Rivers and Coasts

• Destructive Wave

  Has a weak swash and strong backwash

  Strong backwash removes sediment from the beach

  Waves are steep and close together

  High frequency
• Constructive Waves

  Strong swash and weak backwash

  Strong swash brings sediment to build up the beach

  Backwash is not strong enough to remove the sediment

  Waves are low and far apart

  Low frequency
• Freeze-thaw weathering 


  Water enters cracks in the rock

  When temperatures drop the water freezes and expands causing the crack to widen

  The ice melts and water makes its way deeper into the cracks

  The process repeats itself until the rock splits entirely
• Biological weathering 


  Plant roots can get into small cracks in the rock

  As the root grows, the cracks become larger causing small pieces of rock to break away
• Chemical weathering 


  Rain and sea water can be slightly acidic

  If a coastline is made up of rocks like limestone and chalk over time they can be dissolved by the acid
• Mudflow


  Type of mass movement where saturated soil flows down a slope
• Rotational slip 


  Type of mass movement where saturated soil slumps down a curved surface
• Abrasion 


  When pebbles grind along a rock platform, much like sandpaper

  Over time the rock becomes smooth
• Attrition

  When rocks knock against each other

  They break apart to become smaller and more rounded
• Solution (erosion)


  When certain types of rock are dissolved into the water

  Chalk and limestone cliffs are prone to this
• Solution (transportation)


  When minerals in rocks are dissolved in sea water and then carried

  Invisible load
• Suspension

  Small particles like silt and clay are suspended in the flow of the water
• Saltation 


  Where small pieces of shingle or large sand grains are bounced along the sea bed
• Traction 


  Where pebbles and larger material are rolled along the bed
• Factors leading to deposition include..

  Waves starting to slow down and lose energy

  Shallow water

  Sheltered areas like bays

  Little to no wind
• Deposition 


  Where the sea loses energy and drops carried material

  Occurs in constructive waves
• Beach reprofiling 


  Soft engineering

  Sediment is redistributed from the lower part of the beach to the upper part of the beach
• Beach nourishment 


  Soft engineering

  Beaches are made higher and wider by importing sand and shingle to an area affected by longshore drift to increase its height and width to provide protection from erosion or flooding by absorbing wave energy
• Managed retreat 


  Soft engineering

  Controlled flooding of low-lying coastal areas in an area that is at high risk of erosion

  Usually occurs where the land is low value like farm land
• Rock armour / rip rap

  Hard engineering

  Barrier of large boulders placed in front of a cliff or sea wall to absorb wave energy
• Gabion baskets 


  Hard engineering

  Rocks held in mesh cages and places in areas affected by erosion

  Water enters the cages and wave energy is absorbed and dissipated
• Dune stabilisation 


  Soft engineering

  Marram grass is planted to stabilise the dunes and helps trap sand to build them up
• Meandering rivers flow through wide floodplains with gentle gradients

  They often change course over time as they cut downwards into their valley floor
• Deltas are formed where a river meets another body of water

  They empty their water and sediment into the other body of water
• Factors that affect the size of waves 


  Wind Strength

  The Fetch (distance the wave has travelled)

  The length of time the wind has been blowing
• Discordant Coastline


  Has more than one type of rock exposed

  Runs perpendicular to the sea
• Concordant Coastline 


  Has one type of rock exposed

  Runs parallel to the coast