Soil erosion

**Types of Soil Erosion**:
– Physical Processes:
– Rainfall and surface runoff produce splash erosion, sheet erosion, rill erosion, and gully erosion.
– Splash erosion ejects soil particles up to 0.6m vertically and 1.5m horizontally.
– Sheet erosion is the transport of loosened soil particles by overland flow.
– Rill erosion develops small, concentrated flow paths on hillslopes.
– Gully erosion occurs when runoff water rapidly flows in narrow channels, removing soil to considerable depths.

**River and Stream Erosion**:
– Valley stream erosion deepens valleys and extends them into hillsides.
– Bank erosion is the wearing away of stream or river banks.
– Thermal erosion weakens permafrost due to moving water, causing river channel migration and Arctic coast undercutting.
– Kolks are formed at extremely high flows, causing extreme local erosion and creating rock-cut basins.

**Erosion by Floods**:
– Kolks are formed by rapidly rushing water during floods, causing extreme local erosion and creating rock-cut basins.
– Floods can lead to significant erosion and landscape changes in affected areas.
– Large volumes of water during floods can cause rapid erosion and sediment transport.
– Examples of extreme local erosion can be seen in flood regions like glacial Lake Missoula and the channeled scablands in eastern Washington.

**Wind Erosion**:
– Wind erosion is a major geomorphological force, especially in arid and semi-arid regions.
– It causes land degradation, desertification, evaporation, harmful airborne dust, and crop damage.
– Wind erosion is primarily of two types: deflation and abrasion.
– Deflation involves wind picking up and carrying away loose particles, while abrasion occurs as surfaces are worn down by airborne particles carried by wind.

**Mass Movement**:
– Types of Mass Movement: Landslides, Rockfalls, Slumps, Creep, Debris flows.
– Causes of Mass Movement: Saturation of the ground, Oversteepening of slopes, Removal of vegetation, Earthquakes, Volcanic eruptions.
– Effects of Mass Movement: Property damage, Loss of life, Disruption of transportation, Alteration of landscapes, Creation of new landforms.
– Prevention and Mitigation of Mass Movement: Slope stabilization, Retaining walls, Drainage systems, Afforestation, Early warning systems.
– Case Studies of Mass Movement: Oso, Washington landslide (2014), Vaiont Dam disaster, Italy (1963), Thredbo landslide, Australia (1997), Vajont Dam disaster, Italy (1963), Aberfan disaster, Wales (1966).