Coastal Processes – Landforms and Management
GeographyEarth's Structure & LandformsAges 15–16
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Sign in to playA map of a 3 km stretch of coast with a cross-section wherever you choose. Set the wave type (constructive or destructive), fetch, prevailing wind direction, hard-rock resistance and the rock pattern (bands at right angles to the coast or parallel to it), then run hundreds of years: wave refraction focuses energy on headlands to form caves, arches, stacks, stumps and wave-cut platforms, bays are cut into soft rock, and longshore drift moves sand to build beaches and a spit across a river mouth. Choose a sea wall, rock armour, groynes, beach nourishment, dune regeneration or managed retreat and compare with doing nothing: homes lost, homes at flood risk, cost and the effect on the coast downdrift.
Lesson: Coastal processes, landforms and coastal management
What it shows
Waves erode, transport and deposit material along coasts. Bigger waves come from stronger winds blowing over a longer fetch. Destructive waves are high and steep with a strong backwash that removes sand; constructive waves are low with a strong swash that builds beaches. Where hard and soft rocks meet the sea, soft rock is worn back into bays and hard rock is left as headlands, where refraction focuses the waves. Waves arriving at an angle move sand along the shore by longshore drift, building a spit where the coast changes direction. Defending one stretch of coast often moves the problem further along it.
How to use
Choose Wave type, Coast type, Fetch, Wind direction and Hard rock and press Run. Use +100 years or a faster Speed to watch headlands, bays and the spit grow. Click the map to move the cross-section and see the cliff, platform, beach, swash and backwash. Then pick an option under Management at the town: the red dashed line shows the coast with no management, and the table compares homes lost, flood risk, cost and the coast downdrift. Straight coast starts again from year 0.
Parameters you can change
- Wave type Constructive (low, long, strong swash), Destructive (high, steep, strong backwash)
- Fetch (distance of open sea the wind blows over) 10–2000 km
- Angle of wind and waves from the shore-normal (positive: from the west) -60–60 °
- Coast type Discordant: rock bands at right angles to the coast, Concordant: a hard rock band parallel to the coast
- Resistance of hard rock compared with soft rock 3–30 times
- Management of the coast at the town Do nothing, Sea wall, Rock armour, Groynes, Beach nourishment, Dune regeneration, Managed retreat
Questions to explore
- Why are headlands attacked harder than bays, and why do bays have beaches?
- How does the prevailing wind direction decide which way sand drifts and where a spit grows?
- Groynes and sea walls protect the town; what harm do they do to the coast downdrift?
