Floodplains form along river banks when flooding deposits sediment. Levees are natural embankments of coarser sediment deposited along river banks during floods. Braided rivers divide into small streams separated by islands of deposited gravel and sand within the channel. Deltas are flat lands formed of sediments deposited at river mouths, with distributaries transporting sediment into the sea.

1. Depositional Landforms
•Floodplains
•Levees
• Braiding
•Delta
•Alluvial fan

2. Floodplains
• What ?
– A wide and flat valley
– Alluvium deposits on
riverbanks build it up
during repeated
flooding
– Provides fertile
alluvium for farming

4. How?
• Form when river overflows its banks during
flooding and spread large amount of sediment
over the banks
• When flood subsides or over, there is a decrease
in volume so that river deposits its load.
• Repeated flooding result in materials deposited
on the riverbanks forming a floodplain

6. Levees
What?
It is a natural
embankment on
the riverbanks
Where?
Form when coarser
alluvium is deposit
along the
riverbanks due to
flooding

7. How?
• Form during flood
• The coarser allluvium
is deposited near the
banks and finer
alluvium deposited
further from the banks
• The accumulation of
the coarser alluvium
along the river banks
formed a natural
raised banks called
levees

9. Braiding
• A river subdivides into
many smaller streams
within the channel
• Small islands / eyots
separate each stream
• Eyots are made up of
deposited loads such as
gravels and coarse sands

12. How?
• Depends on load-discharge relationship
• Short period of the year, some rivers carry a
heavy load which the rivers have difficulty in
removing
• When the river level falls rapidly, competence
and capacity reduced – channel deposit
materials within the channel
• Channel become broad and shallow with a low
hydraulic radius

13. (Braided river in southern Alaska.)

14. EYOTS

15. (Braided river at junction of Gakona and Copper River, Alaska)

16. Main Characteristics
1. Small islands or eyots of deposited material within the
channel.
2. A network of small intertwining channels converge and
diverge around the eyots.
3. At times of high discharge, braided streams carry a large
load of coarse material.
4. Braiding is a characteristic of streams with a variable
discharge
5. Very common in Semi-arid region where torrential rainfall
will lead to temporary stream with high discharge.

17. Delta
What?
• A piece of flat land
that
is made up of sediments
deposited at the river
mouth
• Streams found on the
delta known as
distributaries

18. • Flocculation occurs as fresh water mixes with
salt water - e.g where a river flows into the
sea -(then called brackish water), and is the
process by which tiny particles in suspension
like clay and silt (which under normal fresh
water conditions would likely never fall out of
suspension) coagulate with the salt in the
water by chemical reaction and become heavy
enough to ‘sink’ and be deposited
Flocculation

19. Typical Conditions:
• Calm and shallow seawater with gentle slope
• River deposits its load at the river mouth
• Wave in the sea is weak and sheltered coast
• More deposition due to active erosion in the
upper course

20. How does it form?
• Form when a river
approaches the calm
seawater
• Its velocity decreases
• Starts to deposits its load at
the river mouth
• Sediment continued to
accumulate into the sea-
forming delta, which is a flat
land

21. Material deposited: 3 layers
1. Bottomset beds – the lower part of the delta that
consists of fines material that can be transported
furtherest out to sea
2. Foreset beds – the middle layer where material
deposited is slightly coarser
3. Topset beds – the uppermost layer where
coarsest particles settle first

22. • Delta’s can be categorised into three main
shapes
– Arcuate
– Birds Foot
– Cuspate
Types of Delta

23. •The most common
shape of delta
•Characteristics:
curving shoreline
(smoothed by long
shore drift), distinct
pattern of drainage
(branching of
distributaries), and
typically more
‘gravely’ deposits .
•Example: the Nile
Delta
Arcuate
Delta’s

25. •‘Fingers’ of
deposition build
out into the sea
along the
distributaries
channels giving
an appearance
like a birds claw.
Typically with a
finer sediment
•Example: the
Mississippi delta
Birds Foot
Delta

28. • A cuspate
delta is shaped
like a tooth by
gentle but
regular
opposing
currents in the
water body the
river flows into,
or longshore
drift
• Example: The
river Ebro delta
in Spain
Cuspate
Delta

30. Alluvial Fans
• Are fan shaped similar to
delta but deposited on land
• Comes from a stream of a
steep mountain course and
enters a flatter plain with a
low gradient
• Sudden change of gradient
river lose energy  river
starts to deposit its load.
• The heavier (coarser) the
material will b deposited first
then the finer materials