coasts

• Coastal system


  An open system that receives inputs from outside and transfers outputs away from the coast into other systems
• Coastal system includes the rock, water and carbon cycles
• Closed system


  How the coastal system is considered in some circumstances such as during scientific research and coastline management planning
• The coastal system is impacted and impacts upon processes which occur in the five oceans of our planet and the smaller seas of which they are part of
• Habitats and activities affected by and affecting the coastal environment

  • Sediment Cells
  • Prominent Headlands
  • Sediment Movement
  • Dynamic Equilibrium
• Sediment cell


  Sections into which coasts can be split, often bordered by prominent headlands, where the movement of sediment is almost contained
• Dynamic equilibrium


  The maintenance of a balance in a natural system, despite it being in a constant state of change, where inputs and outputs constantly change to maintain the balance
• Dynamic equilibrium may be upset in the long term by human interventions, or in the short term it may be interrupted by natural variations
• Key features of the coastal system

  • Inputs
  • Outputs
  • Stores/Sinks
  • Transfers/Flows
  • Energy
• Inputs


  Material or energy inputs including marine (waves, tides, salt spray), atmospheric (sun, air pressure, wind) and human (pollution, recreation, settlement, defences)
• Outputs


  Material or energy outputs including ocean currents, rip tides, sediment transfer, evaporation
• Stores/Sinks


  • Beaches
  • Sand Dunes
  • Spits
  • Bars and Tombolos
  • Headlands and Bays
  • Nearshore Sediment
  • Cliffs
  • Wave-cut Notches
  • Wave-cut Platforms
  • Caves
  • Arches
  • Stacks
  • Stumps
  • Salt Marshes
  • Tidal Flats
  • Offshore Bands and Bars
• Transfers/Flows


  • Wind-blown sand
  • Mass-movement processes
  • Longshore drift
  • Weathering
  • Erosion (hydraulic action, corrosion, attrition, abrasion)
  • Transportation (bedload, in suspension, traction, in solution)
  • Deposition (gravity settling, flocculation)
• Energy sources


  • Wind
  • Gravitational
  • Flowing Water
• Positive feedback loop


  Mechanisms that exaggerate changes, making the system more unstable and taking it away from dynamic equilibrium
• Negative feedback loop

  Mechanisms that balance changes, taking the system back towards equilibrium
• Sediment sources

  • Rivers
  • Cliff erosion
  • Wind
  • Glaciers
  • Offshore
• Longshore drift

  Sediment moved along the beach due to prevailing winds altering the direction of the waves
• Sediment budget


  Data of inputs, outputs, stores and transfers used to assess the gains and losses of sediment within a sediment cell
• Littoral zone

  The area of land between the cliff's or dunes on the coast and the offshore area that is beyond the influence of the waves, constantly changing due to short-term and long-term factors
• Shore/Shoreline


  The boundary between the sea and the land
• Offshore


  The area beyond the influence of waves
• Onshore

  The area of land not covered by the sea, but very close to it
• Wave formation

  Wind moving across the surface of the water causes frictional drag, creating small ripples and waves with a circular orbital motion of water particles, which becomes more elliptical as the seabed becomes shallower, leading to more horizontal movement and increased wave height
• Factors affecting wave energy

  • Strength of the wind
  • Duration of the wind
  • Size of the fetch
• Constructive waves

  Tend to deposit material, creating depositional landforms and increasing the size of beaches
• Destructive waves

  Act to remove depositional landforms through erosion, decreasing the size of a beach
• In summer, constructive waves dominate but destructive waves dominate in winter
• Constructive waves may become destructive waves if a storm begins
• Climate change may increase the storm frequency within the UK
• Coastal management may affect the type of waves that occur
• Presence of constructive waves

  Causes deposition on the beach, leading to a steeper beach profile which favours the formation of destructive waves
• Presence of destructive waves

  Erodes the beach, reducing the beach profile and leading to the formation of constructive waves
• Tides


  Changes in water levels caused by the gravitational pull of the sun and moon, with the highest high tide and lowest low tide (spring tide) occurring when the sun and moon are aligned, and the lowest high tide and highest low tide (neap tide) occurring when the sun and moon are perpendicular
• Rip currents


  Powerful underwater currents occurring in areas close to the shoreline, caused by a buildup of water at the top of the beach forcing the backwash under the surface
• High-energy coastlines


  Associated with more powerful waves, rocky headlands and landforms, and frequent destructive waves, often eroding as the rate of erosion exceeds the rate of deposition
• Low-energy coastlines


  Associated with less powerful waves, sheltered areas with constructive waves, sandy areas, and depositional landforms as the rate of deposition exceeds the rate of erosion
• Wave refraction


  The process by which waves turn and lose energy around a headland on uneven coastlines, with wave energy focused on the headlands and dissipated in bays
• Wave refraction leads to the formation of erosive features on headlands and depositional features in bays
• Erosion leading to headlands and bays

  Increases erosion on the headlands and reduces erosion in the bays, eventually wearing away the headlands and increasing erosion in the bays, leading to dynamic equilibrium