Coasts

• Coastal zones


  Develop from interactions between the winds, waves and currents. These energy flows work with geological characteristics of the coast (i.e. sediments) to produce distinctive landscapes, including rocky, sandy and estuarine coastlines.
• Coastal zones are important as the majority of the world's population inhabit these regions. Coastal zones are rapidly changing due to the dynamic interaction between oceans and the land.
• Littoral zone


  The near shore area where sunlight penetrates sediments, allowing for aquatic life to flourish, but faces rapid continuous change.
• Zones of the littoral zone


  • Backshore
  • Nearshore
  • Offshore
• Criteria to identify coasts

  • Geology (rocky coast, muddy coast, sandy coast etc.)
  • Changes to sea level
  • Inputs from rivers, waves and tides (e.g. Barrier coasts, Arctic coasts)
• Rocky coasts


  • Characterised by their erosional features. The main erosional processes are: mechanical wave erosion, abrasion, weathering, bio-erosion and mass movements by rock falls, slides and flows.
• Coastal plain landscapes (sandy and estuarine)

  • Found in low relief areas. They result from the supply of sediment from offshore sources like rivers.
• Geological structures

  • Jointing
  • Dip
  • Faulting
  • Folding
• Concordant coastlines


  Where beds, layers and rocks are folded into ridges that run parallel to the coast. Usually, concordant coastlines have the same type of rock along its length. Dalmatian and Haff morphology occurs on these coastlines.
• Discordant coastlines


  Bands of rock and layers run perpendicular to the coastline. Usually the geology alternates between strata of hard rock and soft rocks. Headlands and Bays occur at these coastlines as erosion resistance is different between rocks, so they wear away at different speeds.
• Bedrock


  Made of indigenous, sedimentary and metamorphic rocks which determines erosion rates. The harder the rock and the more impermeable it is, lower the rate of erosion and coastal recession.
• Coastal recession


  Erosion occurs at the foot of a cliff, creating a notch. Material above the notch collapses and is washed away. Repeated collapsing causes the cliff to retreat further away.
• Vegetation stabilises sandy coastlines, provides habitats and flood defences.
• Constructive waves


  Low waves that influence beach morphology and sediment profiles in the short and long term.
• Destructive waves


  Created in storm conditions when wind is powerful and waves are high and dangerous.
• Erosion processes


  • Hydraulic action
  • Corrosion
  • Abrasion
  • Attrition
• Erosional landforms


  • Wave cut notches
  • Wave cut platforms
  • Cave-Arch-Stack-Stump sequence
• Longshore drift


  Current flowing along the coast, taking material with it.
• Depositional landforms


  • Beaches
  • Spits
  • Bars
  • Tombolos
  • Cuspate forelands
• Weathering processes


  • Mechanical
  • Chemical
  • Biological
• Mass movement processes


  • Blockfall
  • Rotational slumping
  • Landslides
• Mass movement landforms


  • Rotational scars
  • Talus scree slopes
  • Terraced cliff profiles
• Eustatic sea level change


  Occurs when ice on land melts and returns to the ocean, increasing the volume of water present in the sea.
• Isostatic sea level change

  Occurs from the downward movement of land, causing localised sea level rise.
• Global warming is causing eustatic sea level change as ocean temperatures become warmer and particles expand, taking up more space in the ocean basin. This causes sea levels to rise.
• Tectonic activity


  Can cause sea floor spreading, creating a larger platform for water to sit on. Tectonic activity also contributes to the shape of ocean basins. If the ocean basins get smaller, the volume of the oceans decrease and sea level consequently rises.
• Isostatic sea level change can also be caused by tectonic uplift on plate boundaries, forcing the oceans to be at a higher platform than the land.
• Coastal recession is caused by a mixture of physical and human factors, such as dredging or coastal management.
• There is often a conflict between players: conservationists wish to preserve coastal landscapes whilst businesses may alter natural systems for vested interests. Often the needs of locals are left out of decisions.
• Factors influencing rate of coastal recession

  • Wind direction
  • Tides
  • Seasonality
  • Weather systems
  • Storm occurrence
• Storm surges, tropical cyclones and depressions can cause severe coastal flooding. This has social, economic and environmental implications.
• Climate Change is likely to cause an increase in extreme weather, the frequency and magnitude of storms whilst contributing to sea level rise.
• Consequences of coastal recession and flooding - refer to case studies

  • Economic - Holderness and Tuvalu
  • Social - Holderness and Tuvalu
  • Environmental - Holderness and Tuvalue
• Climate change may cause a rise in environmental refugees from coastal areas, such as those living in Bangladesh and Tuvalu (arguably the most likely countries to face severe flooding).
• Hard engineering techniques


  • Groynes
  • Sea walls
  • Rip rap
  • Revetments
  • Offshore breakwaters
• Soft engineering techniques


  • Beach nourishment
  • Cliff regrading and drainage
  • Beach/dune stabilisation
• Sustainable management aims to meet the needs of today without destroying the needs of the future. Sustainable management is designed to cope with future threats but implementation can cause conflict.
• Integrated Coastal Zone Management (ICZM)


  Regards all aspects of the coastal zone (geographical and political boundaries) in an attempt to achieve sustainability. This creates winners and losers as some can achieve effective management whilst others cannot.
• ICZM techniques


  • Cost-Benefit Analysis
  • Environmental Impact Assessment