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GCSE Geography 02 — Coastal Environments

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Topics include Waves and coastal processes: erosion, weathering, and mass movement, Sediment transport and longshore drift, Erosional landforms: cliffs, wave-cut platforms, caves–arches–stacks, Depositional landforms: beaches, spits, bars, dunes, salt marsh, Coastal systems and sediment budgets, Coastal flooding: storms, storm surges, and sea-level rise, Coastal management: hard engineering, soft engineering, and managed retreat, and Case studies: applying processes and management to real coasts.

Geography EN
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Sediment transport and longshore drift

Sediment is moved along coasts mainly by longshore drift. Understanding the process helps explain why spits form and why groynes can cause erosion downdrift.

Key points

  • Longshore drift happens when waves approach the shore at an angle.
  • Swash carries sediment up the beach at the wave angle; backwash returns it straight down under gravity.
  • Repeated swash/backwash moves sediment in a zig-zag pattern along the coast.
  • Sediment supply can come from cliff erosion, rivers, and offshore sources.
  • Interrupting longshore drift (e.g., groynes) builds beaches updrift but can starve downdrift coasts.

Worked example

Question

A new groyne is built on a beach with longshore drift. Explain one positive and one negative impact.

Solution

Positive: the groyne traps sediment moving along the coast, building up a wider beach. A wider beach absorbs wave energy and can reduce erosion and flood risk locally. Negative: less sediment reaches downdrift areas, so beaches there may narrow, exposing cliffs to wave energy and increasing erosion and flood risk further along the coast.

Common pitfalls

  • Saying backwash moves at the same angle as swash (backwash is usually perpendicular).
  • Forgetting to mention that waves approach at an angle in the first place.
  • Ignoring knock-on effects downdrift when discussing groynes.

Prerequisites

  • co_processes_waves
  • Prerequisite knowledge (auto-added).
Further resources