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
1) Rapids: a series of short and fast-flowing
turbulent falls of water along a part of the
river.
Water is relatively shallow.
River features – Upstream portion
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.
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
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
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.
River features – Upstream portion
River features – Upstream portion
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.
River features – Upstream portion
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.
River features – Upstream portion
4) Gorges
Deep narrow valleys with almost vertical
sides.
River features – Upstream portion
River features – Upstream portion
River features – Upstream portion
5) Potholes
Depressions of different sizes in the river bed.
Formed by river abrasion.
Abrasive action especially effective in flood
conditions
River features – Upstream portion
River features – Upstream portion
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