(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

Answer Details

(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.