Physical Degradation

Soil-Vegetation Interdependency

Plants depend on soil, soil depends on plants for stability

How does soil degradation begin, with example

Poor management, like over grazing

Avg erosion rate in US vs geological erosion

USA avg erosion is slightly above, but regionally significantly higher

3 phases of wind/water erosion

Detachment, Transport, Deposition

A problem with detachment

Surface sealing

A problem with transport

Plant damage

A problem with deposition

Raising river/reservoir bottoms causing flooding

Wind Velocity Profile

Describes wind speed changes with height above ground

Threshold velocity

Minimum wind speed to cause erosion

Soil properties that impact threshold velocity

Soil roughness, vegetation

3 wind induced soil movements

Creep (roll on ground), Saltation (short distance by air), Suspension (long distance by air)

2 differences in WEBB & RUSLE

WEPP accounts for why erosion exists. RUSLE predicts annual soil loss, not losses from single rain event.

3 water induced soil movement

Sheet erosion (evenly lost soil), Rill erosion (small channels in soil), Gulley erosion (large channels, prevent equipment use)