coastal landscapes

• wave formation:

  • friction with seabed makes wave height increase and wave length decrease
  • the wave orbit becomes elliptical
  • the swash is the water that rushes up to the beach
  • the backwash is the water that flows back to the sea
• constructive waves:

  • wave crests are far apart
  • they have a gently sloping wave front
  • the breaking wave spills forwards
  • strong swash pushes sand up the beach
  • this forms a gentle beach
  • they are formed by storms hundreds of kilometres away
• destructive waves:

  • wave crests are close together
  • steep front
  • breaking wave plunges downwards
  • strong backwash pulls sand out to sea
  • this forms a steep beach
  • formed by storms close to the coast
• mechanical weathering is physical weathering, which is the break up of rock without any chemical change taking place. for example, water freezing inside a rock, expanding, and cracking the rock (freeze thaw).
• chemical weathering is when the rock is broken down through chemical change, most often acid rain, eg carbonation or solution.
• biological weathering is when animals and plants wear rocks away, for example a plant's roots growing through a rock.
• mass movement is the downward movement of material due to gravity. cliffs collapse to due weathering and gravity, and wave action at the base of the cliff. because the weathered rock is disintegrated away/loose, the cliff falls away.
• types of mass movement:

  rockfall (bits of rock fall off the cliff face, usually due to freeze thaw weathering)

  mudflow (saturated soil flows down a slope)

  landslide (large blocks of rock slide downhill)

  rotational slip (saturated soil slumps down a curved surface)
• hydraulic action is when water is forced into cracks in the rock, compressing the air inside. when the wave retreats, the compressed air blasts out, forcing the rock apart.
• abrasion is when sediment is thrown against the cliff by waves, wearing the cliff away and chipping bits of rock off.
• attrition is when loose sediment knocked off the cliff is swirled around by the water, constantly colliding with other sediment, and getting gradually worn down into smaller and rounder sediment.
• solution is when seawater dissolves material from the rock. it happens along limestone/chalk coasts, when calcium carbonate is dissolved.
• waves come from the sea onto the beach at a 45 degree angle

  eroded material moves along the beach

  gravity causes the sediment to go straight back down the beach to the sea

  A) prevailing wind

  B) direction of longshore drift

  C) swash

  D) backwash

  
• factors which shape our coastline:

  geology - resistant rocks (often forming cliff and headlands), erode slowly. less resistant rocks are easily eroded

  sediment supply

  beach profile - wide beaches protect cliffs more than narrow beaches
• discordant and concordant coastlines

  A) concordant

  B) discordant

  
• headland landforms:

  A) joint or fault in resistant rock

  B) the cave cuts through the headland to make an arch

  C) hydraulic action and abrasion widen it to form a cave

  D) the arch becomes too heavy and collapses

  E) this leaves a tall stack

  F) the stack is eroded, forming a stump

  
• beaches are mainly formed by constructive waves. deposition occurs in sheltered areas where the build up of sand and shingle is greater than its removal. sandy beaches have gently sloping profiles, shingle and pebble beaches are steeper
• a storm beach is formed when, at the back of the beach, a very strong swash during storm conditions may deposit larger material.
• berms are smaller ridges at the position of the mean high tide, resulting from deposition at the top of the swash of smaller waves, with smaller material.
• dunes formation:

  sand is deposited at the back of the beach by the swash and wind

  embryo dunes form around an obstacle, such as rocks

  over time, these become colonised by vegetation

  these dunes become fore and yellow dunes

  marram grass colonises fore dunes and the roots stabilise the dunes

  ponds may form in dune stacks created by hollows formed by the wind

  a wider variety of plants colonise the back dunes
• spit formation:

  long shore drift carries eroded material down the beach

  where the coastline changes direction, the sea deposits eroded material

  the end of the spit gets curved by wave action

  a bar farms when a spit crosses from one headland to another, enclosing the bay

  
• sea walls are curved concrete walls at the foot of a cliff, to prevent erosion. they are effective, but expensive at £2000 per metre.
• rock armour is large boulders at the foot of a cliff, the are cheap and easy to maintain, but they are unattractive.
• gabions are rocks held in place by mesh cages. they are cheap and absorb wave energy, but they are not very strong and look unnatural.
• groynes are wooden or rock structures built out at right angles into the sea. they build a beach and trap sediment, but are unattractive.
• beach nourishment is when sand is pumped onto a beach to build it up. it blends in with existing beach, however it needs to be replaced constantly and the sand has be taken from somewhere else.
• reprofiling is when sediment is moved from the lower to the upper part of the beach. it is cheap and simple but needs to be repeated continuously.
• dune nourishment is when marram grass is planted on sand dunes to stabilise them. it is cheap and natural, but they can be damaged by storm waves.
• coastal defences on North Norfolk coastline:

  happisburgh is located on the coast of south east England. highly destructive waves are eating away at the coastline at 40ft per year, destroying houses

  rock armour was placed at the foot of the sea wall

  sand was added to the beach to widen it