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DSD-INT 2018 Barrier island breaching during Sandy and Matthew - Quataert

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Presentation by Ellen Quataert, Deltares, at the XBeach User Day 2018, during Delft Software Days - Edition 2018. Thursday, 15 November 2018, Delft.

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DSD-INT 2018 Barrier island breaching during Sandy and Matthew - Quataert

  1. 1. 15 November 2018 Barrier island breaching during hurricane Sandy and Matthew Ellen Quataert Marlies van der Lugt Johan Reyns Maarten van Ormondt Ap van Dongeren
  2. 2. IFMSIP IFMSIP: Increasing the Fidelity of Morphological Storm Impact Predictions • Modelling of hurricane impact on U.S. barrier island morphology • Improve accuracy of event-driven morphological predictions by • constraining free parameter space • identifying key processes • assessing sensitivity to variations in input • Collaboration with partners (USGS, U/Del, NRL), through the Office of Naval Research (ONR) 15 November 2018
  3. 3. 15 November 2018 Case studies 17 december 2018 Santa Rosa FL Bay Head, NJ Fire Island NY Wilderness Breach, NY Matanzas, FL Sandy Irene Matthew Ivan Ike Bolivar Peninsula, TX Monterey Bay, CA
  4. 4. 15 November 2018 Case studies 17 december 2018 Santa Rosa FL Bay Head, NJ Fire Island NY Wilderness Breach, NY Matanzas, FL Sandy Matthew Ivan Ike Bolivar Peninsula, TX Monterey Bay, CA
  5. 5. Case study 1: Bay Head, NJ 15 November 2018
  6. 6. Bay Head, NJ 15 November 2018 09/2012: pre Sandy
  7. 7. Bay Head, NJ 15 November 2018 09/2012: pre Sandy 11/2012: post Sandy rock seawall
  8. 8. Sandy hydrodynamics 15 November 2018 D-Flow FM / SWAN model (wind fields Navy) Bay Head
  9. 9. Sandy hydrodynamics 15 November 2018 D-Flow FM / SWAN model (wind fields Navy) Bay Head
  10. 10. XBeach model input 15 November 2018 • Pre-Sandy LIDAR survey by USGS • includes vegetation
  11. 11. XBeach model input 15 November 2018 • Pre-Sandy LIDAR survey by USGS • includes vegetation • Model by Smallegan et al. (2016) • Building locations determined using Google Earth imagery • Non-erodible buildings and buried seawall • XBeach settings of Wilderness breach case
  12. 12. Model – data comparison 15 November 2018 PRE POST DIFF OBSERVED Post-lidar survey on 5 November 2012 (landfall Sandy 29 October 2012)
  13. 13. Model – data comparison 15 November 2018 PRE POST DIFF OBSERVED MODELLED
  14. 14. Model – data comparison 15 November 2018 PRE POST DIFF OBSERVED MODELLED DIFFERENCE
  15. 15. Model – data comparison 15 November 2018
  16. 16. Model – data comparison 15 November 2018 • XBeach underestimates erosion behind the seawall • Good model performance seaward of the seawall
  17. 17. Case study 2: Matanzas breach, FL 15 November 2018
  18. 18. Breach after hurricane Matthew 15 November 2018 02/17/2016: pre Matthew marsh Complex barrier island case with: • Waterway • Marsh • Road • Houses on the dune • Different types of vegetation
  19. 19. Breach after hurricane Matthew 15 November 2018 02/17/2016: pre Matthew 11/19/2016: post Matthew Breach 120m wide marsh
  20. 20. LIDAR survey by USGS 15 November 2018 Pre Matthew Post Matthew
  21. 21. LIDAR survey by USGS 15 November 2018 • Low dune height Pre Matthew Post Matthew
  22. 22. LIDAR survey by USGS 15 November 2018 • Low dune height • No bars in pre-Matthew observations Pre Matthew Post Matthew
  23. 23. LIDAR survey by USGS 15 November 2018 • Low dune height • No bars in pre-Matthew observations • No houses in topography Pre Matthew Post Matthew
  24. 24. LIDAR survey by USGS 15 November 2018 • Low dune height • No bars in pre-Matthew observations • No houses in topography • Post-lidar 2 months after Matthew Pre Matthew Post Matthew
  25. 25. Matthew hydrodynamics 15 November 2018 D-Flow FM / SWAN model Matanzas breach
  26. 26. Matthew hydrodynamics 15 November 2018 Matanzas breach D-Flow FM / SWAN model
  27. 27. XBeach model input 15 November 2018 marsh • Pre-Matthew LIDAR survey by USGS • XBeach settings of Wilderness breach case
  28. 28. XBeach model input 15 November 2018 marsh • Pre-Matthew LIDAR survey by USGS • XBeach settings of Wilderness breach case used • Bed friction of n = 0,04 for bed > 0 m
  29. 29. Model – data comparison 15 November 2018 Observed Modelled • XBeach predicts breaches, but at a different location
  30. 30. Effect of water levels on dune crest height 15 November 2018
  31. 31. Roughness based on land cover classification Sand, water 15 November 2018 Structure, roads, woody vegetation Wetland vegetation Dune grass roughness map based on land cover classification uniform roughness for bed > 0 m
  32. 32. Roughness based on land cover classification Sand, water Structure, roads, woody vegetation Wetland vegetation Dune grass roughness map based on land cover classification uniform roughness for bed > 0 m 15 November 2018
  33. 33. Effect of varying roughness 15 November 2018 Observed Modeled with roughness map
  34. 34. Effect of varying roughness 15 November 2018 Observed Modeled with roughness map
  35. 35. Effect of water levels on dune crest height 15 November 2018
  36. 36. Conclusions • Two complex barrier island cases with houses, structures and vegetation, showing a strong morphological response to hurricane Sandy and Matthew • XBeach gives a good prediction of dune erosion and breaching using similar model settings • But model results sensitive to structures, (spatially-varying) bed friction and pre-storm topography 15 November 2018
  37. 37. Conclusions • Two complex barrier island cases with houses, structures and vegetation, showing a strong morphological response to hurricane Sandy and Matthew • XBeach gives a good prediction of dune erosion and breaching using similar model settings • But model results sensitive to structures, (spatially-varying) bed friction and pre-storm topography Next steps • What is the sensitivity in XBeach outcome to given uncertainties in: • Model settings: facua, roughness maps • Boundary conditions: surge level • Pre-storm bathymetry and topography • Our goal: a XBeach model to simulate morphological response of complex U.S. barrier islands to hurricanes 15 November 2018

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