Dr Stefan Krause, Keele University, [email protected]C-Change in GEES: Human Pressures on the Environment – Mass Movement, Weathering and Erosion C-Change in GEES Human Pressures on the Environment Session 2 Session 2: Mass Movement, Weathering and Erosion
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Dr Stefan Krause, Keele University, [email protected] C-Change in GEES: Human Pressures on the Environment – Mass Movement, Weathering and Erosion.
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C-Change in GEES: Human Pressures on the Environment – Mass Movement, Weathering and Erosion
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C-Change in GEES: Human Pressures on the Environment – Mass Movement, Weathering and Erosion
Soil moved by air - similar to water erosion
Fine particles are moved easily, if as small as clay and silt, they can become airborne
Sand particles between 0.1 and 1 mm move by saltating (jumping) over the ground, like a sheet. Heavier particles move by rolling. Unlike water, wind can move soil over very large distances of thousands of kilometres and over seas to other countries.
C-Change in GEES: Human Pressures on the Environment – Mass Movement, Weathering and Erosion
Rainfall: Amount, intensity, and frequency – due to high soil moisture and saturated conditions during periods of frequent rainfall, a greater percentage of the rainfall will become runoff
Temperature: Frozen soil is highly resistant to erosion, rapid thawing of the soil surface brought on by warm rains can lead to serious erosion.
Erosion intensity dependent on type of precipitation – e.g. falling snow does not erode, however, heavy snow melts in the spring can cause considerable runoff damage.
Influences the amount of organic matter that collects on the ground surface and incorporates with the topsoil layer. Organic matter protects the soil by shielding it from the impact of falling rain and soaking up rainfall that would otherwise become runoff.
Warmer climates - thinner organic cover on the soil.
C-Change in GEES: Human Pressures on the Environment – Mass Movement, Weathering and Erosion
Erodibility influenced by texture (size or combination of sizes of the individual soil particles), structure and cohesion
Silt rich soils are most susceptible to erosion from wind and water
Clay or sand-sized particles are less prone to erosion.
Structure influences both the ability of the soil to absorb water and its physical resistance to erosion.
Cohesion refers to the binding force between soil particles and influences the structure. When moist, the individual soil particles in a cohesive soil cling together to form a doughy consistency. Clay soils are very cohesive, while sand soils are not.
C-Change in GEES: Human Pressures on the Environment – Mass Movement, Weathering and Erosion
Slope length, steepness and roughness affect erodibility. Generally, the longer the slope, the greater the potential for erosion. The greatest erosion potential is at the base of the slope, where runoff velocity is greatest and runoff concentrates.
Slope steepness, along with surface roughness, and the amount and intensity of rainfall control the speed at which runoff flows down a slope. The steeper the slope, the faster the water will flow. The faster it flows, the more likely it will cause erosion and increase sedimentation.
Slope Characteristics
Waltham, T., (2009) Foundations of Engineering Geology. 3rd edition, Spon:
C-Change in GEES: Human Pressures on the Environment – Mass Movement, Weathering and Erosion
Riparian fencing: protecting slopes from cattle trampling – allows vegetation to regrow
Shelter belts and grassed waterways : vegetation growth at field boundaries
Spaced tree planting: roots hold soil and cycle nutrients
Reduced tillage: tilling only the areas that matter while minimally disturbing the soil. Tilling between furrows. Stubble-mulching: leaving stubble on the field as long as possible to reduce evaporation and keep the soil covered. Stubble has to be mulched rather than ploughed.
Contour ploughing: works a bit like terracing, preventing moisture from running down-hill and reducing erosion considerably.
Terracing: extensively practised in padiculture – drastic erosion management measure
Reduced compaction: using machinery and technology that spreads its weight over a larger area.
Optimal fertilising: avoiding degradation of soil from over-fertilising
C-Change in GEES: Human Pressures on the Environment – Mass Movement, Weathering and Erosion
Erosion Management: Agriculture
Stubble-mulching: leaving stubble on the field as long as possible to reduce evaporation and keep the soil covered – important for the prevention of wind erosion, particularly common in US Great Plains.
Contour ploughing: Ruts made by the plough run perpendicular rather than parallel to slopes. The rows formed slow water run-off during rainstorms to prevent soil erosion and allows the water time to settle into the soil.
C-Change in GEES: Human Pressures on the Environment – Mass Movement, Weathering and Erosion
Erosion Management: Agriculture
Terraced land around Konso in Southern Ethiopia
Terracing: This form of land use is prevalent in many countries, and is used for crops requiring a lot of water, such as rice. Terraces are also easier for both mechanical and manual sowing and harvesting than a steep slope would be.
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