water erosion
DESCRIPTION
Water Erosion. “It is the detachment, transportation & deposition of soil particles by the force of water from one place to another.” “It is the movement of soil by rain water including melted snow, running rapidly over exposed land surfaces.”. Factors Affecting Water Erosion. 1. Climate. - PowerPoint PPT PresentationTRANSCRIPT
Water Erosion
“It is the detachment, transportation & deposition of soil particles by the force of water from one place to another.”
“It is the movement of soil by rain water including melted snow, running rapidly over exposed land surfaces.”
Factors Affecting Water Erosion
1. Climate.
Precipitation Temperature Wind Humidity Solar radiation
2. Soil
Physical properties of soil such as texture, structure etc.
Organic matter contents in soil. Moisture contents in soil. Soil density or compactness. Chemical and biological characteristics.
3. Vegetation
Reduce rain drop velocity. Resist runoff Increase infiltration Enhance microbial activity. Improve soil structure.
4. Topography.
Degree of slope of an area Length of slope of an area Size and shape of water shed
Forms of Water ErosionForms of Water Erosion
Raindrop or Splash Erosion:Raindrop or Splash Erosion: Result from the impact of water drop directly on the Result from the impact of water drop directly on the
soil particles or thin water surfaces.soil particles or thin water surfaces. Splash losses are 50-90 times greater than the wash Splash losses are 50-90 times greater than the wash
off losses.off losses. On bare soil 224 Mg haOn bare soil 224 Mg ha-1-1 is splashed into air due to is splashed into air due to
heavy rains. heavy rains. It is first stage of water erosion. It is first stage of water erosion. Raindrops can be a major problem for farmers when Raindrops can be a major problem for farmers when
they strike bare soil. they strike bare soil. Soil particles can jump up to 2.5 feet.Soil particles can jump up to 2.5 feet.
The relationship between erosion and rainfall momentous and energy is determined by
i. Rain drop size
ii. Mass
iii. Size distribution
iv. Shape
v. Velocity
vi. Direction
Energy equation has been developed by Wischmerer & Smith (1958) is:
E = 12.1 + 8.9 log i
E = Kinetic energy in Mg ha-1
i = intensity in mm h-1
Factors affecting direction & distance of soil splash are:
i. Shape
ii. Wind
iii. Surface condition
Raindrop ErosionRaindrop Erosion
Sheet Erosion Sheet Erosion
Uniform removal of soil in thin layers from sloping Uniform removal of soil in thin layers from sloping land.land.
Occurrence is rare.Occurrence is rare. In reality the loose soil merely runs off with the rain.In reality the loose soil merely runs off with the rain. The beating action of raindrops combined with The beating action of raindrops combined with
surface flow causes initial microscopic rilling.surface flow causes initial microscopic rilling. From energy point of view, raindrop erosion is more From energy point of view, raindrop erosion is more
important because raindrops have velocities of 6-9 important because raindrops have velocities of 6-9 msms-1-1 (20-30 fs (20-30 fs-1-1) whereas overloaded flow velocities ) whereas overloaded flow velocities are about 0.3-0.6 msare about 0.3-0.6 ms-1-1 (1-2fs (1-2fs-1-1).).
Sheet ErosionSheet Erosion
Rill ErosionRill Erosion
Transitional phase between sheet erosion and Transitional phase between sheet erosion and gully erosion gully erosion
Its effects can be easily removed by tillageIts effects can be easily removed by tillage It occurs when soil is removed by water from It occurs when soil is removed by water from
little streamlets that run through land with little streamlets that run through land with poor surface drainingpoor surface draining
Rills can often be found in between crop rows Rills can often be found in between crop rows
Rill ErosionRill Erosion
Gully ErosionGully Erosion
It is last stage of water erosion. It is last stage of water erosion. Gullies are larger than rills and cannot be fixed by Gullies are larger than rills and cannot be fixed by
tillage.tillage. Gully erosion is an advanced stage of rill erosion.Gully erosion is an advanced stage of rill erosion. Major concentrations of high-velocity run-off water Major concentrations of high-velocity run-off water
in these larger rills remove vast amounts of soil.in these larger rills remove vast amounts of soil. This results in deeply incised gullies occurring along This results in deeply incised gullies occurring along
depressions and drainage lines.depressions and drainage lines.
Gully ErosionGully Erosion
Stream Erosion.Stream Erosion.
When water flow in gullies become When water flow in gullies become permanent, it is called a stream which may be permanent, it is called a stream which may be permanent or seasonal is called as stream permanent or seasonal is called as stream
erosionerosion..
Areas of Water Erosion
Nothern Hilly Areas Pothwar Pleatue Foothills of Himalayas in Punjab Western hilly Areas
Damages of Water Erosion
Loss of soil specially fertile layer Low fertile soil decrease farmer income Remove organic matter from the soil Decrease infiltration capacity of soil Increase runoff Increase flood hazard Damage the wild life fisheries etc Fill up the streams and dams
Mechanism of Water ErosionMechanism of Water Erosion
A. A. DetachmentDetachment.:.: it is first to occur and is it is first to occur and is independent variable. Soil clods are broken independent variable. Soil clods are broken into small particles.into small particles.
B.B. Transportation Transportation.:.: it is dependent variable and it is dependent variable and depends upon detachment.depends upon detachment.
C.C. Deposition Deposition:: is dependent variable and depend is dependent variable and depend upon detachment and transportation.upon detachment and transportation.