Coasts

• Depositional landforms


  Coastal landforms that occur where there is a net gain of sand/shingle
• Constructive waves

  • Don't have enough energy to transport sediment, deposit it instead
• Deposition


  • Also caused by rapid coastal erosion providing abundant supply of material
• 20% of coastlines are depositional
• 70% of coastlines experience net erosion
• Beach inputs

  • Longshore drift
  • Swash
  • Beach nourishment
  • Cliff/dune erosion
• Beach outputs

  • Longshore drift
  • Backwash
  • Offshore wind transport
  • Storm events (quarrying)
  • Fluvial sediment
• Beach


  Depositional landform extending from highest high tide to lowest low tide, found where land meets sea, composed mainly of sand/shingle
• Beach accretion


  Caused by constructive waves
• Beach excavation

  Caused by destructive waves, removes sediment exposing wave-cut platforms
• Ridges and runnels

  • Series of ridges and troughs parallel to coast near low water mark, ridges formed by deposition during backwash, runnels formed when water retreats
• Ripples


  • Small, elongated ridges formed on beach by waves/current flows across loose sand, dragged along bottom, piling up
• Cusps

  • Semi-circular shaped depressions, coarser material around edge, fine material in middle, formed by collection of waves reaching same point and backwash scouring out fine material in centre
• Berms


  • Small ridges that form near high tide mark, deposited by swash of constructive waves, series indicates weekly high tide cycle
• Storm beach


  • Ridge near back of beach composed of larger sediment, deposited by destructive waves during storms
• Types of beach

  • Swash aligned
  • Drift aligned
• Chesil Beach, Dorset


  • High-energy, 29km long shingle ridge, reshaped by longshore drift, important sediment store
• Hanko, Finland

  • Low energy, constructive waves cause deposition of fine materials, large sandy beaches
• Beach profiles

  • Show cross-sectional shape of beach, material varies in size/regularity, larger at top, more rounded at bottom, seasonal changes in wave type create summer/winter profiles
• Spits

  • Long, narrow beach of sand/shingle with one end attached to shore and other extending into sea/estuary, formed by longshore drift
• Tombolo

  • Spit that connects mainland to offshore island
• Bars


  • Spits that develop across a bay, no strong water flow from landward side allowing sediment to be transported across headlands
• Barrier islands/beaches

  • Long, sandy stretch of land parallel to mainland, protecting it from destructive waves, with a protected lagoon or bay behind
• Sand dunes


  • Ridges/hills of accumulated sand, at top of beach above maximum wave reach, dynamic with inputs and outputs
• Inputs required for sand dunes to form

  • Large supply of sand
  • Large tidal range
  • Strong offshore winds
  • Obstacle to trap sand
  • Vegetation to stabilise sand
• Types of sand dunes

  • Embryo dunes
  • Fore dunes
  • Yellow dunes
  • Grey dunes
• Dune slack


  • Found between mature dunes, where water table reaches surface causing waterlogging and surface water
• Psammosere

  Ecological succession that began life on newly exposed coastal sand, most commonly sand dune systems
• Climax vegetation

  Dominant mix of vegetation species that characterise an environment, given time for colonisation to occur and reach stability
• Plant succession


  Directional change in the types of plant species that occupy a given area through time, involving colonization, establishment, and extinction