Effect of Different Sediment Mixtures on the Longterm morphological Modeling of Tidal Basins - PowerPoint PPT Presentation

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Effect of Different Sediment Mixtures on the Longterm morphological Modeling of Tidal Basins

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2000 Var. d50. 1930-2000. Next Steps. Add finer sand to the fractions ... Run 1930-2000 simulations with number of sediment fractions ... – PowerPoint PPT presentation

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Title: Effect of Different Sediment Mixtures on the Longterm morphological Modeling of Tidal Basins


1
Effect of Different Sediment Mixtures on the
Long-term morphological Modeling of Tidal Basins
NCK Days 2009 Texel
  • Ali Dastgheib, Dano Roelvink, Mick van der Wegen

2
Introduction (why?)
  • Recently the process-based morphological models
    are used more often in mid-term (decades) or
    long-term (centuries)
  • Very long-term Simulations, West Eschelt (Mick
    van der Wegen)
  • Texel inlet (Edwin Elias)
  • Marsdeip (Ali Dastgheib)
  • Willapa Bay (G. Lesser)
  • One of the main shortcomings of the results are
    unrealistic narrow and deep channels.

3
Morphological model mid/long-term
Morpholgical Tide Wave condition
Hydro- dynamics
Sediment Transport Relations Slope
effect Avalanche effect
RAM Correction factor Online
Morphological changes
Sediment / Transport
  • In most of the mid/long-term morphological
    simulation the sediment is schematized with one
    D50 over all the model

4
Research objectives
  • In this research our focus is on the use of
    different sediment fractions in order to model
    some of the neglected processes and show their
    effects on the long-term simulation of tidal
    basins (Wadden Sea is selected as the case study)
  • Further more we want to suggest a procedure to
    use the result of this research in practice

5
Available Data
  • Soil Sampling in the Dutch Wadden Sea
  • 1989 1997
  • Malvern laiser particle sizer
  • summerized in SedimentAtlas of Wadden Sea

6
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7
Available Data
8
Available Data
9
Sediment Size Schematization
10
Sediment Size Schematization
  • 6 Sediment Fractions based on the sieve test
  • Min of 75µm to max of 2.36 mm
  • Min diameter, Max diameter (425 600 µm)
  • loguniform distribution
  • No cohesive Sediment
  • No Mud

11
Sediment Size Schematization
12
Case Wadden Sea
M-Direction70 N-Direction127 Nr of Grid
Cells6876
Vl
Ei
Ma
13
Model Setup
  • Forcing
  • M2,M4,M6
  • O1,K1 (C1)
  • Bed Slope Effect
  • Dry Cell Erosion
  • Mor. Fac 300
  • Mor.Time 500 yrs
  • 5 Simulations

D - 4.54
14
Hypsometry
15
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16
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17
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18
What is the use of it?
  • Maybe we can have an intelligent guess for the
    initial condition in real case morphological
    simulations.
  • Relate the d50 Variance of Velocity
  • Hydrodynamic simulations for 5 tidal cycles using
    the resulting bathymetries

19
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20
Real Case Wadden Sea 1930
M-Direction140 N-Direction254 Nr of Grid
Cells6876
Vl
Ei
Ma
21
Available Bathymetry data
  • 1926 2007
  • UCIT Data
  • MATALB Routine, Make a bathymetry for desired
    year
  • Linear interpolation between available data
  • If the target year is earlier than the first
    observation or later the last one within the 5
    years different, the available data was used
  • Projected on the Computational mesh

22
Model Setup
  • Forcing
  • M2,M4,M6
  • Bed Slope Effect
  • Dry Cell Erosion
  • Mor. Fac 75
  • Mor. Time 75 yrs
  • Initial bathymetry
  • 1930
  • One Fraction with spatially varying d50

23
1930-2000
2000 Var. d50
2000 One d50
2000
1930
24
1930-2000
25
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26
Next Steps
  • Add finer sand to the fractions
  • Compare the Basin Characteristics
  • Compare the Skill Score of the Models
  • Run 1930-2000 simulations with number of sediment
    fractions
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