Water erosionWater erosion

Water wears a path as Water wears a path as

it travels down a slope it travels down a slope

Kind of water erosionKind of water erosion

Water erosion

Rill erosion Gully erosion Sheet erosionStream erosion

Rill erosionRill erosion

• Have you ever seen a scar or small Have you ever seen a scar or small channel on the side of a slope that channel on the side of a slope that waswas

left behind by running water? That is left behind by running water? That is evidence of rill erosionevidence of rill erosion

An erosion process in which many An erosion process in which many small channels a few centimetres small channels a few centimetres deep are formed; it occurs mainly on deep are formed; it occurs mainly on recently cultivated soils. See also rill. recently cultivated soils. See also rill.

• Rill erosion is the most common form Rill erosion is the most common form of erosion. of erosion.

• Its effects can be easily removed by Its effects can be easily removed by tillagetillage, it is the most often overlooked. , it is the most often overlooked. It occurs when soil is removed by water It occurs when soil is removed by water from little streamlets that run through from little streamlets that run through land with poor surface draining. land with poor surface draining.

• Rills can often be found in between Rills can often be found in between crop rows. crop rows.

Rill Erosion pictureRill Erosion picture

Gully pictureGully picture

Gully erosionGully erosion

• It is a rill erosion channel becomes It is a rill erosion channel becomes broader and deeperbroader and deeper

• Gullies are larger than rills and Gullies are larger than rills and cannot be fixed by cannot be fixed by tillagetillage. Gully . Gully erosion is an advanced stage of erosion is an advanced stage of rill erosionrill erosion, just as rills are often the , just as rills are often the result of result of sheet erosionsheet erosion

Question-1Question-1

What is Tillage?What is Tillage? Tillage practices are used for wind erosion control Tillage practices are used for wind erosion control

by producing a rough, cloddy surface that by producing a rough, cloddy surface that maintains surface residue and conserves soil maintains surface residue and conserves soil moisture. When used along with crop residues, moisture. When used along with crop residues, also known as stubble mulch tillage, reduced also known as stubble mulch tillage, reduced tillage, or conservation tillage, it reduces wind tillage, or conservation tillage, it reduces wind velocity and traps eroding soil. velocity and traps eroding soil.

Tillage is also very effective in controlling rill and Tillage is also very effective in controlling rill and sheet erosion. The rough surface along with crop sheet erosion. The rough surface along with crop residues prevents rain water from carrying of soil residues prevents rain water from carrying of soil particles and other organic matter. particles and other organic matter.

Stream ErosionStream Erosion

• Some times water continues to flow along a Some times water continues to flow along a depression it has created. It becomes a depression it has created. It becomes a stream like the one shownstream like the one shown

Picture – Steam erosionPicture – Steam erosion

• It constantly picks up sediments It constantly picks up sediments from the bottom and sides of its from the bottom and sides of its channel. Water picks  up and channel. Water picks  up and carries some of the lightweight carries some of the lightweight sediments, while large, heavy sediments, while large, heavy particles just roll along the particles just roll along the bottom of the stream channel. bottom of the stream channel. All of these difference-sized All of these difference-sized materials scrape against the materials scrape against the bottom and sides of the cannel, bottom and sides of the cannel, where they continue to knock where they continue to knock loose more sediments. Because loose more sediments. Because of this a stream continually cuts of this a stream continually cuts a deeper and wider channel    a deeper and wider channel   

Stream pictureStream picture

Sheet ErosionSheet Erosion

• Sheet erosion is defined as the uniform removal Sheet erosion is defined as the uniform removal of soil in thin layers from sloping land.of soil in thin layers from sloping land.

• This, of course, is nearly impossible; in reality This, of course, is nearly impossible; in reality the loose soil merely runs off with the rain. the loose soil merely runs off with the rain.

• It is happens when rainwater flows into lower It is happens when rainwater flows into lower elevations, carrying sediments with itelevations, carrying sediments with it

• The water loses some of its energy of motion The water loses some of its energy of motion and it drains into the soil or slowly evaporatesand it drains into the soil or slowly evaporates

Sheet Erosion picture Sheet Erosion picture

DepositionDeposition

• Think about...Think about...• As water moves throughout a river system,As water moves throughout a river system,

What do you suppose happens as it loses What do you suppose happens as it loses some of its energy of motion?some of its energy of motion?  

The water can no longer carry some of its The water can no longer carry some of its sediments, and they are deposited.sediments, and they are deposited.

DepositionDeposition

• Some stream sediments aren’t Some stream sediments aren’t carried very far at all before they are carried very far at all before they are deposited.deposited.

• -Many sediments are deposited -Many sediments are deposited within the stream channel it selfwithin the stream channel it self-Other stream sediments travel great -Other stream sediments travel great distances before hey are deposited  distances before hey are deposited 

Type of DepositionType of Deposition

• There is two types of Deposition There is two types of Deposition

Alluvial fan:Alluvial fan:A triangular deposit A triangular deposit of sediment that of sediment that forms when water forms when water rushing down a rushing down a slope loses its slope loses its energy and abruptly energy and abruptly slows at the slows at the bottom, depositing bottom, depositing its sediment load.its sediment load.

Delta:Delta:A triangular deposit A triangular deposit of sediment that of sediment that forms when a forms when a stream or a river stream or a river slows as it empties slows as it empties into an ocean, gulf, into an ocean, gulf, or lake.or lake.