Overview
This lecture covers A-level coastal geography, focusing on coastal features, processes shaping coastlines, sea level change, coastal risks, and management strategies.
Coastal Features and Zones
- The littoral zone is the coastal area including land, intertidal, and nearshore sea.
- Four main zones: backshore (above high tide, only affected during storms), foreshore (between high and low tide, main wave action), nearshore (low tide mark to breaker zone), and offshore (beyond breaker, minimal sediment movement).
- Tides and wave energy shape these features and their dynamic changes.
Types of Coastlines and Geological Influences
- Rocky coastlines have high relief and resistant geology, found in high-energy environments.
- Coastal plains are low energy, low relief, and less resistant (e.g., sandy/estuarine).
- Concordant coastlines have rock layers parallel to the shore; discordant have layers perpendicular, forming headlands and bays from differential erosion.
- Geological structure (strata, bedding planes, joints, folds, faults, dip) influences erosion and creates micro-features like caves and notches.
- Cliff profiles (horizontal dip, seawards dip, landward dip) affect cliff stability.
Marine Processes: Erosion, Transport, Deposition
- Constructive waves build beaches (strong swash, weak backwash); destructive waves erode them (weak swash, strong backwash).
- Four erosion types: hydraulic action, abrasion, attrition, corrosion.
- Transportation by traction (rolling), saltation (bouncing), suspension (floating), solution (dissolved).
- Longshore drift moves material along coasts in a zigzag.
- Deposition forms spits, bars, tombolos; gravity settling and flocculation are key processes.
Vegetation and Coastal Succession
- Halophytes are salt-tolerant plants; xerophytes live in dry environments.
- Sand dune succession starts with pioneer plants and progresses to climax woodland.
- Salt marsh succession begins on mudflats with pioneer species, leading to increasingly complex vegetation as land builds.
Sea Level Change and Landforms
- Post-glacial adjustment (isostatic rebound) and eustatic (global water volume) changes drive sea level changes.
- Uplift creates raised beaches/fossil cliffs; submergence forms rias (drowned river valleys), fjords (drowned glacial valleys), and Dalmatian coasts.
- Modern sea level rise is caused by thermal expansion, glacier and ice sheet melt, and tectonic uplift.
Rapid Coastal Retreat and Flooding
- Factors: high-energy waves (long fetch), weak rock types, geological structures, mass movements, and human activities (e.g., damming).
- Flood-prone areas: coastal plains, estuaries, deltas.
- Bangladesh is highly vulnerable due to geography, high population, climate, river networks, and loss of natural barriers.
Impacts of Coastal Change
- Social impacts: displacement, loss of homes/livelihoods, health effects, loss of amenities.
- Economic impacts: loss of land, business/property damage, decreased property values, infrastructure loss.
- Developing (e.g., Philippines) and developed (e.g., Australia) countries face unique but significant risks.
- Climate change increases flood and storm risks; environmental refugees may result (e.g., Maldives).
Coastal Management Approaches
- Soft engineering: beach nourishment, cliff regrading/drainage, dune stabilization; eco-friendly but less permanent.
- Hard engineering: riprap, breakwaters, seawalls, revetments, groynes; effective but expensive and environmentally impactful.
- Sustainable methods include coral reef protection, replanting mangroves, beach nourishment, and integrated management.
- Shoreline Management Plans (SMPs) strategies: no intervention, managed realignment, hold the line, advance the line; plans balance cost, risk, and social/environmental needs.
Key Terms & Definitions
- Littoral zone — area between land and sea, includes shore and shallow sea.
- Concordant/discordant coastline — rock layers parallel/perpendicular to the shore.
- Eustatic change — global sea level change due to water volume.
- Isostatic change — local land level changes (uplift/subsidence).
- Longshore drift — movement of sediment along the coast due to angled waves.
- Soft/hard engineering — coastal management with/without unnatural structures.
Action Items / Next Steps
- Review case studies on Holderness Coast and North Sea storm surges.
- Practice sketching diagrams of landforms (spits, bars, dunes, rias, fjords).
- Learn key definitions and processes for potential exam questions on coastal management.