Coasts

• Backshore


  The area between high watermark and the landward limit
• Foreshore


  The area between the high water mark and the low water mark
• Nearshore


  The area between the low water mark and the point where the waves don't really have any influence
• Offshore


  The point beyond where the waves cease to impact upon the seabed
• Coast should be seen as a system with flows, inputs and stores
• Inputs to the coastal system

  • Wind
  • Waves
  • Sea currents
  • Tides
• Wave movement at the beach

  • Friction within the seabed slows down the wave
  • Wave crest continues to move forward
  • Elliptical orbit of wave
  • Wave gets steeper before rushing up the beach as swash and returning as backwash
• Constructive waves


  Low wave height, low frequency, weak backwash but strong swash
• Destructive waves


  Higher wave height, higher frequency, powerful backwash
• Wave refraction


  1. Waves bend towards shallower water

  2. Quicker the change in water depth, the quicker the refraction
• Longshore drift


  Sediment is pushed up the beach at an angle by the prevailing wind and waves, then dragged back out to sea
• Rip currents


  Strong currents that move away from the shoreline
• Tide


  Periodic rise and fall of the sea level
• Spring tide


  Tide just after new or full moon
• Neap tide


  Tide just after the first or third quarters of the moon
• Tidal range


  Difference between high and low tide
• Macro


  Large scale
• Micro


  Extremely small scale
• High energy coastline


  Wave energy is high, erosion is likely to be greater
• Low energy coastline


  Wave energy is typically lower, deposition is normally greater
• Marine processes


  • Erosion
  • Transportation
  • Deposition
• Sub-aerial processes


  • Weathering
  • Mass movement
• Simple spit


  Spit that goes out roughly parallel to the coast
• Compound spit


  Spit with occasional changes in the dominant wind process, resulting in a hooked or curved feature
• Bar


  Ridge of sand and shingle which joins up to headlands, often cutting off a bay behind which a lagoon is found
• Mud flats


  Found at the edges of permanently submerged marine zones, susceptible to changes in sea level, wave action, volume of water in the river and tidal flows
• Salt marshes


  Develop from mud flats in sheltered shorelines with a river estuary, salt water, and fine sediment, where the flow of the river and sea meet
• Eustatic sea level change

  Caused by volume of water in the sea or by the change in the shape of the ocean basin
• Isostatic sea level change

  Caused by vertical movements of the land relative to the sea
• Submergent coastline


  Stretches along the coast that have been inundated by the sea due to a rise in sea level
• Emergent coastline


  Coast that has been exposed due to a fall in sea level
• Raised beaches


  Areas of sand or shingle deposits found high above the current sea level
• Aims of coastal management

  • Provide defense against flooding
  • Provide protection against coastal erosion
• Shoreline management plan


  Developed as part of the UK government's efforts to make coastal management more sustainable, covering 22 sediment cells
• Shoreline management options


  • Hold the line
  • Manage realignment
  • No active intervention
  • Advance the line
• Integrated coastal zone management


  Integrates and views the environment as a whole, considering different uses of the area and involving local, regional and national authorities
• The Sundarbans is the world's largest mangrove forest, facing risks from climate change, industrial projects, and destructive fishing
• Approaches to managing risks in the Sundarbans

  • Develop resilience
  • Mitigation
  • Adaptation