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TYPES OF TRANSPORT

TYPES OF TRANSPORT. Bedload - supported by inter-granular collisions. arth.geol.ksu.edu. University of Aberdeen. TYPES OF TRANSPORT. Suspended load - supported by turbulent fluctuations. Univ twente. LITTORAL TRANSPORT. Transport along the coast.

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TYPES OF TRANSPORT

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  1. TYPES OF TRANSPORT Bedload- supported by inter-granular collisions arth.geol.ksu.edu University of Aberdeen

  2. TYPES OF TRANSPORT Suspended load- supported by turbulent fluctuations Univ twente

  3. LITTORAL TRANSPORT Transport along the coast. Can occur in both directions depending on wave climate NET: sum of positive and negative drifts GROSS: sum of positive and negative drift magnitudes. How to measure??? No “miracle” longshore sediment transport meter exists!

  4. FOBS LITTORAL TRANSPORT MEASURING TECHNIQUES 1) Current meters and optical or acoustic basckscatter sensors. Product of 2 is estimate of instantaneous transport. Difficulty, hard to image both signals over water column depth. Bedload problematic, bubbles deteriorate signal.

  5. LITTORAL TRANSPORT MEASURING TECHNIQUES 2) Streamer traps or other trapping mechanism Integrated transport only Can get time dependent info LSTF at ERDC Sediment traps Komar, 1998

  6. LITTORAL TRANSPORT MEASURING TECHNIQUES 3) Amount of required dredge material Dredge hole http://bio.sbcc.net/tur/img/aircc.jpg

  7. LITTORAL TRANSPORT MEASURING TECHNIQUES 4) Tracer study: Use dyed or irradiated grains. Geiger counter

  8. LITTORAL TRANSPORT MEASURING TECHNIQUES 5) Continuity equation along with measured bathymetry differences

  9. LITTORAL TRANSPORT CALCULATIONS All essentially reduce to a form of the wave power With units of volume per time C is NOT dimensionless Better: With units of immersed weight per time K IS dimensionless

  10. LITTORAL TRANSPORT CALCULATIONS The coefficient, K, is normally given as about 0.77 if Hrms is used. Note the scatter and log-log scale Slope gives K

  11. LITTORAL TRANSPORT APPLICATIONS Preceding based on breaker information which we rarely have. If we make some assumptions like straight and parallel contours, negligble energy losses from offshore and small incidence angles at breaking, we can use Energy conservation, Snell’s Law and shoaling to relate equation to offshore parameters only. S is ration of sediment to water density. If we assume breaker angle small than the cosine term in the denominator goes to one. Still looks ugly

  12. LITTORAL TRANSPORT APPLICATIONS Littoral Drift Rose (LDR) can be used to shore variations in transport due to variations in shoreline orientation. Drift roses are constructed using available data and longshore sediment transport equation. D&D

  13. LITTORAL TRANSPORT APPLICATIONS LDR predicts accentuation of erosive feature LDR predicts smoothing of erosive feature

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