River landscapes: processes and landforms

OCR J383 Paper 1 tests river landscapes with both short-answer (2–4 marks) and extended writing (8 marks). You must be able to name and explain processes AND describe how specific landforms are created — using the correct geographical terminology.

River processes

Erosion (four types)

Process	Description
Hydraulic action	The force of water and the pressure of air trapped in cracks erodes the river bed and banks
Abrasion (corrasion)	Sediment carried by the river scrapes and wears away the bed and banks (like sandpaper)
Attrition	Sediment particles knock together and break into smaller, rounder pieces
Solution (corrosion)	Soluble rocks (e.g. limestone) dissolve in the river water

Transportation (four types)

Type	Process
Traction	Boulders rolled along the river bed
Saltation	Pebbles bounced along the bed in a hopping motion
Suspension	Fine silt and clay carried within the water
Solution	Dissolved minerals carried in the water

Heavier sediment is transported closer to the source; fine sediment is carried furthest.

Deposition

Occurs when the river loses energy (velocity decreases). This happens when:

• The river enters a lake or the sea.
• Gradient decreases.
• Volume decreases (drought).
• Obstruction occurs.

The Hjulstrom Curve shows the relationship between velocity, particle size and erosion/deposition.

Upper course landforms

V-shaped valleys and interlocking spurs

• Location: near the source; steep gradient; fast-flowing.
• Process: predominantly vertical erosion (downcutting) by hydraulic action and abrasion.
• Lateral erosion is minimal → V-shaped cross-section.
• Interlocking spurs: the river winds around resistant rock outcrops; viewed from above, spurs from opposite sides interlock like teeth on a zip.

Waterfalls and gorges

Formation:

1. River flows over a band of hard rock overlying softer rock.
2. Softer rock erodes faster (hydraulic action, abrasion) → undercutting of hard rock.
3. Hard rock overhangs → eventually collapses.
4. Collapsed material is swirled in the plunge pool, deepening it by abrasion.
5. Process repeats → waterfall retreats upstream → gorge forms behind it.

Middle course landforms

Meanders

• Location: middle course; gentler gradient; lateral erosion dominates.
• Outside bend (river cliff / cut-bank): fastest current → erosion by hydraulic action and abrasion → steep bank.
• Inside bend (slip-off slope): slowest current → deposition → gentle, sandy bank.
• Over time, meanders migrate downstream and become more pronounced.

Oxbow lakes

Formation:

1. Meander becomes very pronounced; the neck narrows.
2. During a flood the river cuts through the neck (erosion).
3. River takes the shorter, straight route.
4. Deposition seals off the old meander loop.
5. Oxbow lake formed — a crescent-shaped lake.

Lower course landforms

Floodplains

• Very flat land either side of the river.
• During floods, river overflows and deposits alluvium (fine silt).
• Alluvium is very fertile → excellent for agriculture.
• Levées: natural embankments built up by repeated flooding — coarser material deposited first (closest to channel), finer material further away.

Common OCR exam mistakes

1. Describing waterfall formation without mentioning the hard/soft rock distinction — the differential erosion is the key mechanism.
2. Confusing the outside and inside bend of a meander — remember: outside = erosion = river cliff; inside = deposition = slip-off slope.
3. Saying "the river erodes sideways" without specifying which process — always name hydraulic action or abrasion.
4. Forgetting to say the oxbow lake is sealed by deposition — many students explain the cutting of the neck but not the sealing.