2B.5a

• what is sediment transport affected by?

  • angle of wave attack
  • longshore drift
  • rides and currents
• how is sediment transport influenced by the angle of wave attack?

  angle of wave attack affects the direction of longshore drift. when the angle is small (more perpendicular to the shore), longshore drift is weak as the waves will retreat back to the sea, but if the angle is large (more parallel to the shore), longshore drift is strong so it transports sediment a long distance along the shore
• what are tidal ranges?

  Difference between high tide and low tide.
• how do tides and currents influence sediment transportation?

  • tides affect the position at which waves break on the beach - at high tide they break higher up the shore
  • the higher the tidal range, the more powerful the currents will be so more sediment is transported
  • when seawater goes into estuaries or other narrow areas, the tidal currents are particularly powerful --> these currents can transport a lot of sediment
• what is the process that sediment is mostly transported along the coast?

  Longshore drift
• how does longshore drift transport sediment?

  • waves approach the beach at an angle determined by the direction of the prevailing wind
  • as waves break, the swash carries sediment up the beach
  • backwash carries sediment back down the beach at right angles to the shore
  • the process repeats, transporting sediment along the beach in a zig-zag movement
• what are the 4 transportation processes?

  • solution
  • suspension
  • saltation
  • traction
• solution?

  dissolved material is carried in the water as a solution
• suspension?

  very fine material such as clay particles is carried along in the water column
• saltation?

  larger particles such as pebbles bounce along the sea bed due to the force of the water
• traction?

  very large particles like boulders are pushed and rolled along the sea bed by the force of water
• why does deposition occur?

  waves lose energy so can no longer carry the sediment
• why do waves lose energy?

  • wind dropping, removing an energy source
  • resistance by an obstruction e.g. groyne or headland
  • dissipation of energy through refraction
  • friction from extended transport across shallow nearshore zone
• what are the 2 ways sediment is transported?

  gravity settling

  flocculation
• gravity settling?

  the energy of transporting water becomes too low to move sediment. large sediment is deposited first, followed by small sediment
• flocculation?

  small particles such as clay are suspended in the water, they then clump together through electrical or chemical attraction and become large enough to sink