Water Erosion: Types, Causes, Effects, And Prevention

What Is Water Erosion?

Water erosion is the removal of the top layer of land by water from irrigation, rainfall, snowmelt, runoff, and poor irrigation management. Ultimately, rainwater is most frequently to blame when it comes to this issue. The flowing water moves the soil organic and inorganic particles alongside the land surface, depositing them in the lower landscape, as is typical for hillside erosion. The result of this would be flooding in the long run. The eroded soil material can either form a new soil or move to water reservoirs nearby (lakes, streams, etc.).

What Are The Causes Of Water Erosion?

Depending on the cause of its occurrence, land depletion by water can be either natural or accelerated. Natural water erosion is beyond human control and does not have a significant effect on soil fertility. It is caused by rainfall, melted snow, or runoff, i.e the natural forces. Each soil type has its natural erosion rate, depending on farmland properties and the climate in which it is located.

On the contrary, accelerated erosion is the consequence of irrational farming. It occurs when the wrong choice of irrigation method, amount of water, and the time of its application result in the destruction of the fertile layer of land.

Different Types Of Water Erosion

Land depletion caused by water occurs in several stages and is manifested in different ways according to the factors that caused it. Below are the common water erosion types that can affect soil if not prevented promptly.

Splash Erosion

This is the first stage in the erosion process that is caused by rain. Raindrops basically “bombard” the exposed and bare land, moving its particles and destroying the structure of the top layer. Eventually, it causes the formation of surface crusts, negatively affects soil infiltration ability, and eventually results in runoff formation.

Sheet Erosion

This type of soil degradation by water occurs when the rainfall intensity is greater than the soil infiltration ability and results in the loss of the finest soil particles that contain nutrients and organic matter. It usually follows after crusting that is caused by the previous stage of soil damage by water. If not prevented timely, one of the most negative effects of sheet erosion will be the formation of rills.

Rill Erosion

Rill erosion follows after, when the water concentrates deeper in the soil and starts forming faster-flowing channels. These channels can be up to 30cm deep and cause detachment and transportation of soil particles. Rill erosion can eventually evolve into gully erosion. That is when the rills become at least 0.3m deep.

Gully Erosion

This is an advanced stage of land damage by water when the surface channels are eroded to the extent when even tillage operations wouldn’t be of any help. Apart from causing huge soil losses and destroying farmland, it also results in reduction of water quality by increasing the sediment load in streams.

Tunnel Erosion

This is the so-called “hidden” type of land degradation by water that can cause severe disruption even before any signs are evident to the eye. It begins when large water mass starts moving through the structurally unstable soil. That is why it is usually the biggest threat to sodic soil. The manifestations of tunneling would be a series of tunnels beneath the soil surface.

What Are The Negative Effects Of Water Erosion?

Despite the diversity of manifestations, all types of water erosion cause a common set of negative effects that can be defined.

Impact On Flora

The removal of topsoil due to the fast land degradation process will inevitably affect the plants that grow there. The reduction of nutrients that were washed out from the soil by the excess water will prevent crops from receiving the necessary amount of needed elements that decreases their performance.

Impact On Fauna

Soil health depletion doesn’t go unnoticed for the living organisms too. The absence of the topsoil surface leads to water pollution due to chemical runoff, negatively affecting animals, fish and algae in the area. Eventually, this leads to reduction of the animal population.

Flooding

Severe land degradation by water can negatively impact the ecosystems ^{What is Erosion? Effects of Soil Erosion and Land Degradation. worldwildlife.org} by causing flooding. The washed away topsoil loses its water absorption ability, greatly increasing the possibility of flooding in areas that are predisposed to it. It could be low-lying landscapes and soils with limited drainage ability. Ultimately, heavy flooding can be extremely disruptive to the extent of ruining roads and buildings. That is why it’s critical to spot negative changes in farmland health to prevent the situation from getting to that point.

Impact On Water Quality

Apart from affecting animals, plants, and farmland, water erosion also significantly decreases the quality of water itself. The particles of the eroded soil eventually reach the water sources nearby, changing the water chemical content and reducing its oxygen levels. Besides, the water from eroded farmlands contains harmful chemicals (due to previous pesticides application), washing them off to lakes, streams, and rivers.

How To Stop Water Erosion & Its Management

Water erosion control is vital in battling the issue of land degradation caused by water. And the water erosion solutions differ depending on the type of soil, topography, climate, crop rotation, and land use. However, there are water erosion prevention measures for its every type.

The table below shows both the common and the most useful control measures for different types of water erosion.

How To Prevent Splash Erosion

Studies claim that the key in preventing this type of soil degradation is to maintain the ground cover at levels not below 70% ^{Steven Cork, Laura Eadie, Pauline Mele, Richard Price, Don Yule. (2012). The relationships between land management practices and soil condition and the quality of ecosystem services delivered from agricultural land in Australia.} (80-100% at the slopes that face the North), ensuring there is no threat of soil particles detachment that can lead to the next erosion stages. Ultimately, ground cover maintenance is the best method of controlling splash erosion.

To assist with that, EOSDA Crop Monitoring offers a number of vegetation indices that help to evaluate not only the quality of the crops but distinguish covered with plant areas of the field and bare soil. It is especially useful

• between growing seasons when the cash crops are already harvested;
• in the cold periods of the year, to monitor winter cover crops;
• when the field is left unseeded (fallow);
• when the field is temporarily converted into grass pasture (convertible husbandry).

Sheet Erosion Prevention

Sheet erosion control starts with the maintenance of ground cover, soil structure, and soil organic matter. This prevents the development of splash erosion by preventing topsoil compaction. Another protection option is the use of mulch to cover the land surface.

As the productivity of the field can decrease after such soil degradation, EOSDA Crop Monitoring enables farmers to monitor the productivity of a separate field not only throughout the season but in the long run too. Season by season, a farmer can compare the productivity areas of the field and identify the problem sites. Setting the scouting tasks helps effectively check weather water erosion processes present in the field and implement timely management strategies.

Rill Erosion Prevention

The only way to prevent rill erosion at the stage when the runoff has already formed is to reduce the waterflow speed and harden the soil. One of the best ways to slow down the waterflow is to protect the land surface with the growing plants cover or a crop residue. And soil hardening can be ensured by correct crop rotation.

How To Prevent Gully Erosion

Not to allow this type of soil health degradation, the farmers need to minimize tree clearing and prevent moisture concentration into gullies from buildings, roads, and stock routes.
Gully erosion control methods are basically a combination of approaches that aim to avoid extra water access to the land. Such ways of controlling gully erosion imply the use of fencing, banks and different engineering constructions to avoid extra water access to the land.

Tunnel Erosion Prevention

Preventing tunnel erosion is not an easy task. Only a few are successful in it. This type of erosion is not only difficult but expensive to control. It requires the use of chemical, mechanical, and vegetative forces to prevent tunnelling and influence its further development. Chemical amelioration implies high applications of gypsum and / or lime in farmland treatment to ensure electrolyte balance. Regular soil testing helps not only to identify tunnel erosion timely but also make important tests for pH level, electrolyte concentration, etc. and ensure correct chemical amelioration.

The already damaged fields with tunnel erosion require not only chemical amelioration but application of fertilizers to the areas that suffer from decreased productivity. In this case, differentiated fertilization is the best option. Variable rate technology used by EOSDA Crop Monitoring divides the field into different areas, considering the productivity of the planted crops. Such an approach helps to maximize yields of a damages field as well as reduce an impact of chemicals on the soil.

Maintaining the soil healthy and preventing it from occurence of any type of water erosion is one of the essential tasks of any agronomist. EOSDA Crop Monitoring helps not only in remote spotting and controlling of soil damage caused by water, but also assists growers throughout the whole process of crop growing, from seeding to harvesting.