DSD-INT 2018 From milliseconds to centuries: long-term coastal morphology modelled with a new wave orbital motion parameterization - Boechat Albernaz
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This document compares two methods of parameterizing wave orbital motion - Isobe & Horikawa (IH) and Ruessink et al. (RUE) - in long-term coastal morphology models spanning timescales from milliseconds to centuries. The IH method leads to overestimated sediment transport, excessive morphological diffusion, and a lack of channels and erosion of flats in model results. The RUE method produces hydrodynamics and sediment transport more consistent with field measurements, resulting in modelled morphology that more closely matches natural coastal systems with better-developed channels and less diffusive features. Overall, the RUE parameterization provides substantial improvements over IH for modelling long-term coastal evolution.
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DSD-INT 2018 From milliseconds to centuries: long-term coastal morphology modelled with a new wave orbital motion parameterization - Boechat Albernaz
- 1. Faculty of Geosciences River and delta morphodynamics From milliseconds to centuries: long-term coastal morphology modelled with a new wave orbital motion parameterization Márcio Boechat Albernaz PhD Candidate – m.boechatalbernaz@uu.nl Gerben Ruessink Dirk-Jan Walstra Pieter Koen Tonnon Bert Jagers Maarten Kleinhans
- 3. Introduction 3 Long-term morphology Tides + Waves Why? Inlet enlargement Diffusive morphology Lack of channels Erosion of flats
- 4. Wave shape Not fully resolved in morphodynamic models Parameterized 4
- 5. Wave shape Parameterizations: Isobe & Horikawa 1982 (IH) – in Delft3D ■ Derived from experiments ■ 3rd Cnoidal + 5th Stokes Ruessink et al 2012 (RUE) ■ Derived from field measurements ■ Ursell number 5
- 6. Wave shape Intra wave orbital velocities: “Offshore” IH -> Skewed?! RUE -> Sin 6
- 7. Wave shape Intra wave orbital velocities: Shoaling zone IH -> More Skewed RUE -> Skewed “Offshore” IH -> Skewed RUE -> Sin 7
- 8. Wave shape Intra wave orbital velocities: Surf zone IH -> Skewed RUE -> As/Sk Shoaling IH -> Skewed RUE -> Skewed “Offshore” IH -> Skewed RUE -> Sin 8
- 9. Sediment transport predictor Van Rijn 2004/2007 ■ Bed load ■ Suspended load Critical Shields + Non-linear term Non-linear Skewed based transport Uon & Uoff 9
- 10. Model implementation Implemented RUE into Delft3D source code IH is the default parameterization VR04 sediment transport (w/ intra wave) 10 2DH model 50 – 12 m resolution M2 tides SWAN wave model 200-250 µm sand 10-100 yrs 10-50 morfac
- 11. Cross-shore Non-Linearities Swell wave: Hs=1m Tp=8s skewness Sk/As As/Sk skewness sinusoidal No asym 11
- 12. Model Forcing Wave reduction Wave reduction - energy 13 cases ~25 yrs measurements IJmuiden munitiestortplaats <http://live.waterbase.nl> 12
- 13. Cross-shore Morphology Default sediment transport values 10 yrs Beach Envelop Closure depth “Scour” Shoreline 13
- 14. Bed U Sus U Total ON OFF Cross-shore Sed. Transport Yearly net transport Default: ■ HIGH bed load [IH] ■ on/off unbalance Calibration: ■ equal bed / sus ■ ON = OFF [total=0] 14 4.6 x bed load 15% 72% 15% 20% ON OFF
- 16. Alongshore Sediment Transport 16/19 N S N S Bed V Sus V Total 15% 72% 15% 20% Yearly net transport Default: ■ IH higher than RUE (Xshore) Calibration: ■ RUE higher than IH!
- 17. NOT Alongshore Uniform Coastal Hump ~3.7Mm³ 17/19 IH RUE
- 18. Alongshore Sediment Transport Volume diffusion IH slower diffusion – littoral drift 18/19 IH RUE
- 19. Complex [shallow] morphology 19 Can we get it right? Or closer to
- 20. Tidal Basin Morphology Wave climate – 100 yrs Xshore Calibrated values IH - 20% RUE - 80% 20
- 21. 21 Tidal Basin Morphology “Same” (XShore) transport values – large differences!
- 22. Tidal Basin Morphology Inlet, Channels and shoals Ameland
- 23. Tidal Basin Morphology Basin IH overshallowing & diffusion Inlet expansion Channel infilling & shallowing
- 24. Tidal Basin Morphology Delta RUE smaller delta [eroded barrier?] IH diffusive morphology Asymmetry/Skewness Skewness
- 25. 25 Conclusions Tidal IH – 20% RUE - 80% Inlet enlargement Diffusive morphology Lack of channels Erosion of flats
- 26. Conclusions “Same” transport -> [very] different [long-term] morphology Isobe Horikawa (skewness only) Higher XShore sediment transport – strong unbalance of transport modes Over-calibration of transport magnitude (is it correct then?) Decoupling of Xshore & Alongshore processes [Shoreline & Littoral drift] Excessive morphological diffusion Ruessink (skewness + asymmetry): No need to over-calibrate transport due to correct hydrodynamic processes Incision & Diffusion more balanced with nature and tidal (only) models Overall morphology closer to observed in nature Márcio Boechat Albernaz PhD Candidate – m.boechatalbernaz@uu.nl 26