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Slide 1

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Raised banks of alluvium along the edges of an river. When a
river floods its banks, the water spreads out and rapidly loses
its competence. Deposition occurs close to the banks, and
increases their height. When the river is not flooding,
sediment is deposited on the river bed. After a period of time
the river and its levees are raised above the level of the
surrounding flood plain.…read more

Slide 2

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Formation of levees
Levees are formed in the lower course of rivers. When a river floods over
its banks, the water spreads out, there is a decrease in velocity, and it
deposits sediment. Over time, the river's banks are built up above the
level of the rest of the floodplain. The resulting ridges are called natural
In the lower course of the long profile
there is a gentle gradient and when the
river floods it has high discharge. If it
does flood the velocity of the water falls
as it overflows the banks and the river
deposits it's load because the
competence of the river is reduced.
These are formed as the heavier
sediment carried by floodwater settle
first, close to the channel, while finer
material travels further over the
floodplain.…read more

Slide 3

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A floodplain is an area of land at either side of the river banks. When
rivers are at bankfull stage they may spill over the edges of the channel to
land known as floodplains. Floodplains are areas of flat land either side of
the river channel. The river channels are shallow with vast wetted
perimeters which result in more frictional contact and lower velocities than
water in the main channel. These factors combine to deposit fine sediment
over the floodplain, increasing fertility and height to the land as further
floods may add to the alluvium.…read more

Slide 4

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Formation of Floodplains
They are created as a result of both erosion and deposition, although
accumulation of sediment indicates they are primarily depositional
features. Floodplains consist of deposited silts and clays. Over time the
floodplain becomes wider and the depth of sediment increases. The
width is determined by the amount of meander migration and lateral
erosion that has occurred. They are common in the lower course as
this is the widest and deepest area, and similar in appearance to the
floor of an old lake. The floodplain is generally flat by the river banks . It
has a gentle slope down-stream.
Point bar deposits and meander scars are incorporated into the
floodplain. They are stabilized by vegetation as the meanders migrate
and abandon their former courses. The velocity of the river decreases
as the water overflows and deposition takes place. Because the lower
course has a gentler gradient the floodplains tend to be flat and built up
over time after periodic floods.…read more

Slide 5

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Changes in Floodplain
Floodplain Deposits
Floodplain Features…read more


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