Coastal Landscapes and Change
Coastal Landscapes and Change
This domain examines coastal processes, landform development, sediment budgets, sea-level change and management. Exam answers should link wave energy and sediment movement to specific landforms and evaluate management using costs, benefits and sediment-cell effects.
Core rules
- Wave energy depends on fetch, wind speed and duration. Constructive waves have low height, long wavelength and strong swash; destructive waves are high, short and have strong backwash.
- Erosion processes include hydraulic action, abrasion, attrition and solution. Longshore drift transports sediment along the coast in the direction of dominant swash.
- Cliff retreat produces wave-cut notches and platforms; headland erosion can form caves, arches, stacks and stumps. Deposition builds beaches, spits, bars, tombolos, salt marshes and dunes.
- Sediment cells are littoral compartments; interruption of sediment supply can cause erosion downdrift.
- Sea-level change is eustatic (water volume or global change) or isostatic (land movement). Management is hard engineering, soft engineering or managed retreat, and should be evaluated at the sediment-cell scale.
Worked example
A spit forms where longshore drift carries sand past a river mouth, and the current slows in shelter. Reasoning: sediment supply must exceed removal; the river mouth reduces wave energy; the spit grows in the drift direction and may recurve where wave direction changes; salt marsh develops in the sheltered low-energy area behind it. If the river is dredged or sediment supply is cut off, the spit may erode.
Traps
Do not say longshore drift moves sediment inland; it moves it along the shore. Do not reverse the cave-arch-stack sequence. Do not treat hard engineering as eliminating erosion everywhere, since it often transfers erosion downdrift. Do not ignore sediment budget when explaining change.