What two human activities could cause erosion?

Slopes slide off quickly. The reason for this is the erosion rubble, which is created over thousands of years by erosion.

Erosion is the erosion and further transport of primary particles or aggregates of the soil along the soil surface or through the air. The media that take effect here are flowing water, glacier ice, sea, wind and gravity. Theoretically, the effect occurs either linearly or over a large area, but in practice it cannot always be separated from one another.

Erosion is generally viewed as a negative phenomenon, but it should also be viewed as a natural process that occurs without human intervention and usually occurs at a low rate under natural conditions. This process is known as "natural" or "geological" erosion.
Natural erosion has accompanied the history of the earth from the time the rocks first came under the influence of the atmosphere. It forms new rocks (sedimentary rocks) from weathered rock and soil and thus shapes the surface of the land.

The speed at which natural erosion progresses depends on the soil cover, the slope, the size of the soil particles and rock fragments on the soil surface, and the general climatic conditions.

If humans intervene in the natural structure of the earth's surface through certain forms of land use, such as arable farming, clearing and overbuilding, the erosion is accelerated beyond the natural extent. This happens in more or less all parts of the world and is to be seen as the greatest factor in soil degradation.

Causes of Soil Erosion

Soil erosion is in and of itself a natural process that can be described as the removal of solid soil components by water or wind with a natural, dynamic equilibrium between soil and vegetation. However, it can be intensified by anthropogenic influences such as agricultural cultural measures, settlement and road construction or leisure facilities (e.g. ski slopes). Certain agricultural practices include: the slope and the cultivation of erosion-promoting crops, such as. B. corn and sugar beet, crucial.

Destruction of forests:
By removing the protective vegetation cover, the soil is exposed to the erosive effects of the water and the wind. Excessive water erosion often occurs on steep slopes, sliding entire slopes and losing valuable soil.

Crop production:
The soil is bare of vegetation before the rows of agricultural crops and after the harvest. Bare soil is always prone to water and wind erosion.

Cultivation on steep slopes:
The erosion is intensified by working the soil in the direction of the slope, so that channels for surface runoff are formed and erosion trenches can arise.

Intensive grazing by livestock:
A high impact load can quickly destroy the plant cover and cause wind and water erosion.

Paths and animal trails:
The entire surface runoff can collect in them. Since the infiltration is greatly reduced, groove and trench erosion can easily be triggered.

Road construction:
The increased runoff from roads and embankments leads to the formation of erosion grooves and trenches.

Mining and many other human activities always leave unprotected soil on which the forces of erosion can act more quickly.

Effect of erosion

Erosion forms more shallow landscapes when the erosion exceeds the rate of new soil formation. It therefore comes to:
  • a reduction in the water storage space and thus an increase in the risk of erosion
  • a depletion of plant nutrients and humus
  • a declining cleaning performance of the filter body and increasing pollution of the seepage water by shortening the flow and filter distance to the groundwater
  • a shortening of the soil profile and / or the exposure of inanimate, sterile soil horizons, which lead to a reduction in productivity
  • Spills and covering of seeds or young plant stands
  • a risk to the stability of plants up to and including uprooting
  • a change in the nutritional basis for organisms in the soil
  • covering, exposure or damage to parts of plants and / or their leaf surfaces by salting particles
  • a slowing down of the biological material fixation, nitrification, humification

In addition to the damage to the eroded areas, there is also damage to the places where the rock (sediment) or runoff accumulate. For example, roads are polluted, bodies of water are silted up, sediment accumulation in reservoirs, flood retention basins and dams, nutrients, pesticides and heavy metals are introduced into bodies of water and neighboring ecosystems. Due to soil erosion, entire areas of land in other climatic regions can become deserted within a few decades.

Water erosion

In water erosion, the potential energy of the water (gradient and pressure gradients) and the kinetic energy are the driving and transport forces for soil displacement.

Soil mass is carried down the slope by water that runs off the surface. The surface removal takes place on flat surfaces, the Layer- or Surface erosion is called.
When raindrops hit the ground, soil particles are thrown into the air and fine sand and silt particles are released from the aggregates. These processes are called depending on the impact of the raindrop, in water-saturated soils as Splash effect and for dry to moist soils as Impact effect. Splashing and bouncing effects are the cause of the blockage of the soil pores, the soil surface is compacted and the infiltration is reduced. If the amount of rain is greater than the infiltration capacity, the water flows off the surface.

The water often collects in grooves, furrows, ditches or canals. These can be natural sinks as well as paths, paths or tire marks and lanes of agricultural machines created by animals and humans. The deeper the water is in these depressions, the faster the runoff will be. Due to the higher discharge, the water cuts deeper and deeper into the ground, pulls more soil particles with it and forms cuts in the ground. These are known as groove erosion (small cuts) and trench erosion (deep cuts).
In trench erosion, the combination of heavy rainfall and easily erodible soil over loose or heavily weathered rock can form deep ravines. Another type of erosion is tunnel erosion. It can occur when there is a stable topsoil over an unstable subsoil and water can penetrate into the unstable zone. Tube systems are formed which can be up to 2m in diameter.

physical destruction and transportation by rain, wind, ice and running water

Wind erosion

The wind can only pick up very fine soil particles from completely or largely vegetation-free areas and carry them with it. Two factors come into play here in particular: the Wind speed and the Size of soil particles and aggregates.
Other factors would be those Grain shape, the Humidity, the Gravity and the Airtightness but these only play a subordinate role. Particularly at risk are silt and fine sand soils that are poor in humus and clay, as the soil particles are small enough and usually not aggregated. Drained and arable bogs and boggy sites are also endangered due to strong humification and can easily be blown up by the wind.

The soil particles can be transported in different ways, a distinction is made between three types of transport:

Floor creep:
Coarse particles (larger than 0.5 mm) are rolled over the surface by the wind. Soil particles up to 2 mm in size can be displaced in this way.

Saltation (term that describes the jumping and hopping movement of grains of sand):
Particles 0.05 to 0.5 mm in size are lifted up from the surface of the ground by air turbulence. However, because the particles are too heavy, they cannot be kept in the air for long periods of time. They are carried a few inches and then fall back to the surface of the ground. The energy transfer of the salting particles can also set larger particles in motion that are too heavy to be carried by the air flow alone. These can be moved rolling along the surface of the ground and destroy aggregates as well as scrape off fine parts.
Saltation causes the transport of particles of different sizes, moves approx. 50 ... 70% of the eroding masses and is therefore the most important process of wind erosion.

Particles less than 0.05 mm in diameter can be carried long distances through the air. When the soil is very dry, dust storms develop, especially in semi-arid areas, which displace large masses of soil particles.

Factors influencing water and wind erosion

Is the only variable that cannot be influenced by humans as far as possible. With increasing intensity, the ability to trigger drainage increases. The releasing effect increases as the droplet size increases.

The susceptibility to erosion essentially depends on its physical properties. The erodibility increases with the decrease in humus content, the decrease in water permeability and the increase in monovalent cations.
Soils rich in silt and fine sand are particularly susceptible, as there is hardly any structural stability and the individual grains are easy to transport.

As the third natural variable, it influences the extent of erosion primarily through the incline, length and shape of the slopes. The inclination acts through the increase in the flow speed of the draining water with increasing gradient. The longer a slope, the greater the risk of erosion compared to a shorter slope. Due to the slope shape, the amount of floor rinsing can vary considerably.

Land cover and land use
reflect the purely anthropogenic dimensions of the cultural-technical and socio-economic conditions. Covering the ground with vegetation protects the ground from the impact of drops, holds the crust in place, supports the soil structure through the roots, promotes seepage and delays surface runoff. The closer the vegetation is to the ground surface, the more effective the protection. Land use, in the form of arable farming, inevitably increases soil erosion. The protective effect listed above is all too often absent in the period without vegetation between crop rotations or in the winter fallow.
Soil tillage has a major impact on the erosibility of soils. Fine-structured fields are generally much more vulnerable than coarse clods, as the clods can minimize the impact of raindrops. On slopes, working across the slope can severely restrict water drainage, as the water can collect in all working furrows.
The choice of crop also has a significant influence on the degree of susceptibility to erosion. For example, fields on which root crops are grown are usually much more susceptible than cereal fields, as they leave a lot of soil uncovered due to the late sowing and the vastness. These fields are therefore particularly at risk during major rain and wind events.