systems and processes in coastal environments

Cards (96)

  • fetch - the distance the wind has travelled
  • swash - the wave moving up the beach
  • backwash - the wave moving out
  • Constructive waves - adding sediment to the beach
  • Destructive - removal of sediment from the beach
  • prevailing winds - most dominant wind direction
  • erosion - breaking down of material and the removal of it
  • discordant coastline - perpendicular to the sea, mixture of hard and soft rock
  • Concordant coastline - parallel to the sea and the same rock type
  • long shore drift - movement of sediment along the coastline, by swash and backwash
  • Coastal system
    • open system
    • a series of linked elements affecting the coastal zone through which energy and material circulate
    • dynamic interface where the land and the sea meet
  • coast - part of the land near the sea; edge of the land
  • coastline - regarded as an open system, with inputs, processes and outputs; interacts with the surroundings
  • sand supply
    • sand is food for beaches and gives shorelines protection from waves
    • being starved of sand can cause increased rate of erosion
  • waves:
    • the erosive action of a wave increased when the wave is high
    • the angle at which they strike and how much sand they are carrying can also influence the rate of erosion
  • Factors affecting the coastline:
    • wave type
    • rock type
    • fetch
    • climate
    • agents of erosion
    • sea level change
    • sediment type
    • topography
  • landform - a specific geomorphic feature on the surface of the earth, ranging from large scale features such as plains, plateaus and mountains to minor features such as hills, valleys and alluvial fans
  • landscape - part of the earths surface that can be viewed at one time from one place. It consists of geographic features/landforms that are characteristics of a particular area
  • inputs - human activity, sediment, relief, waves, tides, current, rocks, sediments and changes in sea level
    processes - erosion, long shore drift and deposition
    outputs - arches, stacks, beach, spits, salt marshes, cliffs, sand dunes and loss of wave energy
  • inputs of energy at the coast:
    • wind
    • waves
    • tides
    • sediment
    • human activity
  • wind
    • wind moves from high to low pressure
    • variations in atmospheric pressure is caused by differences in surface heating by the sun
    • the grater the pressure difference the stronger the wind
  • roles of wind in coastal system:
    • prevailing wind
    • creation of waves
    • agent of erosion
  • factors affecting wave energy:
    • strength of the wind
    • duration of the wind
    • fetch
    • prevailing wind
  • UK prevailing winds
    • come from the south-west, the results from air moving from sub-tropical high pressure belt at 30 degree north to the sub-polar low pressure belt at 60 degree north.
    • wind blows across Atlantic ocean
  • Wave formation:
    • waves are formed by wind moving over the ocean
    • as the wind drags over the surface, friction causes disturbance and causing waves
    • In open water, waves have orbital motion
    • as they approach the land this motion is interrupted by friction with the sea bed to become elliptical in shape
    • this reduces wave length and increases wave height
    • when the height to length ration reaches 1:7 the wave breaks
    • the breaking of a wave causes swash
    • when water has no energy left the water runs back down the beach under gravity as backwash
  • Wave period - how long it takes two crests to pass a certain point
  • wave frequency - the number of waves passing a certain point per minute
  • constructive waves
    • causes deposition of material
    • decreased frequency
    • decreased height
    • increased wavelength
    • strong swash and weak backwash
    • created a berm
    • small, gentle waves
  • destructive waves
    • removal of sediment
    • weak swash and strong backwash
    • high steep waves
    • base of cliff attacked
    • shorter wavelength
    • increased height
  • Wave refraction
    • when waves approach an irregular shaped coastline, then waves are refracted
    • wave fronts can become distorted which can distort the spread of energy
    • as the wave nears the coastline it is slowed by friction in the shallower water off the headland causing waves to increase in height
  • wave refraction
    • wave energy becomes concentrated on the headland, causing greater erosion. The low energy waves spill into the bay, resulting in beach deposition
    • the part of the wave crest in the deeper water approaches bay fast as not slowed by friction. waves bend around the headland and the orthogonal converge.
    • the low energy waves spill into the bay resulting in beach deposition, this caused a long shore drift movement
  • swash aligned beach
    • waves break parallel to the shore. No long shore movement of sediment once the equilibrium form is established.
  • drift aligned beach
    • sediment inputs are sufficient to meet the demand for long shore drift
    • beach progrades to become parallel to the line of maximum drift
  • Tides - the periodic rise and fall of the level of the sea in response to the gravitational pull of the sun and moon
  • tides:
    • moon pulls water towards it, creating a high tide
    • the draining of water from the intertwining areas between these bulges causes low tides
  • spring tide - when the moon is between the earth and the sun, the combined gravitational pull creates the biggest bulge of water and highest tide. Tidal range = greatest
  • neap tide - when the earth, moon and sun form a right angle, their gravitational pull interfere with one another and this is where the near tide occur, giving the lowest high tides and highest low tides. Tidal range = smallest
  • tidal ranges determine the upper and lower limits of erosion and deposition and the amount of time each day hat the littoral zone is exposed and open to aerial weathering
  • high energy coastlines:
    • tend to be rocky coastlines
    • tend to be stretches of the atlantic facing coast
    • the rate of erosion exceeds deposition
    • landforms: headlands, cliffs and wave-cut platforms
  • low energy coastlines:
    • tend to be sandy coasts
    • stretches of the coast where the waves are less powerful
    • rate of deposition exceeds erosion
    • landforms; beaches, spits and coastal plains