2.3 Coasts: Describe coastal processes, landforms and management strategies.

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Coastal Processes, Landforms, Opportunities, Hazards & Management (IGCSE 0460 – Topic 2.3)

1. Syllabus Checklist – Quick Review

Syllabus requirement Coverage in the notes Suggested improvement
2.1 Physical processes that shape the coast (hydraulic action, corrosion, corrasion, attrition, long‑shore drift, deposition, wave refraction) All seven processes listed with description and typical landform. Add short example for each process (e.g., “hydraulic action – sea‑cave formation at Durdle Door”).
2.2 Coastal landforms (erosional, depositional, discordant & concordant coasts) Erosional and depositional landforms listed; discordant & concordant coasts described. Include a concise table linking each landform to its dominant process and a real‑world example.
2.3 Opportunities and hazards of living near the coast Opportunities and hazards presented in bullet lists. Group hazards under the relevant process (e.g., erosion‑related, flooding‑related) for clearer cause‑effect links.
2.4 Coastal management – hard, soft and managed retreat Hard, soft and integrated approaches described; comparison table provided. Add a short “when to use which method” decision flow‑chart description.

2. Physical Processes that Shape Coasts

Process How it works (key idea) Typical landform / example
Hydraulic action Wave pressure forces air into cracks; the compressed air expands explosively, widening the crack. Sea caves (e.g., Durdle Door, UK)
Corrosion (solution) Seawater, slightly acidic because of dissolved CO₂, dissolves soluble rocks such as limestone. Enlarged fissures, sea caves in limestone coasts
Corrasion (abrasion) Sand, pebbles and rock fragments are hurled against the cliff base by the swash, grinding it away. Wave‑cut platforms, cliff retreat
Attrition Rocks and pebbles collide while being moved by waves, becoming smaller and smoother. Rounded beach pebbles; supply of fine sediment
Long‑shore drift Waves approach the shore at an angle; swash moves sediment up‑coast, backwash moves it down‑coast, producing a net movement along the shore. Spits, bars, beach accretion on the up‑drift side of groynes
Deposition When wave energy falls (e.g., in sheltered water), the carried sediment settles out. Beaches, spits, offshore bars, tombolos, dunes
Wave refraction Wave fronts bend as they enter shallow water; the part in shallower water slows, aligning the wave more parallel to the coast. Energy concentrated on headlands, reduced on bays

Wave energy formula (useful for exam calculations):

$$E = \frac{1}{8}\,\rho\,g\,H^{2}$$

  • ρ = density of seawater (≈ 1025 kg m⁻³)
  • g = 9.81 m s⁻²
  • H = wave height (m)

Constructive vs. Destructive Waves

Type Key characteristics Typical coastal effect
Constructive Low height, long wavelength, gentle swell; strong swash, weak backwash. Net deposition → wide, gently sloping beaches; formation of offshore bars.
Destructive High height, short wavelength, steep breaking; strong backwash. Net erosion → steep beaches, cliffs, wave‑cut platforms; removal of beach material.

3. Coastal Landforms

3.1 Erosional Landforms (dominant erosion)

  • Headland – protruding point of resistant rock (e.g., Old Harry, Cornwall).
  • Bay – recessed area of less resistant rock between headlands (e.g., St Ives Bay).
  • Cliff – steep rock face formed by wave erosion.
  • Wave‑cut platform – flat, often rocky area at the base of a retreating cliff.
  • Sea cave – hollowed out by hydraulic action and solution.
  • Sea arch – formed when a cave breaks through a headland.
  • Sea stack – isolated column left after an arch collapses.
  • Sea stump – low, flat remnant of a heavily eroded stack.

3.2 Depositional Landforms (dominant deposition)

  • Beach – accumulation of sand or shingle where the swash deposits material.
  • Spit – narrow finger of sediment extending from a coast at a change in direction (e.g., Spurn Head, England).
  • Offshore bar – ridge of sand/shingle parallel to the shore, often attached to a spit.
  • Lagoon – shallow water body protected from the sea by a bar or spit.
  • Tombolo – sand/shingle bar that joins an island to the mainland (e.g., Chesil Beach, Dorset).
  • Barrier beach/shoreline – long, parallel strip of sand protecting a lagoon or estuary.
  • Dune – wind‑blown accumulation of sand on a beach, usually stabilised by vegetation.

3.3 Coast Types – Influence of Rock Arrangement

Coast type Rock arrangement Typical landforms
Discordant coast Hard and soft rock bands run perpendicular to the shoreline. Prominent headlands and deep bays; often a series of sea arches and stacks.
Concordant coast Rock layers run parallel to the shoreline. Long, uniform beaches; occasional breaches where a softer band is exposed, forming a lagoon.

3.4 Summary Table – Landform, Dominant Process & Example

Landform Dominant process Typical location / example
Headland Erosion of resistant rock Discordant coast – Lulworth Cove, Dorset
Bay Erosion of weaker rock Between headlands – St Ives Bay, Cornwall
Sea stack Continued erosion of an arch Old Man of Storr, Scotland
Spit Long‑shore drift & deposition Spurn Head, East Yorkshire
Offshore bar Deposition in shallow water Bar at the mouth of the River Exeter
Dune Wind transport & deposition of sand Sand dunes of the Norfolk Coast

4. Opportunities & Hazards of Living Near the Coast

4.1 Opportunities (benefits)

  • Tourism & recreation – beaches, cliffs, water sports.
  • Fishing & aquaculture – rich marine resources.
  • Maritime transport – ports, harbours, shipping lanes.
  • Renewable energy – offshore wind farms, tidal turbines.
  • Natural habitats – dunes, salt‑marshes, estuaries support biodiversity and provide ecosystem services.

4.2 Hazards (grouped by cause)

  • Erosion‑related
    • Coastal erosion – loss of land, damage to buildings and infrastructure.
    • Landslides & cliff collapse – undercutting or heavy rain destabilises cliffs.
  • Flood‑related
    • Storm surge & coastal flooding – temporary sea‑level rise during severe storms.
    • High tides & king tides – regular but extreme inundation events.
  • Material‑related
    • Salt spray & corrosion – accelerates deterioration of metal, concrete and timber.

5. Coastal Management Strategies

Management seeks a sustainable balance between protecting people/property and allowing natural coastal processes. Strategies fall into three categories.

5.1 Hard Engineering (structural solutions)

  • Sea wall – vertical or sloping concrete/stone barrier that reflects wave energy.
  • Groynes – perpendicular structures that trap long‑shore drift sediment, building up the beach in front of them.
  • Revetments – sloping armour of rock, concrete or timber placed on the foreshore to absorb wave energy.
  • Rock armour (rip‑rap) – large stones laid on a slope or at the base of a cliff to dissipate energy.

5.2 Soft Engineering (working with natural processes)

  • Beach nourishment – adding sand or shingle to widen a beach and provide a buffer.
  • Dune regeneration – planting marram grass or other stabilising vegetation and installing sand fences.
  • Managed realignment (retreat) – deliberately allowing a low‑lying area to flood, creating salt‑marsh or mud‑flat habitats.

5.3 Integrated / Sustainable Approaches

  • Combining hard and soft measures (e.g., sea wall backed by a nourished beach).
  • Land‑use planning – restricting development within the coastal erosion hazard zone.
  • Early‑warning systems for storm surge and high tides.
  • Community involvement, regular monitoring and adaptive management.

5.4 Decision‑making Flow (when to use which method)

  1. Is the main problem erosion of a cliff?
    • Yes → consider sea wall or rock armour.
    • No → go to 2.
  2. Is the problem loss of beach width that also affects tourism?
    • Yes → beach nourishment ± groynes; dune regeneration if wind‑drift is significant.
    • No → go to 3.
  3. Is the area low‑lying and the cost of protection > long‑term benefit?
    • Yes → consider managed realignment.
    • No → evaluate a hybrid hard‑soft solution.

5.5 Comparison of Management Options

Strategy Advantages Disadvantages
Sea wall Immediate, long‑term protection; low maintenance after construction. High initial cost; can increase downdrift erosion; visual impact.
Groynes Builds up beach locally; relatively inexpensive. May cause erosion further down‑drift; requires regular inspection.
Revetments / rock armour Effective on steep cliffs; dissipates wave energy. Expensive to install; can be unsightly; may affect natural habitats.
Beach nourishment Preserves natural appearance; enhances recreation; can be combined with groynes. Recurring cost; sand can be lost quickly; may disturb marine life during placement.
Dune regeneration Low cost; improves biodiversity; natural defence against moderate storms. Less effective against extreme events; requires ongoing vegetation management.
Managed retreat Allows natural processes; creates valuable habitats; long‑term cost saving. Loss of land, property and infrastructure; often socially unpopular.

6. Suggested Diagrams for Revision or Exam Practice

  • Cross‑section of a headland showing cliff, wave‑cut platform, sea cave, arch, stack and stump.
  • Wave refraction diagram around a headland, indicating zones of high and low energy.
  • Long‑shore drift illustration with a spit, offshore bar, lagoon and direction of sediment transport.
  • Side‑by‑side comparison of a hard‑engineered coast (sea wall + groyne) and a soft‑engineered coast (beach nourishment + dune regeneration) on a coastal profile.
  • Sketch of discordant vs. concordant coastlines, labeling typical landforms for each.
  • Flow‑chart (as shown in 5.4) summarising the decision‑making process for selecting a management strategy.

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