(a) With the aid of annotated diagrams, describe the characteristics of various stages of river course (b) List three ways by which rivers are beneficial

(a) Characteristics of the stages of a river course

A river is usually divided into three stages from source to mouth.

1. Youthful (upper) stage

• Steep gradient and swift flow; vertical (downward) erosion dominates.
• Deep, narrow V-shaped valleys, interlocking spurs, waterfalls, rapids and gorges.
• Small load of large, angular boulders.

2. Mature (middle) stage

• Gentler gradient; the river erodes both downward and sideways (lateral erosion begins).
• Wider valley, meanders begin to form, and river cliffs and slip-off slopes appear.
• Both erosion and deposition take place; the load is smaller and more rounded.

3. Old (lower) stage

• Very gentle gradient and slow flow; deposition dominates.
• Broad, flat floodplain with large meanders, ox-bow lakes, levees, deltas and estuaries at the mouth.
• Fine load of silt and mud deposited over the plain.

(b) Three ways rivers are beneficial

• Provide water for domestic use, irrigation and industry.
• Serve as routes for inland water transport, and support fishing.
• Used to generate hydro-electric power, and their floodplains provide fertile soil for farming.