Vincent Raeburn Linlithgow AcademyMalcolm McDonald Bathgate Academy Linlithgow Academy
How rivers erode
HYDRAULIC ACTION The force of the water weakens and breaks up the rocks
ABRASION The material carried in the river wears away the river bed
ATTRITION As the pebbles carried by the river crash into each other,they become smaller and rounder
SOLUTION The water in the river dissolves the minerals in the rocks
How rivers transport
Rolling stones along the river bed.( needs lots of energy)
Traction
SuspensionClay sized particles are carried
along by the river flow
SaltationSand sized particlesbounce along the riverbed
SolutionSome minerals are
dissolved by the riverwater
river flow
River BasinSource of River Aye
Confluenceof River Ayeand tributary
Tributaryof River Aye
Flood plain
Mouth ofRiver Aye
Sea
Estuary ofRiver Aye
Watershed of River Aye(boundary between basins)
Sourceof river
UpperCourse
MiddleCourse
LowerCourse
FEATURES OF THE UPPER COURSE
V-SHAPED VALLEYS WITH INTERLOCKING SPURS
POT HOLES ON RIVER BED
WATERFALLS AND RAPIDS
Formation of a waterfall
Soft rock
Hard rock
Steep sides( gorge )
Vertical erosionForms plunge pool
Undercuttingerodes the softer rockforming an overhang
The overhangEventuallycollapses
The processstarts again
Eroded rock
WaterfallRetreats upstream
PLUNGE POOLUNDERCUTTIN
G OF SOFT ROCK
OVERHANG
WATERFALL RETREATS . .UPSTREAM . .
The River Avon has smoothed off partsof this hard igneous rock. . .
What is this process called?
MEANDERS
Flood plain
Meanders
© Used with the permission of the Geological Survey of Canada, Natural Resources Canada
Available at http://sts.gsc.nrcan.gc.ca – Terrain Science Division
Most erosionon the outsideof the bend .. Fastest flow
Possible breakthrough point
Possible ox-bowlake
Fastest current slowest current
Outer bankIs undercut
Slip off slope( river beach )Deposition ofSand and shingleDeepest part
of the river
Bank willcollapse
Small rivercliff
River bend
Formation of an ox-bow lake
The meanders change shapethrough time
At the bends the river flows faster at the outside
The bends migrate Sideways leaving deposits on the insideOf the bend
The erosion makes the Meanders more pronounced
Small river cliff is formed
Most erosion
Most deposition(Slip off slope)
Some bends get closerand closer
The neck gets narrower and narrower
Eventually during a period of heavy river flow it cuts through
The river now follows the new route
The old meanderIs left as a small lake(OX - BOW lake)
© Used with the permission of the Geological Survey of Canada, Natural Resources Canada
Available at http://sts.gsc.nrcan.gc.ca – Terrain Science Division
Want to see that again ?
NARROW MEANDER NECK
FUTUREOX-BOW LAKE
Gentle valley sides
Flat floodplain
Layers of siltDeposited during floods
Coarse materialForms naturallevees
River is actually flowing aboveThe floodplain !!
Levees is oftenartificiallystrengthened
Characteristics Upper Course Middle CourseLower Course
Slope
Width
Depth
StraightnessLoad
Main work
Valley width
Type of load
usually steep
narrow
shallow
winding
little
large/small angular
erosiontransportation
quite steep
quite wide
quite deep
meandering
some
medium/smallrounded
Transportation
narrow
gentle
quite wide
wide
deep
big meanderslots
small+rounded
transportationdeposition
wide
Reproduced with kind permission of Ordnance Survey © Crown Copyright NC/03/18990
tributaries
ox-bowlake
meander
V shaped valley
SteepValleysides
Floodplain
