ESPL lecture 2

  • Created by: imogen-0
  • Created on: 29-05-22 16:57
View mindmap
  • ESPL - Aeolian block lecture 2
    • coastal aeolian systems
      • dunes  microscale controls
        • –Wind regime –Grain size    –Beach width –Beach slope
        • Controls on q (sand transport) Controls between grains - largest 1m scale Can make predictions but they are often quite flawed due to the everchanging nature and complexity of the interactions
        • Sarre (1989) - Braunton Burrows, SW England
          • Transport prediction equation Driving force related to V*
          • based on sarre the actual and measured movement were compared
            • Highest predictions for winter Highest actual rates in summer (sand condition and moisture)
            • predictions almost always higher then the observed
            • important variables
              • •Beach watertable (groundwater) •Tidal effects •Fetch (length of beach wind sees) •Evaporation + precipitation •Grain size
              • 1.Changes in the water table 2.Rainfall intensity 3.Amount of precipitation 
                • 4.Temperatures These factors impact susceptibility to erosion – although the wind is higher in winter the other conditions impact how susceptible the sand is to transport ?
          • Empirical equation is very site specific i.e. can apply to Braunton Burrows only
            • Corrected q = better agreement between predicted and actual, but still a lot of variance
      • influence of beach width on sediment transport
        • 1)Together with wind direction, beach width determines sand source extent 
          • 2)Together with thickness of sediment above beach water table, it determines total volume of sand available
            • 3)Indirectly influences sediment transport through effect of beach form and slope
        • BEACH WIDTH Width and wind direction determine source of sand Source as an Area X Depth = volume available to move 
      • carrying capacity and transport
        • Once threshold is reached the speed reached has its own threshold of sand it is capable to moving It becomes a saturated flux
          • – it cannot pick up any more sand Faster speeds of winds have greater ability to transport sand
      • MACRO SCALE interactions
        • relate types of coastal dune systems to beach types, and long-term sediment budgets
          • beach type
            • 1.Dissipative beach: strong wave energy, but energy dissipated in surf zone, some distance from beach face Used and lost in surf zone – crashing waves Surf zone is a far distance away from the beach zone – there is little beach wave interaction 
              • finer as the limited energy on the beach leads to finer sediment settling 
                • After due initiation the dunes are likely to progress due to the stable nature of the beach
            • 2.Reflective beach: wave energy dissipated on the beach Smaller width of beach meaning there is more interaction of the waves with the beach 
              • the larger energy means that coarser sediment can be brought on shore further up the beach. 
                • Variability in shear stress, sediment texture, surface roughness from wave energy – less stable to less likely for the dunes to progress and become mature
    • beach system
        • BEACH
          • out put to frontal dune from beach = 1 landward aeolian transport
          • input to beach = alongshore sand supply
          • out put from beach = alongshore sand loss
          • input = onshore sand supply
          • output = offshore sand loss
        • out puts to beach from dune  = 1 wave erosion  2 seaward aeolian transport
          • out put to land = 1 inland aeolian transport
      • Inputs (***) Outputs (ASL) These processes and their balance lead to aggradation or degradation
      • On-shore inputs (OSS) marine inputs Off-shore outputs (OSL) marine outputs
      • Fluxes between landforms
      • Erosional (WE) from dune to beach Erosional/depositional (LAT) from beach to dunes Erosional (SAT) from dune to beach Erosional (IAT) from dunes in land
      • Mablethorpe Lincolnshire
        • Use of the processes and landforms Manipulation of processes to promote deposition or prevent erosion Flux 
          • sizes and interaction levels These change the form of the dune and beach
        • Range of interactions control form and change Can look at micro, meso and macro-scales


No comments have yet been made

Similar Geography resources:

See all Geography resources »See all ESPL resources »