SOIL EROSION Nancy RogelEddie Guadarrama

OUTLINE● What is Soil Erosion

● Types of Erosion

● Factors Affecting Erosion Rates

● Human Activities that increase Erosion Rates

● How to Prevent Erosion

WHAT IS SOIL 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 stepso Soil detachmento Movemento Deposition

TYPES OF EROSION● Water

○ Splash○ Sheet○ Rill○ Gully○ Bank

● Wind○ Suspension○ Saltation○ Soil Creep

● Glacial○ Plucking○ Abrasion○ Freeze-thaw

WATER EROSION ● 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

WIND EROSION● 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

GLACIAL EROSION• 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

FACTORS AFFECTING EROSION RATES● Climatic Factors

● Vegetation

● Characteristics of Soil

● Topography

CLIMATIC FACTORSo Rainfallo 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.

CLIMATIC FACTORS● Temperature:

o Frozen soil is resistant to erosion

o Temperature affects organic matter

VEGETATION● 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.

CHARACTERISTICS OF SOIL● 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.

CHARACTERISTICS OF SOIL● 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.

TOPOGRAPHY● Slope Length:

o Longer Slopeo Base of the slope

● Slope Steepness & Surface Roughness:o Speed of runoff flow o Erosion rates increase if

the flow is fast.

HUMAN ACTIVITIES THAT INCREASE EROSION RATES

● Overgrazing

● Overcropping

● Deforestation

● Construction

OVERGRAZING● 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.

OVERCROPPING● 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● 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 ● 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.

HOW TO PREVENT EROSION● Terracing

o A sloped plane is cut into a series of successively receding flat surfaces

● Contour Farmingo Planes of land are constructed by cutting off the land according to its

contours.

● Cover crops

● Windbreakso Plant trees and shrubs along the edges of agricultural fields to help

protect the fields against wind erosion.

● Mixed-cropping

● Crop rotation

WORK CITEDhttp://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