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River features – Upstream portion. River Channel: small, narrow, rough and usually shallow. When rivers have to flow round obstacles of hard rocks in its path (spurs), it develops a winding course. River features – Upstream portion. River features – Upstream portion.

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River features – Upstream portion

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River features – Upstream portion

River Channel: small, narrow, rough and usually shallow.

When rivers have to flow round obstacles of hard rocks in its path (spurs), it develops a winding course.


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River features – Upstream portion


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River features – Upstream portion

  • Rapids: a series of short and fast-flowing turbulent falls of water along a part of the river.

  • Water is relatively shallow.


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River features – Upstream portion

  • Formation of rapids:

  • River flows over an area of alternating bands of gently inclined resistant and less resistant rocks.

  • Less resistant rocks are eroded faster.

  • river flows swiftly when it flows over outcrops of resistant rocks.


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River features – Upstream portion

2) Waterfalls

Sudden fall of water along a course of a river.

Water plunges down almost vertically and rapidly into a deep valley


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River features – Upstream portion

  • Formation of waterfall:

  • forms when a river flows from a band of resistant rock to less resistant rock.

  • band of resistant rock can lie horizontally, vertically or dip upstream

  • less resistant rock that lies downstream will be eroded faster than the resistant one


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River features – Upstream portion

  • Formation of waterfall:

  • differential erosion causes a change in gradient of river.

  • over time, the river bed will be steepened.

  • water plunges down almost vertically and rapidly as a waterfall.


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  • Formation of waterfall (cont’d)

  • when faulting causes land to be displaced, waterfalls can also form.

  • One block of land will be uplifted relative to the adjacent block.

  • This displacement causes a difference in height.

  • Water cascades down the fault scarp.


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River features – Upstream portion

3) Plunge Pools

A depression at the foot of a waterfall.

This depression is excavated, enlarged and deepened by hydraulic action of the plunging water.

Rock debris erodes the depression by abrasion to furthur enlarge and deepen it.


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River features – Upstream portion

4) Gorges

Deep narrow valleys with almost vertical sides.


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5) Potholes

Depressions of different sizes in the river bed.

Formed by river abrasion.

Abrasive action especially effective in flood conditions


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River features – Upstream portion

http://library.thinkquest.org/28022/


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