River Morphology: Contrasting the Source and Mouth Shapes

A river’s form changes dramatically from source to mouth.

Source (Headwaters)

• Upland (mountains/hills)
• Narrow, steep channel
• High gradient, fast flow
• Cascades, waterfalls common

Mouth (Terminus)

Where the river meets a larger water body. Shape depends on sediment load and receiving basin:

• Delta: Fan-shaped sediment deposit (low gradient, calm receiving water).
• Estuary: Funnel-shaped mixing zone of fresh and salt water.
• River Mouth Bar: Elongate or crescentic shoal at entrance.

Longitudinal Evolution

Channel widens, gradient decreases, flow slows, sediment size fines downstream. The mouth reflects the river’s integrated sediment delivery and the receiving basin’s energy.