Soil erosion is the detachment and transportation of soil particles
by the forces of water and/or wind.It is a process that transforms soil into sediment.Sediment
consists of transported and deposited particles or aggregates
derived from rock, soil, or biological material.
erosion is a natural process
that wears down topographic highs (hills and mountains) and
fills in topographic lows (valleys, lakes, and bays) through the
deposition of eroded sediments.
Examine a landscape formed erosion website
(or solution) – water is capable of dissolving
that exceeds normal geologic erosion becomes destructive and is
called accelerated erosion.This
type of erosion occurs when the soil and natural vegetation are
disturbed by human activity.Accelerated erosion is often 10 to 1000 times as
destructive as geological erosion.
Soils Susceptible to Erosion
that are susceptible to erosion include:
soils with low water infiltration capability
soils with low organic matter content
soils with poor (unstable) structure
soils on steep hills (especially in regions of
soils with hydrophobic characteristics (usually
intensified by fire)
Effects/Consequences of Soil Erosion
Soil erosion causes two main problems:
of soil productivity: When topsoil erodes, the less fertile
and harder B horizon becomes exposed.This leads to lower forage production, lower water
infiltration and greater runoff.
pollution: when eroded sediment is rich in fertilizers or
pesticides, it can upset the ecosystem at its point of
addition, sediments may damage machinery, agitate respiratory
problems and reduce visibility.
3.2 Water Erosion
are three steps to accelerated erosion by water:
or loosening of soil
particles caused by flowing water, freezing and thawing of the
topsoil, and/or the impact of falling raindrops.
of soil particles by floating, rolling, dragging, and/or
of transported particlesat
some place lower in elevation.
detachment, transportation, deposition
The three-step process of soil erosion by water starts with the impact of raindrops on soil.
the translocation of soil through the process of splashing.Individual
raindrops detach soil aggregates and redeposit particles.The dispersed particles may then plug soil pores,
reducing water intake.Once
the soil dries, these particles develop into a crust at the soil
surface and runoff is further increased.
The splash that results when the drop strikes a wet, bare soil
Universal Soil Loss Equation (USLE) was originally developed to estimate sheet and rill erosion losses from cultivated fields in
the United States.It is now also
applied to regions outside the US, and to rangelands and to forestlands.The equation is used to show how different soil and
management factors influence soil erosion.
A = R K LS C P
Predicted soil loss due to water erosion
Results in t/acre/year or t/ha/yr
Quantifies the erosive force of rainfall and runoff.It takes into account both total amount of rainfall
and its intensity.
Soil erodibility factor
Represents the ease with which a soil is eroded.It quantifies the cohesiveness of a soil and its
resistance to detachment and transport.
Slope length and steepness factor
It is the ratio between the plot in question and a
standard unit plot.Steeper
slopes lead to higher flow velocities; longer plots
accumulate runoff from larger areas and thus also result
in higher flow velocities.
Vegetative cover and management factor
Considers the type and density of vegetative cover as well
as all related management practices such as tillage,
fertilization, and irrigation.This is the most complicated factor to calculate.
Erosion control practices factor
Influence of conservation practices such as contour
planting, strip cropping, grassed waterways, and terracing
relative to the erosion potential of simple up-down slope
3.3 Wind Erosion
erosion occurs where soil is exposed to the dislodging force of
of wind erosionvaries
with surface roughness, slope, type of cover on the soil
surface, and wind velocity, duration, and angle of incidence.Fine soil particles can be carried to great heights and
for hundreds of kilometers.
video clips illustrate transportation of sand particles by wind:
SAND MOVEMENT; from Kansas State University, the MPG movie
shows wind tunnel sediments moving through creep, saltation,
SAND MOVEMENT CLOSE UP; from Kansas State University, a
close up of video 6 above, the MPG movie shows sediments
moving in the form of creep, saltation, and suspension in a
wind tunnel. (end of new addition)