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Dune erosion during storm surges

Jaap van Thiel de Vries. Dune erosion during storm surges. Picture: Beach and dunes near Westenshouwen. Dune erosion. Post-surge beach width. Post-surge dune foot. Maximum storm surge level. Pre-surge dune foot. Mean sea level. Pre-surge beach width. Dune erosion during storm surges.

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Dune erosion during storm surges

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  1. Jaap van Thiel de Vries Dune erosion during storm surges Picture: Beach and dunes near Westenshouwen

  2. Dune erosion Post-surge beach width Post-surge dune foot Maximum storm surge level Pre-surge dune foot Mean sea level Pre-surge beach width Dune erosion during storm surges

  3. Societal importance • Dutch safety policy against flooding: • “Dijkringen” • Weakest link in a “dijkring” determines safety against flooding • Strength primary water defenses against normative conditions is assessed every five years. • Strength dunes is assessed with empirical guideline elaborated from large scale dune erosion experiments Dune erosion during storm surges

  4. Societal importance Scheveningen Hondsbosche en Pettemer sea defense Head of Noord-Holland Head of Walcheren Dune erosion during storm surges

  5. Thesis outline Objective: Improve our physical understanding of dune erosion in order to develop a more generic dune erosion model. Thesis outline: • Large scale dune erosion tests in the Deltaflume • Interaction of dune and swash • New approach in modeling near dune hydrodynamics • New approach in modeling near dune sediment concentrations • Coupling of new physical insights in a 2DH morphodynamic model Dune erosion during storm surges

  6. Deltaflume experiment Dimensions: 220m x 5m x 7m Depth scale = 6 Irregular waves; Hm0=1.5m Dune erosion during storm surges

  7. Deltaflumemeasurements FLUME WALL In-situ MOBILE FRAME Stereo Video STEREO VIDEO Dune erosion during storm surges

  8. Deltaflumeresults Pressure sensors on flume wall: Suction tubes on shallow water frame: Lange golven Korte (wind) golven duin golfschot Dune erosion during storm surges

  9. Deltaflumeresults Dune crest Shore line Reflected wave Incoming bore Dune erosion during storm surges

  10. Modeling near dune hydrodynamics The generation of long waves due to variations in the wind generated short waves Dune erosion during storm surges

  11. Modeling near dune hydrodynamics Dune erosion during storm surges

  12. Modeling near dune hydrodynamics Dune erosion during storm surges

  13. Near dune sediment concentrations Hypthesis: High near dune sediment concentrations are caused by wave breaking induced turbulence that is injected in the water column over a short time interval and reaches the bed as a pulse. Tbore Dune erosion during storm surges

  14. Near dune sediment concentrations Dune erosion during storm surges

  15. XBeach New physical insights are coupled in the morphodynamic model XBeach that: • Solves both short waves (energy balance) and long waves (Nonlinear Shallow Water Equations); • Includes a formulation that also relates the sediment concentration to the wave breaking induced turbulence pulses that potentially reach the bed; • Includes the longshore direction. Dune erosion during storm surges

  16. LEF Restaurant en Bar Doelenplein 2, Delft Google maps Dune erosion during storm surges

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