Water Erosion

 It is the removal of soil from the land surface by water, including runoff from melted snow and ice and is one of the major causes of soil degradation. Water erosion has been sub-divided into various types in relation to the progressive concentration of surface runoff.

Erosion of soil by water is caused by its two forms: liquid as the flowing water, and solid as the glaciers.

Forms of Water Erosion

The impact of rainfall causes splash erosion. Runoff water causes scraping and transport of soil particles leading to sheet, rill, and gully erosion. Water waves cause erosion of the banks' sides of reservoirs, lakes, and oceans. The subsurface runoff causes soil erosion in the form of pipe erosion, which is also called tunnel erosion. The glacial erosion causes heavy landslides. In India, glacial erosions are mainly confined to the Himalayan regions. The various forms of water erosion are given below.

1. Hydraulic Action: The hydraulic action takes place when water runs over the soil surface compressing the soil, as a result of which the air present in the voids exerts pressure on the soil particles and this leads to soil detachment. The soil particles so detached from their places are scoured by the running water. The hydraulic action is more effective when the soil is in loose condition.

2. Abrasion: Soil particles mixed with the running water create an abrasive power in the water which increases the capacity of flowing water to scour more soil particles. Due to this effect, larger soil particles are eroded by the flowing water.

3. Attrition: This form includes the mechanical breakdown of loads running along the moving water due to the collision of particles with each other. The broken particles are moved along with the flow velocity, which generates an abrasion effect on the bottom and banks of the watercourse. This effect pronounces the water erosion.

4. Solution: Water is a universal solvent and is associated with the chemical action between running water and soil or country rocks. This type of condition is observed in areas where existing rocks or soils are easily dissolved in the running water.

5. Transportation: The process of soil transportation by running water is completed under the following forms:

a. Solution: any water-soluble materials are transported.

b. Suspension: it involves the transportation of finer soil particles, which are not dissolved in water.

c. Saltation and Surface Creep: it involves transportation of medium size soil particles that are not able to stand in suspension form, but are mixed in water and flow over the stream bed in the form of mud. The surface creep action is responsible for transporting the coarser soil particles.

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