Drainage Basins
A drainage basin is an area of land drained by a river and its tributaries.
Features of a drainage basin:
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Water shed - An area of high land which forms the edge of a river basin
Tributary - A small river flowing into a large river
Confluence - The point where two rivers meet
The source - Where a river starts
Mouth - Where a river flows into (lake or sea)
River Processes
The input to rivers in precipitation (rain, snow etc)
The processes of a river are: Erosion >>> Transport >>> Deposition
The outputs from rivers are physical features
How do rivers shape the landscape?
Below are ways that rivers change the landscape and a short description of each:
Hydraulic action: Force of water on river bank undercuts and removes material.
Corrasion: Rocks bounce against side and bottom of river and break off more material.
Attrition: Rocks collide with each other and break up into smaller pieces.
Solution: Dissolved material being carried along by the river.
Suspension: Small particles carried along by the river.
Traction: Particles carried along the river bed.
Saltation: Bedload particles bounced along the river bed.
Deposition: River slows and dumps material including silt.
The Upper Course
http://geobytesgcse.blogspot.com/search?q=upper+course
Upper Course
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Deep narrow valley (V shaped)
Interlocking spurs
Fast flowing river (erosion predominant)
Pot holes in the river bed
Rapids and Waterfalls
Deep narrow valleys with interlocking spurs
The main process at work is the downward or
vertical erosion of the stream bed. This cuts
into the landscape deepening the valley sides.
As the water twists around obstacles such as rocks and boulders the erosion forces undercut
outward bends and a snaking pattern is produced. From lower down the interlocking of the spurs
of land between the bends blocks the view up the valley.
V-shaped valley with interlocking spurs
Potholes:
Potholes are formed by corrasion. Pebbles carried by the river are
swirled around on the riverbed. This action erodes the rock on the
riverbed forming potholes. Over time, they may widen and join with
other potholes to form larger potholes, and the whole riverbed is
deepened.
Rapids:
Rapids are stretches of
fast-flowing water
tumbling over a rockyshallow riverbed. Different
resistance among rocks
cause rapids. They are
formed when the water
goes from one hard rock
that resists the water's
erosion to a softer rock that is easier eroded.
The Formation of a Waterfall
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Water passes over hard rock and erodes the softer rock below
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A plunge pool is formed and the river erodes backward as the water and rock
swirl around
Eventually the hard cap rock overhangs and collapses under gravity
This process continues over time and the waterfall moves backwards or
recedes to form a gorge
Variations may be caused by the rock structure.
(1) Rock layer is horizontal
(2) Rock layer dips upstream
The Middle Course
http://geobytesgcse.blogspot.com/2006/11/middle-course-of-river-meanders-ox-bow.html
Try this hyperlink to show you the middle section and its features
The Lower Course
http://geobytesgcse.blogspot.com/2006/11/lower-course-of-river-floodplains-and.html