coasts

• how waves are formed

  • caused by winds blowing over the winds surface
  • friction on the water causes ripples
  • wind continus blowing till a circular orbit is created
  • as the water become more shallow the circular orbit is distorted and the orbits become more eliptical and taller and steeper
• factors that affect storm

  • how shallow and deep the ocean is
  • wind
  • fetch ( how far the wave travels )
• constructive waves

  • long distance between each wave
  • wave height is low and small
  • strong swash
  • weak backwash
  • waves have low energy due to gentle winds
• processes that change coastlines

  • coastal weathering
  • mass movement
  • erosion
• coastal weathering

  • ( mechanical ) freeze-thaw weathering
  • ( chemical ) acid rain
• mass movement

  • landslides
  • rotational slip ( saturated soil and clays slump down)
  • rock fall
• erosion

  • abrasion
  • attrition
  • hydraulic action
• deposition occurs in bays and sheltered areas
• longshore drift is the movement of sediment along the coast
• concordant coastline

  • band of rocks lay parallell to the coastline
  • one continuous layer of the same rock
• discordant coastline

  • band of resistant and less resistance rocks that lie perpendicular in alternate layers
• sand dunes need

  • large flat beach
  • large supply of sand
  • large tidal range
  • onshore wind
  • obstacle
• spits are long ridges of sand which stick out rom the land which are formed by deposition and longshore drift
• how do spits form

  • longshore drift continues to transport material in the direction of prevailing wind and deposit out to sea
  • sediment build up and form a spit
  • the end curves and a salt marsh develops behind
• bars are formed when a spit extends across a bay and connect two headlands
• bars sometimes create lagoons which is a lake trapped behind the ridge of sand
• dorset coast is found in the south coast of england
• groynes

  • structures built out to sea to trap sediment being moved by longshore drift and help widen the beach
  • + wide beach so it acts as a buffer
  • + useful structures for fishing
  • -increases rate of erosion elslewhere
  • -looks unnatural
• sea walls

  • concrete or rock barrier against the sea
  • + very effective
  • + makes a walkway
  • + durable and longlasting
  • -can look unnatural
  • -expensive and has high maintenance costs
• rock armour

  • large boulder of rocks
  • + cheap
  • + effective
  • + used for fishing
  • -taken from other parts of the coast
  • -expensive to transport
  • -obstrusive
• gabions

  • caged filled with rocks
  • + cheap
  • + improves drainage
  • + encourages vegetation
  • -looks unnatural
  • -lasts 5-10 years
• beach nourishment

  • adding sand to the beach to make it wider
  • -needs constant maintaining
• dune regeneration

  • planting marram grass
  • -easily damaged and time consuming
• beach reprofiling

  • shape of the beach is changed
  • -frequent maintaining
  • -only for low impact waves