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Beach-dune interaction for dynamic coastal management

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Keynote Dynamic Dunes Congress 2015:
Gerben Ruessink - Beach-dune interaction for dynamic coastal management

Published in: Environment
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Beach-dune interaction for dynamic coastal management

  1. 1. Faculty of Geosciences Faculty of Geosciences Beach-dune interaction for dynamic coastal management Gerben Ruessink
  2. 2. Faculty of Geosciences Beach-dune interaction Urgency: • nature restoration • long-term coastal safety No sand sharing: (1) loss in geomorphological dynamics (2) loss in biodiversity (3) no vertical growth with sea-level rise Dune erosion Dune growth
  3. 3. Faculty of Geosciences Building with Nature: Sand Engine 5 July 2011 10 January 2012 1 October 2013 1 oktober 20134 May 2015
  4. 4. Faculty of Geosciences Building with Nature: Sand Engine Beach-dune interaction: • Short gradients (new embryo dunes) • Foredune growth ~ 15 m3/m/year • No dune erosion
  5. 5. Faculty of Geosciences Building for Nature: NWNKern
  6. 6. Faculty of Geosciences Building for Nature: NWNKern Trenches: V- to U-shape Construction After 2 years Foredune scarping Sedimentation lobes
  7. 7. Faculty of Geosciences Combination: HPZ
  8. 8. Faculty of Geosciences Questions • How much sand is actually blown toward the dunes? • Which factors affect this amount? • What to expect from dune remobilization? • Are present-day large-scale measures effective? • Can nourishments and dune remobilization be combined? • …
  9. 9. Faculty of Geosciences Needs • Experiments: Learning by doing • Long-term (years) monitoring with high resolution (seasons) • Close co-operation between stakeholders and scientists • Models with different complexity • …
  10. 10. Faculty of Geosciences Beach-dune interaction: models Keysers et al. (2014) Plos ONE Poseidon Aeolus
  11. 11. Faculty of Geosciences My projectBeach-dune interaction: models Need Accurate predictive model of aeolian sand supply Challenges Supply limitation 1. How wet? 2. When? 3. How much? 4. Upscaling
  12. 12. Faculty of Geosciences Timing of aeolian events Potential transport • Events (4 hrs > 8 m/s) • Hsu (1974) Observed transport • Sand-strip activity
  13. 13. Faculty of Geosciences Timing of aeolian events Mismatch between potential and actual events: • Moderate wind speeds: considerable aeolian activity • Large speeds are large: no aeolian activity
  14. 14. Faculty of Geosciences Considerable aeolian activity under moderate, shore-oblique/parallel winds Timing of aeolian events
  15. 15. Faculty of Geosciences Timing of aeolian events No aeolian activity under strong shore-normal / oblique winds because of surge
  16. 16. Faculty of Geosciences Summary • From preventing dune-erosion to beach-dune interaction • Building with and for Nature • Practice-inspired questions and scientific ideas • Pilot experiments: ‘Learning by doing’ with long-term monitoring to eventually predictively understand Only then ready for the challenges of the decades to come
  17. 17. Faculty of Geosciences
  18. 18. Faculty of Geosciences Surface moisture content saturated Reflection (dB) Moisturecontent(%) dry
  19. 19. Faculty of Geosciences Surface moisture content
  20. 20. Faculty of Geosciences Mismatch between potential and actual events: • Moderate wind speeds: considerable aeolian activity • Large speeds are large: no aeolian activity Timing of aeolian events
  21. 21. Faculty of Geosciences Transport magnitude
  22. 22. Faculty of Geosciences Results (Xaver) -80 -70 -60 -50 -40 -30 0 5 10 15 20Elevation(mMSL) -80 -70 -60 -50 -40 -30 0 5 10 15 20 Elevation(mMSL) Distance (m) before after I. Destruction of new foredune and embryo dunes -80 -70 -60 -50 -40 -30 0 5 10 Elevatio -80 -70 -60 -50 -40 -30 0 5 10 15 20Elevation(mMSL) Distance (m) -80 -70 -60 -50 -40 -30 0 5 10 15 20 Elevation(mMSL) -80 -70 -60 -50 -40 -30 0 5 10 15 20 Elevation(mMSL) Distance (m) II. Failure of dune front with successive rotational slides before after
  23. 23. Faculty of Geosciences -80 -70 -60 -50 -40 -30 0 5 10 15 20 Elevation(mMSL) -80 -70 -60 -50 -40 -30 0 5 10 15 20 Elevation(mMSL) Distance (m) before after storm recovery Results (post-Xaver)

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