9.1 Types and causes of soil erosion

Soil erosion comes in various forms, each with unique characteristics. Water erosion removes soil through flowing water, while wind erosion displaces particles through air movement. Tillage erosion, caused by farming practices, moves soil downslope.

Understanding the causes and processes of soil erosion is crucial. Heavy rainfall, high winds, and intensive land use can worsen erosion. Detachment, transport, and deposition are key stages in soil particle movement. Recognizing signs of active erosion helps in early detection and prevention.

Types of Soil Erosion

Types of soil erosion

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• Water erosion removes soil particles through flowing water
  • Sheet erosion uniformly removes thin layers of topsoil across a landscape
  • Rill erosion forms small channels as water concentrates in surface depressions
  • Gully erosion creates deep channels that cannot be smoothed by normal tillage
  • Stream bank erosion undermines and collapses banks along waterways
• Wind erosion displaces soil particles through air movement
  • Suspension lifts fine particles high into the air for long-distance transport
  • Saltation bounces sand-sized particles in short hops along the surface
  • Surface creep rolls or slides larger particles along the ground
• Tillage erosion moves soil downslope through farming practices like plowing and cultivating

Causes of soil erosion

• Water erosion intensifies with heavy rainfall, loose soil structure, steep slopes, lack of vegetation, and intensive land use (deforestation)
• Wind erosion increases with high wind speeds, dry soil conditions, fine soil particles, sparse vegetation, and large open fields
• Tillage erosion worsens with aggressive implements, deep tillage, fast operation speeds, steep slopes, and frequent tillage passes

Processes of soil particle movement

• Detachment breaks soil aggregates through:
  1. Raindrop impact shattering soil clods
  2. Wind abrasion scouring exposed surfaces
  3. Mechanical disturbance from tillage implements breaking soil structure
• Transport moves detached particles via:
  • Water-driven:
    1. Overland flow carries particles in sheet erosion
    2. Channelized flow moves sediment through rills and gullies
  • Wind-driven:
    1. Suspension of dust and clay particles
    2. Saltation of sand grains
    3. Surface creep of larger particles and aggregates
• Deposition occurs when transport energy decreases:
  • Sedimentation in low-lying areas (floodplains)
  • Formation of wind deposits (sand dunes, loess)

Signs of active erosion

• Water erosion indicators reveal soil loss:
  • Exposed plant roots show topsoil removal
  • Soil pedestals form under rocks protecting underlying soil
  • Rills and gullies cut into the landscape
  • Sediment accumulates at field edges and in drainage ways
  • Muddy streams indicate suspended soil particles
• Wind erosion signs demonstrate soil movement:
  • Dust clouds appear during windy conditions
  • Sand drifts form along field boundaries and fencerows
  • Exposed subsoil or bedrock indicates severe topsoil loss
  • Sandblasted vegetation shows abrasive particle impacts
• Tillage erosion markers highlight downslope soil movement:
  • Soil accumulates at lower field edges and in depressions
  • Topsoil thins on hilltops and upper slopes
  • Lighter-colored subsoil exposed on convex slopes
  • Fence posts and structures become buried at field boundaries