Lecture 1 Flashcards
What is detachment?
separation of soil particle from soil mass.
What is entrainment?
Transport of detach particles from the soil surface to a fluid flow. (wind, water, ice).
Transport
Transportation of sediment
Disposition
transfer of sediment from the sediment lobe to the soil surface.
Definition of shear stress
Shear stress is when the direction of stress/force is parallel to the affected surface as opposed to perpendicular
Small impoundments
Reduce sediment movement from landscape.
Occurs naturally and constructed.
Almost no transport capacity
What can reduce the erosivity of wind?
Vegetation cover, surface roughness reduce erosivity
Three modes of wind transportation
1 creep
2 Saltation
3 suspension
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Infiltration capacity
Soils capacity to hold water
Material strength
resistance to stress
Types of erosion differentiated on the basis of:
- Location (hillslope, channel erosion)
* Agent (water, wind(deflation), ice(glacier erosion is called denudation)
What cases soil aggregation?
Attractive forces among soil particles, (some particles binds stronger than other, the space between aggregate creates pore space for air or water)
Soil permeability
Is a measure indicating the capacity of the soil to allow fluids to pass through it.
Erosivity
Erosivity is the term used to describe the potential of raindrop impact, runoff from snowmelt, or water applied with an irrigation system rainstorm to detach and erode soil.
Temporal and spatial variability
Wetting, drying, freezing, thawing, addition of organic matter
Primary factors that influences soil erosin
1 Climate
2 Topography
3 Land use and landcover
Erodibility
The susceptibility of the ground(soil) surface to erosion.
Erosivity isn’t always directly related to rainfall amount, aspects to consider
- Spatial variation
- Temporal variation
water erosion consist of 3 processes
1 detachment
2 transport
3 deposition
How to classify soil erosion?
You can classify by agent causing erosion –> water, wind
Wind abrasion
the impact of particles carried by the wind. The wind picks up particles and moves them. When the particles collide with a solid object, the impact causes small pieces of the object to break off.
The three processes of wind erosion
creep,
saltation
suspension.
Mechanical movement of soil
Tillage – Tillage lift soil layer, gravity cases downslope movement.
Mass movement – rainfall saturates (mättar) the upper soil layer and reduce soil strength.
Deposition occurs when and where…
the sediment load si greater than the wind’s capacity
Interill + rill areas = overland flow areas of landscape, caused by:
Hortonian flow/Horton overland flow which is infiltration capacity + depression storage capacity.
Open channels
An open channel has free-water surface exposed to atmospheric pressure. Open channels occurs in in rills, streams and gully’s.
Pipe flow
Pipe flow fills the conduit with water that flows under the hydraulic pressure. (water frequently flows through the soil just below the surface. The soil may contain macropores, other small openings and channels left by for example decaying roots, burrowing insects and animals. These internal open spaces in the soil may become pipes, and pipe flow can erode flow, causing a type of erosion know as piping.
Sheet erosion
Sheet erosion occurs as a shallow ‘sheet’ of water flowing over the ground surface, which is a uniform to remove removal of soil from surface, is assumed to be the first phase of the erosion process.
Catchment sediment yield
= the amount of sediment delivered at the outlet of the catchment
irrigation
Irrigation water is applied to the land by overhead by sprinklers or small pipes, surface applied flow.
Does all drops move sediment?
No if it’s already water on the ground that’s 3 times deeper than the size of the drop there is no impact.
Small impoundments (reservoirs)
Reduce sediment movement from landscape
Natural and constructed
Almost no sediment transport
