of the suspended sediment indicates that soil erosion in the ye l l o w river basin, china causes. May 14, 2008 by using the momentum theorem and waterbalance principle, basic equations of slope runoff were derived, soil erosion by raindrop splash and runoff were discussed and a model was established for decribing hillslope soil erosion processes. The fireenhanced soil water repellency was only stronger on the burned hillslopes than the unburned hillslopes in the first summer after burning. Hillslope soil erosion and runoff model for natural.
Soil is the most fundamental and basic natural resource for all life to survive. T value tolerable erosion equilibrium between soil gains and losses. Use of unsuitable, unrestricted cultivation of fragile soil and techniques are main causes of erosion. Soil erosion, especially in agricultural systems, affects everyone throughout the world. For example, on the upper slopes of poorly drained profiles, underlying rock may be exposed by surface erosion, and nutrientrich soils a horizon may accumulate at the toeslope. Water erosion is very simplistically speaking caused by rainfall, river flow, waves wave action, hydraulic action and abrasion, corrosion, glacier movement, thawing, etc. Workshop on common criteria for risk area identification. Effects of spatially structured vegetation patterns on. Both the fundamentals of erosion and slope stability are discussed in this chapter with respect to processes, causes and impacts. By comparing overland flow and erosion under different coverage conditions, we examined the effects of floor coverage on overland flow and soil erosion. The numerical solution of the model was obtained by adopting the preissmann format and considering the common solutiondetermining conditions, from which not.
Aug 20, 2018 soil thickness results from the balance between the rates of soil production and transport 1,2,3 and is a critical attribute of many hydrological and ecological processes 4. The universal soil loss equation usle predicts the longterm average annual rate of erosion on a field slope based on rainfall pattern, soil type, topography, crop system and management practices. The cyclical effects of temperature fluctuations, variations in moisture, and gravity on inclined soil sediments often cause this process. Soil residence time soil age soil erosion hillslopes soil chronosequences soil parent material abstract phosphorus p is an essential nutrient for life. We propose that faster rates of soil creep on steeper slopes cause thin and more stable soils, which in turn reduces landslide erosion, despite the added. Soil erosion is a major factor of land degradation in subsaharan africa. Field observations and experimental work, however, show that the form of the cover. The outcomes of soil erosion are reduced agricultural productivity, ecological collapse, soil degradation, and the possibility of desertification. Overtopping erosion of an embankment overtopping erosion of a concrete dam abutment or foundation erosion of an unlined spillway or river channel erosion of an unlined plunge pool leading structural undermining. A soil p paradigm based on studies of soils that form on. A gully is a distinct channel, carved into a hillslope or valley bottom by intermittent or ephemeral.
Which factors most directly control the development asoil. The impact of natural hillslope processes is important and is currently strongly influenced by human activity due to land use change and vegetation removal, and is becoming even greater due to climate change. Amelting and solidification of magma b erosion and uplifting cweathering and biologic activity dcompaction and cementation 15. A general trend of decreasing soil loss rates with increasing vegetation cover fraction is widely accepted.
Soil compaction, low organic matter, loss of soil structure, poor internal drainage, salinisation and soil acidity problems are other serious soil degradation conditions that can accelerate the soil erosion process. Soil movement by tillage controlled the despite intensive studies of soil erosion over the last spatial patterns in om, n, and p on both terraced and steep cultivated 40 yr on chinas loess plateau, effects of erosion on hillslopes. Th is can occur when the concentration of fl ow into soil pipes exceeds their transport capacity or when blockage of the soil pipe by eroded material causes a buildup of internal water pressures in the soil pipe. Erosion may also impact water conveyance and storage structures, and contribute to pollution. Soil erosion is harmful and useful at the same time. Workshop on common criteria for risk area identification in. The ability of rainfall to cause soil detachment and transport. Erosion can be a problem because it carries the nutrients of the soil away. An onsite loss of agricultural potential an offsite effect of downstream movement of sediment, causing flooding and the silting up of reservoirs. Hillslope erosion by water erosion is driven by horton overland flow, which primarily. The thickness and composition of soil horizons vary with position on a hillslope and with water drainage. Spatial variability of soil erosion and soil quality on.
Dec 18, 2007 the fireenhanced soil water repellency was only stronger on the burned hillslopes than the unburned hillslopes in the first summer after burning. Soil erosion is an extremely dynamic and complicated process. Soil erodibility and processes of water erosion on hillslope. Rainfall energy is the prime cause of erosion from tilled or bare land. Water erosion is caused by the detachment and transport of soil by rainfall, runoff, melting snow or ice, and irrigation. Watershed analysis manual bsurface erosion appendix b. The usle experimental design included monitoring replicated hillslopes with the. Runoff washes away the soil particles from sloping and bare lands while wind blows away loose and detached soil particles from flat and unprotected lands. Gilley, in encyclopedia of soils in the environment, 2005. Soil loss is so gradual that the erosion usually goes unnoticed, but the cumulative. Preferential flow through soil pipes results in internal erosion of the pipe, which may produce gullies by tunnel collapse. Yang2 1 institute of mountain hazards and environment, chinese academy of sciences, p. Aug, 2018 the direct reduction of soc mobilization caused by decreased soil erosion is primarily the result of soil conservation on hillslopes fig. By using the momentum theorem and waterbalance principle, basic equations of slope runoff were derived, soil erosion by raindrop splash and runoff were discussed and a model was established for decribing hillslope soil erosion processes.
Human activities can significantly accelerate erosion resulting in the soil loss. One of the most widespread of these processes is soil creep. Th e fi reenhanced soil water repellency was only stronger on the burned hillslopes than the unburned hillslopes in the. Rill erosion involves flow concentration, often caused on natural hillslopes by microtopography, vegetation, or animal tracking. Soil erosion is affected by many factors, among them topographic position of slope, vegetation and soil type have a momentous role on erosional behavior of soil morgan, 1986.
Usle only predicts the amount of soil loss that results from sheet or rill erosion on a single slope and does not account for additional soil. Modeling soil erosion and reservoir sedimentation at. Running water is the leading cause of soil erosion, because water is abundant and has a lot of power. It is the fairly uniform removal of soil in thin layers from the land surface, often. Thus, soil erosion is a continuous process and may occur either at a relatively unnoticed rate or an alarming rate contributing to copious loss of the topsoil. Effective soil erosion control represents a significant net. Evaluating soil qualitysoil redistribution relationship on. Nearing abstract the form of dems is more explicit and detailed than data on soil erosion at the slope scale is essentially limited to information often used in the past.
Effects of land use and slope gradient on soil erosion in a. Sheet erosion sheet erosion is the removal of soil in thin layers by raindrop impact and shallow surface flow. The spatial and temporal variability of this phenomena are very high within a catchment. Sep 21, 2017 soil erosion is the process where wind, water and human beings detach soil particles and deposit them somewhere else. Wind is also a leading cause of soil erosion because wind can pick up soil and blow it far away. On most hillslopes large quantities of soil and sediment are moved over time via the mediums of air, water, and ice often under the direct influence of gravity. The main causes of soil erosion are still inappropriate agricultural practices. Seepage caused tension failures and erosion undercutting of hillslopes m. The greatest challenge for sustainable soil management. Wilson d a department of biosystems and agricultural engineering, oklahoma state university, 209 agricultural hall, stillwater, ok 74078, united states b department of biosystems and agricultural engineering, oklahoma state university, 120 agricultural hall. In earth science, erosion is the action of surface processes such as water flow or wind that removes soil, rock, or dissolved material from one location on the earths crust, and then transports it to another location not to be confused with weathering which involves no movement. We applied this information to a soil erosion model and then evaluated the dominant mechanism for reducing.
Normal rate of erosion keeps the soil profile stable under the current climate. Vast areas of gentle slope lands soil erosion on forested hillslopes with different floor coverage. Water erosion processes on hillslopes soil erodibility can be defined only in relation to specific erosion processes and erosive forces, so discussion of critical process characteristics is essential in understanding the effect of the dynamics of related soil. A case study in the denku microwatershed oromia region by kassu kebede beyene submitted in accordance with the requirement for the degree of masters in human ecology at the university of south africa supervisor. The spatial variability patterns of soil erosion and their impacts on soil quality within the landscape is being considered as a basis for making management decisions for s u s t a i n a b le cropping systems in china. Precipitation is the most forceful factor causing erosion. Rill erosion refers to the development of small, ephemeral concentrated flow paths which function as both sediment source and sediment delivery systems for erosion on hillslopes. Predicting soil thickness on soil mantled hillslopes nature.
The cross section below shows soil layer x, which was formed from underlying bedrock. Which change would most likely cause soil layer to increase in thickness. Effective soil erosion control represents a significant. The erosion by water is most prevalent in regions with high relief, although it can occur even in land with quite moderate slopes. This can make the quality of crops grown on a piece of land go down over time.
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