What causes a river to develop meanders?

Correct — C. Meanders form where a river crosses gentle, flat ground and its erosion works sideways rather than downwards.

On each bend the flow is fastest on the outside, so it erodes the outer (cut) bank and drops sediment on the inner bank as a point bar. The bends grow and migrate across the floodplain: lateral erosion in flat terrain.

Why the others are wrong

• (a)
  High-altitude origin — A high-altitude origin puts a river on steep slopes, where it cuts downwards into V-shaped valleys and gorges. Meanders belong to low, gentle ground, usually far from the source.
• (b)
  Sudden tectonic uplift — Tectonic uplift makes a river cut down. A meandering river on rising land sinks its existing bends into rock as incised meanders, so uplift deepens loops rather than creating them.
• (d)
  Ocean current influence — Ocean currents act at sea and along coasts. A river's bends form inland, from its own flow working on its banks.

A river's work changes along its course. Near the source, on steep gradients, it erodes mainly downwards, cutting V-shaped valleys.

On a flat floodplain it works sideways. The outer bank of each bend is worn back and the inner bank built up, so the loops widen and wander.

When the narrow neck between two loops is cut through, often in a flood, the abandoned loop becomes an ox-bow lake.

Key facts

• A meandering river erodes the outer (cut) bank of each bend and deposits on the inner bank.
• The deposit on the inner bank of a meander is called a point bar.
• An ox-bow lake forms when a meander loop is cut off, often during a flood.
• Incised or entrenched meanders form when a meandering river cuts down into bedrock after uplift or a fall in base level.

Common traps

• Choosing uplift because entrenched meanders are linked to it, though uplift deepens bends that already exist.
• Placing meanders near a river's source, where steep slopes favour downcutting.

No directly related past PYQ was found.