Water erosion: definition, types, causes and consequences

Water erosion is the erosion of the land that occurs due to the passage of water . This moving water is removing material from the earth, that is, it causes soil erosion and gradually wears it down, and then deposits this material downstream. The entrained material can range from fine sandy particles to large rocks.

It is a process that contributes substantially to the modeling of the terrain , both in the material loading area and in the deposit area, and that it is necessary to take into account both in the management of natural spaces and in the management of anthropic spaces such , for example, farmlands or cities. Although it may seem vain, the conformation of the orography is a key element in our lives. In the following sections we give you some keys so that you understand why.

There are different variants of erosion due to the flow of water . This erosion depends to a large extent on whether the flow of water is continuous or not, on the speed of the water, on the obstacles that are on the way … However, we are going to see some keys to understanding the scope of this phenomenon and know the different types of water erosion :

Water erosion on the surface

The first type of water erosion that comes to mind is river water courses. Rivers and other smaller streams are responsible for shaping the terrain from high mountains to coastal areas, passing through an immense variety of intermediate forms. In general, riverbeds are V-shaped in the steepest areas, that is, in mountainous areas, while they tend to widen in the flatter areas. In addition, in mountainous areas it tends to drag larger rocks.

Underground water erosion

However, surface erosion is not the only one we find. Especially in those areas that we call karst, water also shapes the interior of the earth, giving rise to chasms and caves with spectacular formations, such as stalactites, stalagmites or flags (also called candles).

Glacial erosion

Although it is not strictly erosion caused by water, we also find glacial erosion, due to the passage of ice, which can drag large rock formations. Water also contributes significantly to erosion when freeze-fracture occurs, or rock fracture due to the freezing of water that remains between the small interstices of the rock.

We will tell you more about this topic in this other article on Glacier Erosion: definition, types and examples .

The cause of water erosion is the water cycle , one of the most important cycles of ecosystems. In short, water evaporates from large bodies of water, such as lakes and seas, and through transpiration from plants. Once in the atmosphere, it moves and the condensation of water occurs, giving rise to clouds, which in the end will give rise to some type of precipitation (snow, hail, rain …). When these precipitations fall, water courses are formed that cross the surface and the terrestrial interior until undergoing a new cycle of evaporation. It is in this last stage, in the circulation of water from higher to lower areas, when erosion occurs .

In this other AgroCorrn article you can learn more about what the water cycle is .

The consequences of water erosion go beyond changing the structure of rivers and lakes. In the modeling of the terrain we find a great variety of forms resulting from the erosion of water in the land , such as meanders, gullies, karst landscape, alluvial plains … Each of these forms has a specific development and on some occasions they are even decisive for the type of flora and fauna that settle in it or in its surroundings. A very clear example of the latter is the troglobian fauna, or fauna that lives in caves , which for the most part have been formed thanks to the erosion of water.

We also note the influence of water erosion on purely anthropic activities, such as agriculture . As we have mentioned, rivers carry various materials, among which organic matter can be found. Once deposited downstream, these nutrient-rich silts or clays act as natural fertilizer for the fields. The paradigmatic example is that of the Nile River, although it also occurs in other channels.

We have to bear in mind that we modify erosion and the water deposit to a great extent, through channels or even through dams. Especially the latter avoid the transport of materials downstream and represent a barrier to the continuity of rivers. Up to three openings can be made on the Nile (which means three harvests) per year.

Finally, we must not forget that, sometimes, our own activity can be detrimental to us when we do not take into account the relief of the terrain. This occurs when towns or cities settle on areas eroded by water, that is, by old river beds. These are the most likely passage of water, so the population centers settled in the old river beds are prone to flooding .