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Geography - River valley and processes - Coggle Diagram
Geography - River valley and processes
The River Valley
Drainage basin
area of land drained by a river and its tributaries
Long Profile
change in gradient downstream
steep upper course
gently sloping middle course
flat lower course
Cross Profile
shape of valley from one side to other
Channel
wider and deeper
Valley
wider and flatter
Upper course
Steep gradient
V-shaped valley
steep sides
narrow, shallow channel
Boulders and rocks
Vertical erosion
lots of tributaries
turbulent velocity
Middle course
U shaped valley
gently sloping sides
Vertical + Lateral erosion
Smoother stones + pebbles
abrasion + attrition
rounder, deeper channel
Medium gradient
more energy
Lower course
Very wide, flat valley
very wide, deep channel
Gentle gradient
Smooth silt
Lateral erosion
fast flowing
Water velocity
speed dependant on course
Friction
water and riverbed
slows water
more contact
more friction
slower
Upper Course
shallow channel
water passes riverbed
friction
slows
Lower course
faster flowing
less friction
finer sediment
River Processes
Erosion
Hydraulic Action
Force of water collides with rocks and breaks away from channel
Abrasion
Bed load carried by river scrape/rub against channel
Attrition
Rocks carried by river knock against each other
smaller and more rounded
Solution
alkaline rocks dissolved by slightly acidic water
dominant in upper course
Transportation
Traction
Large pebbles roll along river bed
Suspension
Small particles carried by river
Saltation
Bouncing of pebbles along river bed
Solution
Dissolved load carried along
Deposition
river drops material
when river velocity decreases and loses energy
Larger rocks deposited in upper course
heavier
Smaller sediment carried downstream
deposited on bed or bank
velocity decreases due to friction
mouth
mudflats
dominant in lower course
Factors affecting erosion
Gradient
steep gradient
more energy
more erosion
Amount of bed load
lots of rocks
abrasion increases
Concrete river banks
reduce lateral erosion
Human factors
changing landscape
remove vegetation
decrease time for rainfall to get to river
increase volume and energy