Chapter 3 Soil Erosion and Its Controls

1
Chapter 3 Soil Erosion and Its Controls

2
3.1 Introduction

• Soil erosion is the detachment and removal of
  soil particles from the soil mass by water or
  wind.

3
3.1 Introduction

• Geologic erosion is the erosion under natural or
  undisturbed condition. It is called normal
  erosion or natural erosion also.
• Accelerated erosion is the increased rate of
  erosion over the geologic erosion brought about
  by humans activity.

4
3.1 Introduction

• Soil erosion rate is the gross amount of soil
  moved by water and wind.
• Soil loss is the soil moved off a particular
  slope or field.
• Sediment yield is soil loss delivered to a point
  under evaluation.
• Kirkby, M.J. and R.P.C. Morgan. Edited. Soil
  Erosion, John Wiley Sons.

5
3.1 Introduction

• Classification of erosion by eroding agents
• Water erosion
• Wind erosion

6
3.1 Introduction

• Classification of erosion by action
• Rain drops
• Shallow flows
• Concentrated flows

7
3.1 Introduction

• Classification of erosion by form
• Sheet erosion
• Rill erosion
• Gully erosion
• Channel erosion

8
3.1 Introduction

• Classification of erosion by location
• Inter-rill erosion
• Rill erosion

9
General classification of erosion
Inter-rill erosion Rill erosion Gully
erosion Channel erosion

• Water
• Wind
• Gravity
• Freezing and thawing erosion

Mass movement
10
3.2 Factors affecting erosion

• Climate R
• Soil K
• Topography LS
• Biological B
• Engineering E
• Tillage T

11
3.3 Measurement of soil erosion

• Microplots 1cm2
• Unit plot 6ft?72.6ft 0.01 acre
• Large plots
• Small watersheds
• lt1000 km2
• lt200 km2
• lt50km2
• Hydrological stations

12
3.4 Prediction of soil loss

• Scientific farm planning for soil and water
  conservation requires knowledge of the relations
  between those factors that cause loss of soil and
  water and those that help reduce such losses.
• Controlled studies on field plots and small
  watershed have supplied much valuable information.

13
3.4 Prediction of soil loss

• Greatest benefits from such research can be
  realized only when the finding are converted to
  sound practice.
• Specific guidelines are needed fro selecting the
  control practices.
• The soil loss prediction procedure provides such
  guidelines.

14
3.5 Soil Loss Tolerances

• The maximum level of soil erosion that
  will permit a high level of crop productivity to
  be sustained economically and indefinitely

15
3.6 Models of soil erosion

• 1940, Zigg, A.W., Degree and length of land slope
  as it effects soil loss I runoff
• 1965, Wischmeier, W.W., Universal soil loss
  equation
• 1978, USLE
• 1980, CREAMSChemicals, Runoff, and Erosion from
  Agricultural Management Systems
• 1996, WEPPWater Erosion Prediction Project
• 1997, RUSLERevised Universal Soil Loss Equation