water soil erosion Flashcards
what is soil quality?
the capacity of a soil to function in its ecosystem boundaries, sustain biological diversity, maintain environmental quality, promote plant/ animal health
when does degradation occur?
when the soil quality is reduced
what is soil erosion?
detachment and transport of soil or rock particles largely due to wind and water, not same as weathering, erosion involves movement
what is weathering?
breakdown of rock through non-movement processes
what is splash erosion?
occurs when rain drops hit bare soil, detachment on impact, impact breaks up soil, splashed particles can rise 60cm and up to 1.5m, extremely local effects.
it causes a crust to form as splashed particles fill spaces increasing run off reducing infiltration, drop size increases with rainfall intensity
what is interill erosion?
water ponds on the surface, fraction of rainfall not infiltrating will overland flow,.
may be for two reasons, rain arrives too quickly (hortonian flow), or if soil is fully saturated and can no longer hold (Hewlett type), water moves downslope thin film little energy, irregular surface creates ponding, detachment by raindrops decreases as surface water depth increases
what is rill erosion?
rain continues increasing water overtops depressions, interill stops, greater volume more kinetic energy on overland flows, more soil can be detached
how does rill development occur?
lowered areas of land form preferential paths for flow more erosion occurs, +ve feedback results in small linear concentrations of overland flow, some microrills get filled by sedimentation, some are eroded more
what occurs in rill networks?
competition between micro rills and rills leads to self organised erosional channels, efficient pathways for hillslope water removal, =
what is rill erosion?
most dominant form of water erosion, it occurs in rainier months common in bare agricultural land
what is gully erosion?
long duration or high intensity rainfall events, runoff continues to accelerate and small subset of rills grow into gullies, they are defined as channels deeper than 30cm more soil is lost through interill or rill erosion
erosion by water which scales does it occur?
it occurs over lots of spatial scales, (splash and interrill erosion occurs at mm), (rill erosion occurs at Meters) and (gully erosion occurs at hundreds of M)
