WHAT IS RAIN EROSION? - ENVIRONMENT - 2025

The pluvial or fluvial erosion is the manifestation of the action of the rain on the terrestrial surface. In general, erosion is the erosion of the land by forces such as water, wind and ice.

Erosion has helped form many striking features on the Earth's surface, including mountain peaks, valleys, and shores. There are many different forces in nature that cause erosion.

Depending on the type of force, erosion can occur quickly or take thousands of years. Water is the main cause of erosion on Earth, being one of the most powerful forces on the planet.

Water causes erosion through rainfall, rivers, ocean waves, or major floods.

What is rain erosion?

Pluvial erosion is one of the different types of water erosion, among which are also listed: laminar erosion, furrow erosion, gully erosion and terrace erosion.

Rain erosion is produced by the detachment and movement of thin soil particles caused by the impact of raindrops on the ground.

This causes laminar erosion, since the raindrops detach the soil particles due to the effect of kinetic energy.

Laminar erosion

Laminar erosion consists in the dragging of soil particles by rainwater in the direction of the slope. This drag can occur diffusely (barely perceptible) or uniform.

Sheet erosion develops in two stages. First of all, when the splash of rain, with its impact, hits the soil particles. Second, these particles, when detached, move downhill with the layers of flowing water carrying sediment.

Characteristics of rain erosion

Erosion is produced by the bombardment of the soil surface due to raindrops, these act as small bombs falling on exposed or bare soil. They separate the soil particles and destroy its structure.

Studies have shown that raindrops fall at speeds of up to 20 mph and can throw dirt particles as far as one and a half meters horizontally and half a meter vertically.

The drops fall in sizes up to six millimeters in diameter. A six-millimeter drop weighs 216 times more than a one-millimeter drop. Also, the heavier droplets travel at higher speeds than the small droplets.

This means that large drops carry hundreds of times more energy than small drops. Therefore, the heavier the precipitation, the larger the droplets.

This helps to explain why erosion is generally greater during short duration and high intensity storms.

Consequences of rain erosion

The strong impact of the raindrops decomposes the land mass. Lighter materials - such as fine sand, silt, clay, and organic material - that come off raindrops are more easily washed away by the current, leaving behind large grains of sand, pebbles and gravel.

These fine particles can have another effect as well. By mixing with the water in the drops, and as the water sinks into the ground, these particles clog pores in the soil that normally absorb rainwater. As a result, the floor becomes crisp and waterproof. If the area is flat, puddles begin to form.

If the area is on a slope, however, the unabsorbed water begins to flow downhill in a thin layer, carrying away soil particles that have been loosened by the bombardment of raindrops.

In this way, a single storm can remove a millimeter of dirt, which may seem insignificant, but translates to more than five tons per acre. It takes about 20 years to create that amount of soil by natural processes.

When water accumulates on the surface and the speed with which it runs off increases, a network of small channels is formed.

These channels, when joined, create other even larger channels, which progressively form furrows, ditches and, finally, larger sinkholes called “gullies”.

These channels are also polished by the dragging of the particles, gradually increasing the size of the currents, being able to dump large amounts of sediment into nearby streams and rivers.

As gully erosion increases, it can also cut below groundwater level. When this occurs, groundwater runs off and the water table falls.

Many deep-rooted plants, which protect the soil from erosion, rely more on groundwater than surface water.

Therefore, when the water table falls, it can modify conditions and reduce the ground cover in a watershed, further increasing erosion.

Geographic impact

In arid areas, rain erosion plays an important role in landscape sculpture. For example, hills and ridges formed by erosion tend to have smoothly rounded tops that are different from the sharper profiles created by other forms of water erosion.

In the field, pluvial erosion can be identified by observing small adherent soil particles on the underside of the lower leaves of the crops, visible as lumps, since it is a viscous mixture of water and colloids, which, when dehydrated, are attached to the blade.

Rain erosion can also be identified through the formation of pedestals, which is generated by fragments of gravel, minute wood chips or small fragments of tree branches.

Socio-economic impact

Water erosion, in general, causes an estimated loss of four billion tons of land each year. This translates into a significant economic loss, which includes replacing nutrients, recovering lost water, and restoring soil depth.

In addition to the cost caused by this impact, there is also the eutrophication of watercourses and lakes, the destruction of wildlife, the sedimentation of dams, reservoirs, rivers and material damage due to flooding, which are as significant as the losses. agricultural.

References

1. Núñez Solís, J. “Soil Management and Conservation” EUNED Editorial Universidad Estatal a Distancia (2001) Costa Rica.
2. "Erosion" (April, 2011) in Ecología Hoy Recovered from: ecologiahoy.com.
3. "What is rain splash erosion and why is it important?" Exploration. Vanderbilt's Online Research Magazine. (2017) Recovered from: vanderbilt.edu.
4. "Rain Erosion Damages" (2017) Poly Tech A / S Recovered from: ainerosion.com.
5. Tolhurst, TJ, Friend, PL, Watts, C. l "The effects of rain on the erosion threshold of intertidal cohesive sediments". (2006) Aquatic Ecology (Dec. 2006), Volume 40. Recovered from: Springer Link link.springer.com.
6. "The erosion of the land surface" (2017) Educational Astronomy. Recovered from: astromia.com.
7. Dr Favis-Mortlock, D. “Soil Erosion by Water” (April 2017) The Soil Erosion Site. Recovered from: soilerosion.net (2017) England.