1. Combined Effects of
Erosion & Deposition
• Pools and Riffles
• Meanders and Ox-bow lakes
• River Terraces

2. Pools and Riffles
Pools: are areas of deep
water and greater
erosion.
(Energy build up due to
less friction)
Riffles : are areas of shallow
water caused by
deposition of coarse
sediment

4. Sinuosity
Is the curving nature of a river’s course.

5. Thalweg
The position of
the rivers
fastest flowing
current.
(Least friction,
greater energy,
greatest
erosion)

6.  Thalweg – the line of fastest flow in a river

8. Pool
Riffle

9. Meander

10. Meander – Bends in course of a river channel

11. How occur?
1. Begin when a river
approaches its middle
course & gradient channel
is less steep.
2. It results from helicoidal
flow with faster current
spirals downstream in
corkscrew fashion.
3. Movement result in
erosion on outside bend of
meander to form river cliff
and deposit on inside bend
called slip off slope.

12. Slip-off slope River cliff
Point bar
Thalweg

13. Material is deposited on the inside of a meander bend as a
point bar.
At point
bars
particles
are usually
graded in
size
(sorted)
with the
largest
particles
found on
the
upstream
side.

14. As erosion occurs on the outside of the meander bend, the
whole meander migrates downstream.
Material
forming
the point
bar
becomes a
contribut
ory factor
in
floodplain
formation.

15. As sinuosity Temporary
straightening of
increases,
the channel
during flood
means the main
events the flow is in mid
flow may channel, meaning
cut of the deposition now
meander occurs at the
bend at the river banks and
neck, thus the old curve is
shortening therefore
its course. abandoned to
leave an ox-bow
lake.

18. River / Fluvial Terraces
• Benches on the valley
side
• Formed when a river cuts
into a former floodplain
Following vertical erosion
caused by rejuvenation
• Can be formed in bedrock
• Result from AGGRADATION
f0llowed by INCISION of a
river valley

19. • T = terraces
• C = confluence