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• A system is a set of interrelated objects comprising components (stores) and processes (links) that are connected to form a working unit or unified whole.
• The energy available to a coastal landscape may be kinetic, potential or thermal. This energy allows work to be carried out by geomorphic processes.
• Coastal landscapes are recognised as being open systems. This means energy and matter can be transferred from neighbouring systems as an input. It can also be transferred to neighbouring systems as an output.
• Inputs include:

  1. kinetic energy from wind
  2. Thermal energy from heat from sun
  3. Potential energy from position of material on slopes
  4. Material from marine deposition, weathering and mass movement
• Outputs include:

  1. Marine and wind erosion.
  2. evaporation
• Throughputs include:

  1. stores such as beach and nearshore sediment accumulations
  2. flows such as longshore drift
• When a system's inputs and outputs are equal , they are in a state of equilibrium

  When equilibrium is disturbed , the system goes through self-regulation to restore this equilibrium. This is known as dynamic equilibrium.
• A sediment cell is a stretch of coastline and its associated nearshore area within which the movement of coarse sediment, sand and shingle is largely self-contained
• A sediment cell is regarded as a closed system. The boundaries are determined by the topography and shape of the coastline.

  Large natural barriers (e.g Headlands) prevent movement of sediment.
• Variations in wind direction and the presence of tidal currents means it is inevitable that some sediment is transferred between cells
• Wind:

  Wave energy is generated by the frictional drag of wind moving across ocean surface

  The higher the wind speed and the longer the fetch , the larger the waves and the more energy they possess.

  If they blow at an angle to the coast , the waves will approach at an angle and generate longshore drift

  It can carry out erosion , transportation and deposition itself (aeolian processes)
• Waves energy formula:

  P = H^2T

  P = Power (kilowatts) per metre of wave front

  H = Wave height (metres)

  T = Wave period (seconds) the time interval between wave crests
• Wave anatomy:

  Crest - highest surface part of a wave

  Trough - Lowest part of a wave

  Wave height - vertical distance between the crest and trough

  Wavelength - distance between 2 adjacent crests or troughs
• Swell waves are waves formed in open water have a long wavelength with a wave period up to 20 seconds

  Storm waves typically have a short wavelength , greater height and shorter wave period
• Breaking waves:

  Wave moves into shallow water (half the wavelength)

  Deepest circling water molecules come into contact with seafloor

  Friction between them changes the speed , direction and shape of waves

  Waves slow down , wavelength decreases and waves bunch up

  Deepest part of the wave slows down more than top of wave

  Crest advances ahead of base

  When wave depth is less than 1.3 x the wave height , the wave breaks

  It is at this point there is a significant movement of water as well as energy
• Spilling waves - Steep waves breaking onto gently sloping beaches , water spills gently forward as the wave breaks
• Plunging - Moderately steep waves breaking onto steep beaches , water plunges vertically downwards as the crest curls over
• Surging - low-angle waves breaking onto steep beaches , the wave slides forward and may not actually break
• Waves move up the beach as swash driven by energy from the breaking of the waves

  friction and gradient of beach decreases speed

  Water then gets drawn back in as backwash (movement comes from gravity and always occurs perpendicular to coastline)
• Constructive waves:

  • Low in height
  • Long wavelength
  • Low frequency (6 - 8 per minute)
  • Usually break as spilling waves
  • Swash is stronger than backwash
• Destructive wave:

  • Greater height
  • shorter wavelength
  • Higher frequency (12 - 14 per minute)
  • Usually break as plunging waves
  • Backwash stronger than swash (swash is slowed down by backwash of the previous wave due to short wavelength)
• High-energy waves remove material from top of beach, reducing beach gradient

  Low-energy waves build up the beach face, steepening the profile
• Tides are the periodic rise and fall of the sea level caused by the gravitational pull of the moon and sun.
• The moon pulls water towards it, creating a high tide with a compensatory bulge on the opposite side. There is low tide between the bulges
• Spring tides occur when the Sun, Moon and Earth align, causing greater tidal range
• Neap tides occur when the Sun, Moon and Earth form an angle of approximately 90 degrees, resulting in smaller tidal ranges
• Tidal range influences where wave action occurs and the weathering processes that occur on the land exposed between tides.
• Lithology describes the physical and chemical composition of rocks.
• The structure of rocks is the properties of that individual rock type such as jointing, bedding and faulting . It also includes the permeability of rocks.
• Rock outcrops that are uniform or run parallel to the coastline tend to produce straight coastlines known as concordant coastlines
• If rock outcrops lie at right angles to the coast they create a discordant coastline
• Structure of rocks can also influence cliff profiles.

  Horizontally bedded and landward - dipping strata support cliffs with steep, vertical profiles.

  Seaward dipping strata tend to create cliff profiles which tend to follow the angle of dip of the bedding planes
• Rip currents are caused by tidal motion or waves breaking at right angles to the shore. They modify the shore profile by creating cusps which help perpetuate the rip current.
• Ocean currents are generated by the rotation of the earth and by convection and set in motion by the movement of wind over the water surface.
• warm ocean currents transfer heat energy from low latitudes towards the poles . Cold ocean currents do the opposite

  The strength of the current itself will have limited effect on coastal landscape systems but the transfer of heat energy is significant as it affects air temperature and therefore sub-aerial processes.
• Terrestrial sources of sediment:

  1. Rivers are major sources of sediment input to the coastal sediment budget. In some areas, as much as 80% of coastal sediment comes from rivers .
  2. Wave erosion is also a large source of sediment . The erosion of weak cliffs in high energy environments can contribute to as much as 70% of the overall material supplied to beaches
  3. Longshore drift can also supply coastal sediment by moving sediment along the coast from one area to another
• Offshore sources of sediment:

  1. Constructive waves bring sediment from offshore locations and deposit it. Tides and currents also do the same
  2. Wind blows sediment from other locations including sand bars, dunes and beaches. This material is typically fine sand as wind does not have as much energy as water
• Human sources of sediment:

  1. Beach nourishment is used to help maintain sediment equilibrium
  2. Lorries can bring sediment and dump it on the beach which is then spread out by bulldozers
  3. Sand and water can be pumped onshore from offshore sources, then the water is drained away leaving the sediment behind.
• By subtracting the amount of sediment lost from the amount of sediment gained, it can be determined if the sediment budget is in surplus, deficit or equilibrium
• Weathering uses energy to produce physically or chemically altered materials from surface or near surface rock.