Theory question 307
Rivers and River LandformsWith appropriate diagrams, outline three conditions under which the following features can be formed: (a) river capture; (b) waterfall.
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(a) River capture: one river must have greater erosive power (steeper gradient, more water) than its neighbour; the stronger river erodes headward (back towards its source) through soft rock; the two rivers must be close together, separated by a low watershed; the capturing river must flow at a lower level; result: elbow of capture, misfit stream and wind gap. Diagram: before and after capture.
(b) Waterfall: a band of hard rock lying across the river over soft rock, which is eroded faster (differential erosion); a fault scarp across the river course; a plateau edge or escarpment; a hanging valley left by glaciation; rejuvenation (knick point); a lava flow damming the valley; examples: Kwa Falls, Victoria Falls, Owu Falls. Diagram: hard rock over soft rock with plunge pool.
Draw before and after diagrams for capture.