Transcript Soil Erosion

Nancy Rogel
Eddie Guadarrama
● What is Soil Erosion
● Types of Erosion
● Factors Affecting Erosion Rates
● Human Activities that increase Erosion Rates
● How to Prevent Erosion
● In agriculture, erosion refers to the removal of
a field’s topsoil due to natural forces of water
and wind or through human activities such as
tillage
● 3 steps
o
o
o
Soil detachment
Movement
Deposition
● Water
○ Splash
○ Sheet
○ Rill
○ Gully
○ Bank
● Wind
○ Suspension
○ Saltation
○ Soil Creep
● Glacial
○ Plucking
○ Abrasion
○ Freeze-thaw
● Splash Erosion: Direct movement of soil by the impact of water droplets.
Soil particles can be thrown up to 3 feet
● Sheet Erosion: Uniform removal of soil in thin layers from a large area due to
impact from raindrops
● Rill Erosion: Small channels (<30 cm) carved out on a slope by running
water
● Gully Erosion: Large channels (>30 cm) carved out by running water that
cannot be removed by normal tillage equipment
● Bank Erosion: Saturated sides of running streams fall into moving water
below
Source: http://www.cep.unep.org/pubs/Techreports/tr41en/Image11.gif
● Suspension: The movement of fine particles into the atmosphere
over long distances due to strong winds
● Saltation: The movement of soil particles through short bounces
along the surface, displacing additional particles with each
impact. Primary source of wind erosion.
● Soil Creep: The rolling of larger soil particles across the surface,
aided by the bouncing movements of saltating particles
Source: http://passel.unl.edu/Image/siteImages/Saltationscreencapture2-LG.gif
• Plucking: Glacial ice freezes into cracks in rocks and when the
glacier moves it pulls out rocks leaving a jagged surface
•
•
Abrasion: When rock frozen to the base and the back of the
glacier scrapes the bed rock
Freeze-thaw: When water in the cracks of rocks freezes and
expands. Over time, portions of rock are broken off
● Climatic Factors
● Vegetation
● Characteristics of Soil
● Topography
o Rainfall
o Amount, Intensity and Frequency:
o A greater percentage of the rainfall will become runoff
during periods of frequent rainfall.
o This is due to high soil moisture or saturated conditions.
● Temperature:
o Frozen soil is
resistant to erosion
o Temperature affects
organic matter
● Important physical factor influencing soil erosion.
● Vegetation binds the soil together which makes it more resistant
to runoff.
● Organic matter is provided by vegetation which can slow down
runoff.
● A dense, robust cover of vegetation is one of the best protections
against soil erosion.
● Soil Texture:
o The size or combination of sizes of individual soil particles.
o Silt particles are most susceptible
o Clay or Sand particles are less prone to erosion.
● Soil Structure:
o Soil particles get
clumped together
to form larger
clumps and pore
spaces.
o Structure
influences both the
ability to absorb
water and its
resistance to
erosion.
● Slope Length:
o Longer Slope
o Base of the slope
● Slope Steepness & Surface
Roughness:
o Speed of runoff flow
o Erosion rates increase if the
flow is fast.
● Overgrazing
● Overcropping
● Deforestation
● Construction
● Occurs when plants are exposed to intese grazing.
● Animals can damage the soil surface by eating the vegetation and
compacting dry soil with their hooves.
● Soils with less vegetation become exposed and are more prone to water
and wind erosion.
● This occurs when the land is being continuously cultivated with no
breaks in between crops.
● Humus Production is affected
● The soil dries out and is prone for wind and rain erosion with less
humus.
● Deforestation leaves an open and exposed landscape after cutting down
large areas of forests.
● Nutrients and minerals are removed from the soil
● Areas are exposed to water and wind erosion.
● Construction often begins with by clearing the area of any plants or
other natural defenses against soil erosion.
● Construction also includes several tasks such as altering drainage
patterns and compacting the soil.
● Terracing
o A sloped plane is cut into a series of successively receding flat surfaces
● Contour Farming
o Planes of land are constructed by cutting off the land according to its
contours.
● Cover crops
● Windbreaks
o Plant trees and shrubs along the edges of agricultural fields to help protect the
fields against wind erosion.
● Mixed-cropping
● Crop rotation
http://www.kalkaskacounty.net/planningeduc0043.asp
http://en.wikipedia.org/wiki/Erosion#Factors_affecting_erosion_rates
http://lcgeography.preswex.ie/how-human-activities-can-accelerate-soil-erosion.html
http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0003/255153/fact-sheet-1-types-of-erosion.pdf
http://passel.unl.edu/pages/informationmodule.php?idinformationmodule=1086025423&topicorder=19&maxto=7
http://www.geography.learnontheinternet.co.uk/topics/glaciation1.html