How geology and physical processes form coastal landscapes of erosion and deposition; how human activity modifies them; the increasing risk of coastal flooding; and the costs, benefits and conflicts of hard, soft and sustainable coastal management.

What this dot point is asking

This is Edexcel GCSE Geography B (1GB0) Paper 2, Section A (Topic 4, The UK's evolving physical landscape), the coastal change and conflict depth study. Edexcel expects you to explain how geological structure (concordant/discordant, joints, faults) and rock type influence erosional landforms; how UK climate, marine (destructive waves) and sub-aerial processes (mass movement, weathering) shape coasts of erosion and the rate of coastal retreat; how transportation and deposition form depositional landforms; how human activity modifies coasts; the rising risk of coastal flooding; and the costs, benefits and conflicts of hard, soft and sustainable management.

Geology and coastal processes

The shape of a coast depends first on its geological structure and rock type.

The coast is shaped by marine and sub-aerial processes. The four types of marine erosion are hydraulic action (waves compress air into cracks, blasting rock apart), abrasion (waves throw sand and pebbles at the cliff), attrition (rocks knock together and become smaller and rounder) and solution (weak acids dissolve chalk and limestone). Sub-aerial processes are weathering (freeze-thaw, salt and biological action) and mass movement (slumping in saturated clay, rockfalls). UK climate matters too: a long fetch, frequent winter storms and the prevailing wind drive powerful destructive waves that increase erosion.

Erosional and depositional landforms

Erosion of a headland follows a clear sequence: a crack is widened to a cave, the cave is eroded through the headland to form an arch, the unsupported roof collapses to leave a stack, and further erosion reduces it to a stump (Old Harry Rocks, Dorset). A wave-cut platform forms as a cliff retreats: waves cut a wave-cut notch, the overhang collapses, the cliff retreats, and a gently sloping rocky platform is left.

Where waves lose energy, transportation by longshore drift (the zig-zag movement of sediment along the coast driven by the prevailing wind) and deposition by constructive waves build depositional landforms: beaches (sand or shingle), spits (ridges of sediment growing out where the coast changes direction, with a recurved end and salt marsh behind, such as Spurn Head on the Holderness coast) and bars (a spit grown across a bay, trapping a lagoon).

Human activity, flood risk and management

Human activities (coastal development, agriculture, industry and coastal management itself) directly and indirectly change coastal landscapes, for example by building on cliffs or interrupting sediment movement.

Coastal flood risk is rising because of climate change: more frequent and intense storms and rising sea level increase marine erosion and the threat to low-lying people and property. Managing the coast involves choosing between approaches with different costs, benefits and conflicts.

These choices cause conflict: residents want their homes protected, but defences are costly and protecting one place can speed erosion elsewhere, so decisions about whose land to defend (a simple cost-benefit analysis) are contested.

Try this

Q1. Explain how a spit is formed. [4 marks]

• Cue. Longshore drift carries sediment along the coast; where the coast changes direction the sediment is deposited in a ridge growing out into the sea, and a change in wind curls the end into a recurved hook, with salt marsh forming in the sheltered water behind.

Q2. Explain one reason coastal flood risk is increasing in the UK. [3 marks]

• Cue. Climate change is raising sea level and increasing the frequency and intensity of storms, so marine erosion and the threat of flooding to low-lying coastal land and property are rising.