Braided Channels , Waterfalls and Rapids.

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Braided channels are a result of several channels divided

into sub-channels by temporary islands called 'eyots' or 'braid bars'. This feature of rivers

often contains larger loads of sand and gravel.

WHAT ARE BRAIDED CHANNELS?

Deposition occurs when the river has reached the threshold level of sediment load. This (reaching the threshold level) may occur due to rapid evaporation and infiltration after heavy rainfall, leading to the deposition of sediment.

Braided channels are most likely to occur when there is a variance in the discharge of a river, steep gradient and a lot of sedimentary material. Such environments include:

The banks form from the sand and gravel transported and so cause the banks to be unstable (as they are made of such fine and easily eroded sediment). When the banks do erode via lateral erosion, this causes the channel to become wider, in relation to its depth.

The rivers may become blocked and ‘chocked’ with sandbars and other channels that constantly change in direction.

HOW DO THEY FORM?

WHERE DO THEY OCCUR?

Semi-arid areas on low reliefed landthat tend to receiive the river from mountainous areas.

Glacial streams with variable annual discharge. In springs, meltwater adds to the discharge and competence, enabling the river to carry more sediment, therefore transporting more load. As the temperature drops and river level falls, discharge decreases, causing the river todeposit its loadas 'islands' in the channel.

Cross-section of a braided channel.

CASE STUDY EXAMPLES:

River Brahmaputra, runs through India, Bangladesh and China.

Tagliamento river, Italy.

http://geographyas.info/rivers/river-landforms/

WHAT ARE WATERFALLS AND RAPIDS?

Waterfalls and rapids occur when there is a sudden change in gradient in a river; can be described as a 'knickpoint'.

Although formed in similar ways, waterfalls are more dramatic features, as a result of:

A band of resistant (hard) rock laying along the course of the river.

The edge of a plateau

Braided Channels

Waterfalls and Rapids

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