Lecture 5-1 Flashcards
What does slope erosion by water include?
Entrainment, transport, and deposition of sediment
Processes- Rain splash, sheet erosion, Rill and gully erosion
What are the forces involved in hillslope erosion?
Erosion = Driving force/resisting force
Or E=Tractive force/material strength
Tractive force depends on Depth of overland flow and slope of the ground surface
Material strength = cohesion and particle size
What is rain splash erosion?
Soil erosion caused by direct impact of falling raindrops on slope surface.
effective in areas with sparse or no veg cover
-Amount of erosion depends on kinetic energy (drop size and wind speed) and slope angle
What is sheet erosion?
Erosion as a result of sheet flow- overland flow that froms a thin layer of water over a smooth surface
depends on slope angle and water depth
-transports eroded material prepared by splash erosion
What is rill erosion?
Erosion process along small channels called rills
- develop along the slope
- Rill density declines with slope length and steepness
- amount of eroded material depends on slope angle, water depth, and soil erodability
What is gully erosion?
Gullies: deep V-shaped channels carved by newly formed streams in rapid headward growth during advanced stages of accelerated slope erosion
- develop due to surface and subsurface flow
- develop in all climates
What is Colluvium?
When soil particles reach the base of a slope, they accumulate in a layer of debris
What is alluvium?
Any stream laid deposit (alluvial fans)
What is denudation?
Amount of sediment eroded from the basin.
- assumes sediment is completely removed from basin
- Assumes equal lowering of the surface over the entire basin area
- estimated as total volume of sediment divided by total basin area
what is sediment yield?
Amount of sediment eroded from the basin per unit basin area per unit time.
What are 5 controlling factors of sediment yield?
- Climate and vegetation
- basin size
- Elevation and relief
- Rock type
- Land-use and human activity
What role does vegetation play?
VEg and organic matter (litter) protects surface from erosion and raindrops. preserves cohesion in aggregated-clay soil.
rootlets bind soil together, inhibits free flow of water and reduces overland flow velocities
How does Basin size influence sediment yield?
Small basins have steep valley-side slopes. Small, steep basins may exhibit significant mass movements.
High drainage densities in upland areas
increased storage along floodplain of large basins
