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A Students Guide to Water Erosion

Water erosion is the process where water damages natural earth material or man-made structures like houses and carries away the broken off parts. Although this process is largely natural and can be done by rain, streams, rivers, and other acts of water moving, some human acts have contributed to or furthered the process. Erosion can be as simple as water moving down a hill and creating small grooves, or as disastrous as destroying buildings and homes. Many factors will affect what erosion can do: water volume, wind, topography, and soil composition can all determine how much damage will be done, if any. When you are talking about erosion by water it's important to know exactly what it is, the various types of erosion, and how it works.

Erosion Definition

Erosion by water simply is the breaking down of rock into smaller pieces by water. This act of natural weathering can damage anything from the smallest rocks on flat ground to entire towns. Because of human acts, running water is more able to damage the ground because there is less coverage protecting it from being weathered down. Human creations like roads, city expansion, and industrial farming all make the ground more prone to damage. Running water has been a leading factor in shaping the world today – continents, entire civilizations, trade routes, and other parts of the lives of people have all been affected by rain and other acts of moving water.

How Water Erosion Works

The act of erosion really is as simple as water, regardless of how much, hitting rock or another physical object and chipping away tiny pieces. Erosion can be as small as a single raindrop falling from the sky and scattering miniscule rock particles on the ground, or as large as a flood running through a town and damaging walls and windows. When running water picks up objects such as rocks and clay, it will chip away at whatever it's running through (like a stream or on a hill) causing more parts to break off – even larger chunks of rock. Example: a running river will pick up random rocks from the bottom. Those rocks will chip away at the sides or base of the river, and keep moving forward chipping away more and larger pieces. Most common forms of erosion aren't easily noticeable and may take years to make an obvious difference, such as a wider river, a flatter hill, or a worn out side of a building. Another good example are waves hitting a beach – each time a wave beats on the beach, more bits of sand are pulled back out into the water because of the strength of the water.

Types of Water Erosion

No two forms of erosion work the same way or cause the same amount of damage. Some types of water erosion can be a simple scattering of rock, or even removing huge chunks of rock from the wall of a river. For rill and gully erosion, if there is enough rain and if it's intense enough, then the runoff can lead to noticeable erosion. If not all of the rain is absorbed by the ground as it runs down the hill or other surface, then it will lead to runoff – if there is enough it can cause flooding, if not then it will linger around until it is absorbed.

Sheet Erosion: The removal of a thin soil layer from a large area.

Rill Erosion: A series of small grooves on a sloped mass caused by rushing water, such as on a field or a hill. These channels are generally quite shallow and on average are less than two inches deep.

Gully Erosion: Running water creates large and wide channels that are frequently big enough so they can't be made smooth by standard tillage equipment.

Splash Erosion: The movement of particles by the splash of water – soil can be thrown multiple feet in a single raindrop. This method can only really cause damage if the rain is coming down hard, fast, and in a large volume, otherwise it won't do anything noticeable and will just move tiny pieces that we can't see. Splash erosion barely even breaks anything off – if anything, it only redistributes the already detached particles.

Below is a list of resources that will expand on the erosion definition, how the process works, and what other factors may contribute to erosion such as wind and gravity.


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