Coastal landscapes and change

• factors that affect sediment transportation

  
  

  (energy provided by the waves, tides, and currents transports eroded material)

  • wave actions create and destroy most landforms
  • tides affect the position in which waves break on the beach
  • higher the tidal range the more powerful the currents will be
• transportation processes

  • solution - dissolved substances carried in the water
  • suspension - very fine material e.g slit whipped up by turbulence and carried along the water (most material carried this way)
  • saltation - larger particles such as pebbles that are too heavy for suspension to carry them, bounce along the sea bed from the force of the water
  • Traction - very large particles like boulders are pushed and rolled along the sea bed by the force of the water
• Longshore drift - transports sediment along shore:

  • swash - carries sediment up the beach parallel to prevailing wind
  • Backwash - carries sediment back down the beach at right angles to the shoreline
  • when there's an angle between the prevailing winds and the shoreline, backwash and swash move the sediment along the shore in a zigzag pattern
• beaches

  • beaches form from constructive waves that deposit sediment on shore
  • natural sorting - large sediment at the top of the beach and smaller sediment closer to the shore. this is due to swash depositing all material but the backwash limits where it goes based on its energy
  • berms - ridges of sand and pebbles standing 1-2m high which occur at high tide mark
  • runnels - parallel to the shore which forms when backwash drains back to sea
  • cusps - crescent-shaped indentations created by constructive waves approaching the beach at an angle
• deposition occurs when waves lose the ability to transport sediment. this may be due to reduced water volume or reduced water velocity which means it has less energy to transport sediment. larger pieces of sediment are deposited first then smaller.
• Spits

  • tend to form when the coast changes direction e.g. across river mouths
  • longshore drift continues to deposit across the river mouth leaving a bank of sediment sticking out into the sea
• types of spits

  • simple spits - straight lines which grows parallel to the coast
  • recurved spit - occasional changes to dominant wind and wave direction cause a curved end
  • compound split - if the wave returns to original direction longshore drift abandons the recurved spit and the spit continues to grow straight which causes multiple recurved spits
• spits

  • the area behind the spit is sheltered from waves which can then develop into saltmarshes and mudflats
  • cuspate forelands- occurs when two spits form in different directions and merge into a low lying triangular shape
  • double spit - occur on opposite ends of a bay both extending towards its middle. the outflow of river discharge stops the two spits from joining.
• bars and tombolo's

  • bars - formed when two spits join together (occurs across bay/river mouth)
  • lagoon - forms behind the bar as seawater is trapped. over time if there is a stream flowing into this, the water can become less saline
  • offshore bars - when a bar forms off the coast when the material moves towards the shoreline and they may remain partly submerged by the sea
  • tombolo- when a bar connects the shore to an island/stack and can also be formed by wave refraction occurring around an island
• barrier beaches

  • long narrow island of sand that run parallel to the shore and detach from it. form from areas with fairly powerful waves and a small tidal range
• what does vegetation do to deposited material?

  stabilises the material which protects it from wind and waves
• succession

  • the process by which an ecosystem changes over time
  • smaller pioneer species colonise an area of bare sediment, die and decompose which then creates a basic soil
  • conditions become less hostile meaning new organisms can grow
  • overtime complex plant structures can grow like trees
  • final plant species in the succession are called the climatic climax community of plants
• Sand dunes

  • form when longshore drift deposits material which is transported up the beach by the wind.
  • sand is trapped by driftwood or berms which is colonised by pioneer species such as crouch grass or marram grass
  • the vegetation stabilises the sand and encourages more sand to accumulate there which forms embryo dunes
  • older dunes occur further inland as newer embryo dunes dorm closer to the shore
• mudflats and saltmarshes form in sheltered places and low energy environments by a process called flocculation
• littoral zone


  • boundary between land and sea
  • stretches onto sea and shore
  • zone not a line
  • short term factors - individual waves, daily tides, and seasonal storms
  • long term factors - changes to sea levels or climate change
• rock types


  • sedimentary - limestone, formed in strata, jointed sedimentary rocks are permeable, chalk sedimentary rocks are porous
  • igneous - graphite, crystalline, resistant, and impermeable
  • metamorphic - marble, very hard, impermeable, resistant
  • unconsolidated materials - loose like a bolder, cemented together, easily eroded
• types of coastlines


  • concordant coastline- where the tpye of rock runs parallel to the coast
  • discordant coastline - where the type of rock runs perpendicular to the coast
• factors that influence the rates of coastal recession


  • concordant/discordant coastline
  • geological structures'
  • geology
  • cliff profiles
• types of waves


  • constructive - limited backwash, sediment deposited by waves
  • destructive - sediment pulled to sea by backwash
• seasonal beaches


  • summer beaches - constructive waves provide sediment, beach profile steeper
  • winter beaches - destructive waves erode sediment, plunging wave
• types of erosion


  • hydraulic action - eroded a crack
  • abrasion - break base of the cliff
  • attrition - wear down rocks
  • solution - disolves the rock with acids in the seawater
• transportation


  • traction
  • saltation
  • suspension
  • solution
• weathering


  • chemical
  • physical
  • biological
• mass movement


  • rock fall
  • mud flow
  • slumping
• coastal erosion landforms


  • fault/notch, cave, arch, stack, stump
  • wave cut notches
  • wave cut platforms
• landscapes and systems


  • rock coast - high energy coastline - headlines and cliffs- weathering and erosion
  • sandy and estuarine - low energy coastline - beaches and pits - transportation and deposition
• coastal depositional landforms


  • longshore drift
  • spits
  • beaches - swash aligned or drift aligned
  • offshore bars
  • barrier beaches(bars)
  • tombolo's
  • cuspate foreland
• salt marshes - stabilises the beach
• sediment cells - moves along the coastline in sediment cells, within each cell sediment moves between beaches, cliffs, and the sea through the process of erosion, transportation, and deposition
• • sediment budget - the amount of sediment available within a sediment cell
  • positive feedback - sediment budget falls, wave continues to transport sediment
  • negative feedback - sediment budget increases, more deposition
• • subaerial processes - mass movement and weathering
• examples of weathering


  mechanical

  • freeze thaw
  • salt crystallisation
  • wetting and drying

  chemical

  • carbonation
  • hydrolysis
  • oxidation

  biological

  • plant roots
  • rock boring
  • animals
• examples of mass movement


  • fall
  • topple
  • translational slide
  • slumping
  • flow
• • eustatic change - when there is a rise or fall in sea level by a change in volume of water. this is global change affecting all the worlds connected seas and oceans
  • isostatic change - a local rise or fall in land level (isolated areas)
• • submergent coasts - coastline that were not affected by glacial ice cover, the post glacial sea level rise has created submergent coastlines
  • emergent coastlines - created by a fall in sea level
• emergent landforms


  • raised beaches - (FIFE, SCOTLAND)
  • fossil cliffs - (Ayrshire, Scotland)
• submergent landforms


  • rias - (KINGSBRIDGE ESTUARY , ENGLAND)
  • fjords - (MILFORD SOUND , NEW ZEALAND)
  • Dalmatian coastlines - ( DALMATION COAST, CROTIA)
• Kiribati


  • a group of islands in the central pacific ocean which consists of 33 widely spaced islands
  • 2014 - purchase of 20km of land in one of the Fijian islands to be used for refuge
  • many of the islands will disappear in the next 50 years
  • some places sea level rises 1.2cm a year
• Holderness coastline


  • geology - boulder clay (weak), produces shallow sloping cliffs between 5 and 20 metres high
  • influence fetch, wave size and tides - exposed to widns, sea floor relatively dep