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DSD-INT 2018 The Ems estuary - long term morphological modelling as calibration exercise - Schrijvershof

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Presentation by Reinier Schrijvershof, Deltares, The Netherlands, at the Delft3D - User Days (Day 3: Sediment transport and morphology), during Delft Software Days - Edition 2018. Wednesday, 14 November 2018, Delft.

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DSD-INT 2018 The Ems estuary - long term morphological modelling as calibration exercise - Schrijvershof

  1. 1. The Ems estuary Long-term morphological modelling as calibration exercise Delft3D User Days 2018: Sediment Transport and Morphology Reinier Schrijvershof Bas van Maren Julia Vroom Mick van der Wegen
  2. 2. Introduction Simulated time Modelperformance 14 November 2018
  3. 3. Introduction Simulated time Modelperformance Shortterm(<1yr) 14 November 2018
  4. 4. Introduction Simulated time Modelperformance Shortterm(<1yr) Medium term (decades) 14 November 2018
  5. 5. Introduction Simulated time Modelperformance Shortterm(<1yr) Medium term (decades) Long term (centuries) Interventions 14 November 2018
  6. 6. Scope of work Calibration: Long term morphological development (Hindcast long term)Validation: Medium Term morphological development (Hindcast ~50 – 100 yrs) Forecast (scenarios ~50 – 100 yrs) 3D mud model Evaluation of measures Delft3D-FLOW Delft3D-WAVE SWAN engine Delft3D-WAQ DELWAQ engine
  7. 7. Scope of work 14 November 2018 Validation: Medium Term morphological development (Hindcast ~50 – 100 yrs) Forecast (scenarios ~50 – 100 yrs) 3D mud model Evaluation of measures Calibration: Long term morphological development (Hindcast long term) Aim of modelling exercise: 1. Derive settings for a long term morphologic forecast model 2. Understand the long term morphodynamics
  8. 8. The Ems-Dollard estuary
  9. 9. The Ems-Dollard estuary • The outer estuary Sandy shoals and deep channels
  10. 10. The Ems-Dollard estuary • The outer estuary Sandy shoals and deep channels • The middle estuary Former two channel system that degenerated into a single deep channel
  11. 11. The Ems-Dollard estuary • The outer estuary Sandy shoals and deep channels • The middle estuary Former two channel system that degenerated into a single deep channel • The Dollard Bay A vast expense of mudflats
  12. 12. The Ems-Dollard estuary • The outer estuary Sandy shoals and deep channels • The middle estuary Former two channel system that degenerated into a single deep channel • The Dollard Bay A vast expense of mudflats • The upper estuary (Ems river)
  13. 13. The Ems-Dollard estuary
  14. 14. 1250 AD 1550 AD present The Ems-Dollard estuary • 1250: funnel-shaped, relatively narrow estuary flanked by reclaimed land Vos (2015)
  15. 15. 1250 AD 1550 AD present The Ems-Dollard estuary • 1250: funnel-shaped, relatively narrow estuary flanked by reclaimed land • 1550: largest extent of the Ems estuary Vos (2015)
  16. 16. 1250 AD 1550 AD present The Ems-Dollard estuary • 1250: funnel-shaped, relatively narrow estuary flanked by reclaimed land • 1550: largest extent of the Ems estuary • 2000: most of the Dollard reclaimed Vos (2015)
  17. 17. The Ems-Dollard estuary 1812 1859 1911 1949 Oostereems Bocht Van Watum Westereems OFG What mechanisms triggered these changes in channel morphology? Gerritsen (1952) Flood Ebb
  18. 18. Model set-up • 2Dh model • Astronomical boundary conditions (nested) • Neumann type of b.c. • Constant river discharge • Sand and mud Neumann (nested) Neumann (nested) Neumann 𝑑ξ 𝑑𝑥 = 0 Neumann 𝑑ξ 𝑑𝑥 = 0 Qconstant Modified after Vos (2015)
  19. 19. Model set-up 11 december 2018
  20. 20. Calibration 1. Initial bathymetry (zb = NAP -4 m) 2. Necessity for added wave stresses (Hs,const = 0.2 m) 3. Transverse slope transport (αBn = 25) 4. Roughness and roughness predictors (0,022 s/m1/3) 5. Morphological acceleration factor (MorFac = 400) and total simulation time (800 yrs) 14 November 2018
  21. 21. 11 december 2018
  22. 22. 11 december 2018
  23. 23. 11 december 2018
  24. 24. Calibration 11 december 2018 Pierik, Busschers, and Kleinhans (2018) Erosion resistant layers Depth
  25. 25. Calibration 11 december 2018 Pierik, Busschers, and Kleinhans (2018) Pierik, Busschers, and Kleinhans (2018)
  26. 26. Results Uniform hard layer Palaeo mapped layer Depth top hard layer
  27. 27. Results
  28. 28. Results 14 November 2018
  29. 29. Results 11 december 2018 ‘present’ shoreline‘1550’ shoreline
  30. 30. Results 11 december 2018
  31. 31. Results 11 december 2018
  32. 32. Results 11 december 2018
  33. 33. Conclusions 1. The morphological development in the Ems estuary is altered by the presence of erosion resistant layers in the subsurface 2. Land reclamations contributed to the transformation from a two to one-channel system 3. Long term morphological modelling is a valuable way to calibrate (some) model settings and gain knowledge on estuarine morphodynamics Relative contribution? 14 November 2018
  34. 34. 11 december 2018 Questions?

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