River features Upstream portion River Channel small narrow

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