University of Twente Student Theses


The effects of storm surges on dune systems near inlets : A case-study for the Marsdiep inlet near Texel

Broek, Stan van den (2017) The effects of storm surges on dune systems near inlets : A case-study for the Marsdiep inlet near Texel.

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Abstract:During storm surges, the water level and wave height increase which results in erosion of the dunes. Extreme storm surges are capable of eroding or even breaching dunes. A lot of research has been done on the effects of storms on straight (uniform) coasts. Still, there is a gap in the accurate prediction of storm-induced coastal change on coastal dune systems near tidal inlets. The goal of this research is to understand the behaviour of storm surge processes on a coastal dune system near a tidal inlet system. Thus, we aim at understanding how storm characteristics influence on coastal dune erosion and sedimentation on systems near tidal inlets. XBeach, a numerical model which is developed for simulating extreme storm surges in complex situations like a tidal inlet system, is used to make a simulation of various storm surges in the Marsdiep inlet (NL). On the north side of the inlet, a large sandflat (‘the Hors’) is located. The choice to use this particular inlet is made because of the availability of the necessary data which was essential to run and qualitatively validate the model. Results show that most wave energy is dissipated before reaching the dunes, thus leading to a decrease in the radiation stress. The reduction results in an increase of the water level on the west side of the sandflat. The water level gradient, created by the wave-set up, results in a constant flow across the Hors from west to east. Erosion, caused by the dissipated energy, is observed on the west coastline of the sandflat. The eroded material is partly transported on top of the Hors, where it settles as the water depth increases and the flow velocity decreases. The rest of the eroded material is transported southwards where it settles behind the southern tip of the sandflat, where the current magnitude decreases significantly. Water level gradient between both sides of the inlet had significant influence in the current magnitude and erosion values in/near the channel of the inlet. Higher water levels had almost no effect on both the hydrodynamic as morphodynamical processes in the inlet as they were found to be dominated by (indirectly) wave breaking on the west side of the sand flat. These results could be used in management strategies to create a more stable or even expanding barrier island. could be used as interpretation of the hydrodynamical and morphodynamical behaviour in tidal inlets during storm surges. However, as all tidal inlets have different topographic and climate characteristics, more research is necessary to test the influence of these variables on the hydrodynamic (and morphodynamical) behaviour on the dune systems.
Item Type:Essay (Master)
Faculty:ET: Engineering Technology
Subject:56 civil engineering
Programme:Civil Engineering and Management MSc (60026)
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