Coast

• Fetch: distance that waves have travelled to a coastline
• Coast: where land meets the sea
• Constructive waves: short, long wavelength, flat & gentle, low frequency, strong swash , weak backwash, caused by distant storms

  [Deposition]
• Destructive waves: taller, short wave length, steeper, high frequency, weak swash, strong backwash [Erosion]
• Longshore drift: process of transporting material along the coast

  
• Swash: pushes material up beach
• Backwash: Scours beach, pulling sand back beach
• Spits: spits are formed by the process of longshore drift, swash carries material along the coast. Backwash takes material back and carries everything, forming at the end. Deposition being carried away, changing the coast, curving it depending on the wind direction to form a spit.
• Headland and bays: formed by bands of rock of different levels of resistance, existing next to each other perpendicular to the sea, this causes softer rocks to be eroded more quickly by processes such as abrasion creating a bay. These bays became sheltered by headlands meaning beaches are built up by constructive waves.
• Wave cut platforms: The waves attack the base of the cliff through erosion, over-time the clidd will be undercut and a wave cut notch is formed, eventually the cliff will collapse, further cliff retreat will form a wave-cut platform
• 1. large crack opened up by hydraulic action
  2. crack grows into a cave by hydraulic action
  3. cave becomes larger
  4. cave breaks through the headland forming a natural arch
  5. arch is eroded and collapses
  6. leaving a full rock stack
  7. stack is eroded turning into a stump
• Sand dunes form where obstacles lay on the beach, sand is blown onto beach to form dunes

  
• Coral reefs: created by polyps, create food and energy for corals, has a symbiotic relationship with coral

  conditions = shallow water, clear, warm, unpolluted, sheltered
• Mangrove forests:

  location: tropical and subtropical latitudes near equator, near corals and in sheltered areas

  why roots exposed: they need access to air and oxygen

  why important: reduce erosion and absorb storm surge, protect coastline

  why threat: have been deforested to make way for rice paddies, palm oil, etc

  conditions: high salinity, between high & low water mark, gentle wave action, sheltered area, tropical & subtropical latitude, low shore gradient, temp of water 20+ in cold month

  characteristic: shiny green leaves, packed tightly, aerial roots, grow in shallow muddy water
• Opportunities and hazards to living near coast:

  O - Tourism, recreational activities, job opportunities

  H - Do nothing, Hold the line, Retreating the line, Advancing the line
• Holderness:

  1. Beach replenishment at Withersea (transporting sand onto an eroding shoreline to widen the existing beach) 
  2. Sea wall at Bridlington 5 km (A wall curved outwards to deflect the power of the waves
  3. Rock groynes 2 at Mappleton (trap sediment from longshore drift
• Soft engineering:

  1. Beach replenishment: Transporting sand back onto a beach to replace eroded material A - Beaches absorb wave energy D - Has be repeated regularly which is expensive
  2. Managed retreat: Existing coastal defences are abandoned allowing the sea to flood inland until it reaches higher land A - No expensive construction costs D - Disruptive to people where land and homes are lost
• Hard engineering

  1. Sea wall: A wall curved outwards to deflect the power of the waves A - Prevents erosion and flooding D - Expensive to build
  2. Groynes: Wood built at right angles to the shore, which traps beach material being moved by longshore drift A - Slows erosion D - Stops material moving down the coast
  3. Gabions: Wire cages filled with stone, etc A - Cheap D - Wire cages can break
  4. Rip-rap: Big boulders piled to protect coast A - Cheap D - Boulders can erode or dislodge during storms
  5. Revetments: Sloped fence with an open plank structure A - Break force of wave D - Useless in storms
• Hydraulic action: when air gets trapped in cracks and gets compressed, the power of breaking waves causes it to erode
• Abrasion: when waves pick up rocks and other material and throws it onto a coastline, this causes parts of the cliff to dislodge,
• Attrition: wearing away of rock, usually causing small and rounded pebbles
• Solution: when weak acid in the water dissolves minerals in the rocks
• Why retreat the line:

  • doesn't pose too much a threat to infrastructure and people
  • cost of protection (engineering strategies) is expensive
  • protection in one area may cause problems somewhere else
  • may damage natural landscape and ecosystem