RIVERS
Research Review
FACTORS THAT AFFECT RIVER VOLUME
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Size of Drainage Basin
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large drainage basin= several tributaries= more
volume
Vegetation
heavy vegetation= < runoff= < volume
 Little vegetation= > runoff= > volume
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Climate
> precip= > volume
 < precip= < volume
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Permeability of Rock
> permeability = < runoff = < volume
 < permeability = > runoff = > volume
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FACTORS AFFECTING RIVER VELOCITY
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Discharge
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Gradient of the Land
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Steeper river channel = faster flow
Roughness of Channel
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> discharge = faster flow
Rough river bed = slower flow
Shape of Channel Cross Section
More water is in contact with riverbed = slower flow
 Faster in middle than on sides
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WAYS A RIVER CAN ERODE
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Abrasion/Corrasion
Rocks carried in the river grind/erode rocks
 Widens and deepens
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Hydraulic Action
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Attrition
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force of the water causes rocks to break
Material suspended in water collides w/ each other
and become smoother and rounder
Solution/Corrosion
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Water dissolves mineral in rocks and carries it away
HOW RIVER’S TRANSPORT A LOAD

Solution
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Suspension
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Light material that is suspended in the water and
carried in river (sand, silt, etc.)
Saltation
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Material dissolved in the water (minerals)
Gravel/small rocks lifted and carried small distances
and then dropped (related to river energy)
Traction
Movement of large boulders
 Requires lots of river energy (flood)
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UPPER COURSE

River Channel
Small and narrow
 Rough and shallow
 < volume
 < speed
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River Valley
Deep, narrow, and steep-sided
 V shaped valley
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UPPER COURSE FEATURES

Rapids
Occurs between soft and hard rock
 Hard rock does not erode as fast as soft rock
 Create areas of steep slope and less steep slope

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Waterfalls
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Sudden fall of water where water drops vertically
Plunge Pool

Dent in river bed at bottom of waterfall
MIDDLE COURSE

River Channel
Wider and deeper
 > volume
 < gradient than upper course
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River Valley
More open
 U shaped
 Wider river floor
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MEANDERS
Bends in river
 May go around tree or rock
 Water outside bend moves faster than inside
(more erosion outside)
 Sediment is deposited on inside of meander b/c of
slower velocity
 Deeper and more velocity outside
 Shallower and less velocity inside
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LOWER COURSE

River Channel
Deepest and widest
 Greatest volume
 Lowest speed
 Gentle gradient
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River Valley
broad
 Flat
 Bounded by bluffs
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LOWER COURSE FEATURES

Levees and Floodplains
Rivers slow and drop load which shallows river and
flat land decreases velocity
 Heavy rain causes river to overflow banks into plains
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Delta
Occurs at mouth of river where dumps into sea
 Slowing of rivers drops deposits

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Ox Bow Lake
Horse shoe shaped or crescent shaped
 Forms when deposits build on concave banks of
meander and become joined
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