(a)(i) River Capture: This is also called river piracy or river beheading. It results when a river through head water of erosion into a water divide cuts up the headwater of another but a weaker river. The river pirated is called misfit and the point of capture is called elbow of capture The valley below the elbow is called wind gap.
(i) Waterfall: This is formed as a result of unequal resistance of hard and soft rocks transverse by a river. The out crop of a band of hard rock may cause a river to fall downstream in greater dimension from some heights called waterfall

(b) One way in which river capture is useful to man is channelization of water away from settlements while waterfall is useful for the generation of hydro-electric power