Erosion, Erosion, Everywhere

 

Main Objectives

1.Capable of describing the magnitude of accelerated soil erosion in the past and at the present.

2.Comprehend the mechanics and the factors influencing water erosion

3.Understand wind erosion in terms of particle movement on a surface, and the factors that change soil erosion by wind.

Key Terms and Concepts

Raindrop splash
Sheet erosion
Rill and gully erosion
Universal Soil Loss Equation
Wind erosion equation

1. The problem of soil erosion

Natural (geologic) erosion (<2 Mg/ha/yr. Forest <0.1 Mg/ha/yr) vs. accelerated erosion (up to 1000 times higher)

(1) On-site: loss of topsoil (nutrient, water, etc.)

(2) Off-site: Sedimentation Pollution (eutrophication, etc)

From D. Pimentel et al. 1995, SCIENCE, Vol.267:1117-1123: Of the 75 billion tons of soil eroded worldwide each year, about two-thirds come from agricultural land. If we assume a cost of $3 per ton of soil for nutrients, $2 per ton for water loss, and $3 per ton for off-site impacts, this massive soil loss costs the world about $400 billion per year, or about $67 per person per year.

So, “soil erosion is everybody's business."

Rates of soil erosion?

• Soil erosion is a natural process that averages a loss of 0.2 tons per acre annually.
• The average annual rate of loss is 0.5 tons per acre for managed forests.
• The rate is 1.5 to 20 tons per acre for pasture and cultivated land.
• For unprotected construction sites the rate may jumps to 150 to 200 tons per acre.