Fluvial Landforms

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Fluvial Landforms Middle course of river

• River Channel
• wider and deeper
• Volume of water greater than that in upper
  course.
• Gradient is less than upstream portion of the
  river course.

2
Fluvial Landforms Middle course of river

• River Valley
• More open V shape and wider valley floor.
• Lateral erosion of river more dominant.
• Weathering and mass wasting of valley sides.

3
Fluvial Landforms Middle course of river

• Work of river
• Vertical erosion is reduced.
• Increased volume of load and water in the river
  is used mainly for lateral erosion.
• Some energy is also used for transportation.
• Some deposition also occurs.

4
Fluvial Landforms Middle course of river
Meanders, river cliffs and slip-off slopes How
meanders begin to form is uncertain. They appear
to have their origins in times of flood and in
relatively straight sections where pools and
riffles develop.
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Fluvial Landforms Middle course of river
6
Fluvial Landforms Middle course of river
Pools areas of deeper water. Riffles areas of
shallow water. Spacing between pools and rivers
usually very regular 5x 6x of river width
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Fluvial Landforms Middle course of river
There is less friction in pools. Thus, river
flows faster and has more erosive
power. Increased friction in the riffles slows
water down and more deposition takes
place. Continuous erosion in the pools and
deposition in the river accentuates the slight
bends of a river.
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Fluvial Landforms Middle course of river
9
Fluvial Landforms Middle course of river
There exists a series secondary flow of water in
a river, other than the main flow. One of these
is called the helicoidal flow cockscrew
movement of water.
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Fluvial Landforms Middle course of river
Difference in velocity across the channel causes
unequal pressure distribution. Current from the
concave bank descends downwards, undercutting and
eroding the river side. Eroded material carried
along the bed and up the convex bank where it is
deposited.
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Fluvial Landforms Middle course of river
This current represents a cockscrew movement of
water because it continues downstream and repeats
the series of rotations.
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Fluvial Landforms Middle course of river
As erosion continues to undercut the concave
bank, eroded materials slump down into the river,
forming a steep river cliff.
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Fluvial Landforms Middle course of river
Continuous deposition on the convex bank makes it
shallow and deposition takes place. These
deposits on the convex bank build up into a
gently sloping slip-off slope.
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Fluvial Landforms Middle course of river
15
Fluvial Landforms Middle course of river
The channel has an asymmetrical
cross-section. Continued erosion on the concave
banks and deposition on the convex banks cause
the meanders to migrate laterally.
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Fluvial Landforms Middle course of river
17
Fluvial Landforms Middle course of river

• References
• Chong, M. (2001) Aspects of Physical Geography,
  Singapore Pekoe Books.
• Waugh, D. (2000) Geography An Integrated
  Approach, UK Nelson