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Factors affecting Discharge
Physical
· Weather
­ Snow ­ melt, frozen ground no infiltration
­ Precipitation ­ heavy rainfall
­ Temperature ­ evapotranspiration (reduce discharge)
· Drainage Basin
­ size ­ rounder quicker
­ shape ­ Smaller responds more rapidly
­ Slope ­ steep, water reaches more quickly
· Vegetation ­ more trees less infiltration
· Porus soil type/permeable rock - slow
· Impermeable rock ­ faster
Human
· Urbanisation ­ permeable structures, artificial drainage, machinery
· Land use ­ dams, agriculture
· Deforestation…read more

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Long profile & River processes
Erosion Vertical
· Hydraulic Action ­ water compresses air making · Cuts down to base level leaving steep sided
small explosion valleys by the processes of abrasion and
· Abrasion ­ Wearing away of rocks by the river hydraulic action
· Attrition ­ Wearing away of rocks from the Lateral
other rocks · Energy used in widening the valley by
· Corrosion ­ Rocks are dissolved hydraulic action erosion
Transportation Capacity
· Traction ­ Large boulders rolled along river bed · Amount of material it can carry
· Saltation ­ small stones bounce and leapfrog Competence
· Suspension ­ Sand/Silt picked up and carried ­ · Diameter of the largest particle that it can
brown colour carry for a given velocity
· Solution ­ Minerals transported within the
water
Deposition
· Discharge reduced
· Shallow water
· Increased size of load (tributary)
· River floods…read more

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Factors affecting Load
(material transported)
· Climate /seasonal variations
· Land use - deforestation
· Precipitation ­ more water more velocity
· Vegetation cover
· Reservoirs
· Geology ­ some may be dissolved
· Runoff
· Soil properties
· Topography ­ relief ­height and shape of land
· Size of basin…read more

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Valley profiles
Channel cross profiles Cross Profile
· View from side ·View of a valley from one side
· Changes throughout ­ Up, narrow and uneven ­ ·Lower course ­ Very wide, Lack
Mid, meanders ­ Low, widen and deepens of erosion, reduced competence
·Middle course ­ Wider, lateral
· Upper ­ large wetted perimeter more friction
erosion
· Higher the hydraulic radius more efficient channel ·Upper course ­ Narrow steep
Potential and kinetic energy sided, vertical erosion
· Determined by volume (discharge) and gradient ­ Long profile
increase = increase kinetic ·Knick points ­ rejuvenation
· Processes depend on this ·Change in altitude
· Excess = erosion, insufficient = deposition ·Steeper upper course ­ gentle
at mouth
Graded Profile
·Irregularities ­ rapids,
· Inputs should balance outputs ­ changes in system waterfalls
= change in profile
· Graded river ­ all energy used so no further erosion
· Profile of dynamic equilibrium ­ balance between
erosion and deposition
· Overtime river decrease in gradient ­ smooth
concave shape, adjusted discharge and load…read more

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Rejuvenation & Knick points
Rejuvenation ­ increase in energy
Cause
· Isostatic ­ Rise and fall of land
· Eustastatic ­Change in sea level
Knick points
· River gains cutting power ­ vertical erosion
· Adjustment to new base level
· Knick point ­ where old long profile meets new
· Recedes upstream…read more

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