The Middle And Lower Course Of A River By Fizah's Group

TRANSPORTATION MEANDERS OX

BOW LAKES FLOODPLAINS LEVEES DELTA BRAIDED CHANNEL

TRACTION This is where boulders and pebbles are rolled along the river bed at times of high discharge.

SALTATION Sand sized particles are bounced along the river bed by the flow of water

SUSPENSION Fine clay and sand particles are carried along within the water, even at low discharges SOLUTION Some minerals dissolve in water such as calcium carbonate. This requires very little energy.

Formation of slip-off slope & cliff

Riffle & pools

Formation of Ox bow Lakes

Strongest Current

Sediments deposited on inside of bend

Rapid Erosion on outer side of banks

The Gap between the two arms of the river has narrowed by erosion

River still Flows around meander

River Breaks through gap when in flood

Old Path of now dry river

Current along straighter path becomes dominant

Abandonded Meander or Oxbow lake

It is flat area of land either side of river forming valley floor. They are composed of alluvium deposited by river and form fertile soil.

Levees are high banks of silt close to the river channel which are formed by repeated river flooding. It is common in lower course of a river where there is floodplain.

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Floodplains and levees are formed by deposition in times of river flood. The river’s load is composed of different sized particles. When a river floods it deposits the heaviest of these particles first. The larger particles, often pebble-sized, form the levees. The sands, silts and clays are similarly sorted with the sands being deposited next, then the silts and finally the lightest clays. Every time the river floods deposition builds up the floodplain.

B lu f f L I n e

B l u f f L In e

Width of Floodplain

Coarser Material Deposited first Channel Layers of silt deposited by earlier floods

River

Bedload causes bed of river to rise

Levee

Finer Material Carried further

Deltas are areas of land at the mouth of a river jutting out into sea. Delta Deltas are often popular areas for farming due to the presence of fertile alluvial soils. Deltas are associated with the old stage of a river.

B)Arcuate/ fan-shaped Delta An arcuate delta forms when a river meets the sea in a place where the waves, currents, and tides are strong. It is often bow shaped and has a number of distributaries flowing across it. An example is the Nile delta of Egypt.

C) Estaurine Delta When the mouth of a river enters the sea and is inundated by the sea in a mix with freshwater and very little delta, it is called an estuary. An example of a estuarine delta is the Seine river delta in France or the Mackenzie river delta in Canada.