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Experiments by Invited Researchers

 

Large scale experiments of overtopped wave loads on storm walls

Project acronym: H+-Deltares-03-DF-Kortenhaus
Name of Group Leader: Andreas Kortenhaus
User-Project Title: Large scale experiments of overtopped wave loads on storm walls
Facility: Delta Flume
Publications: MSc_Thesis_Krasimir_Marinov---TU-Delft.pdf
Master-Thesis-Hirt-(2017)---Analysis-of-wave-overtopping-impacts-on-storm-walls_version20171206.pdf
Waves-on-walls---SCACR2017.pdf
CoastDoc18_Hirt_Analysis-of-wave-overtopping-impacts-on-storm-walls.pdf

WaLoWa stands for Wave Loads on Walls and is a Hydralab+ project funded by the European Union. Ghent University (Belgium), TU Delft (The Netherlands), RWTH Aachen (Germany), Politechnico Bari and University of Florence (Italy) and Flanders Hydraulics Research (Belgium) are jointly working on the WaLoWa project. The user team leader is Ghent University. The WaLoWa project is hosted by Deltares and the Delta Flume facility.

When storm walls and buildings are located on top of a dike or promenade, overtopping waves can induce large forces on these structures as has e.g. been observed at the Belgian coast which has a specifically shallow foreshore. Especially during storm season and in times of sea level rise these loads can be highly destructive. It is therefore the key objective of WaLoWa to study overtopped wave loads on structures situated on top of a dike and in shallow foreshore conditions. More detailed objectives comprise:

  1. To empirically relate the impact loads to structural parameters (e.g. dike slope, promenade width) and hydrodynamic parameters (e.g. water level, wave parameters, overtopping flow thicknesses and velocities) and to eventually develop design guidance for storm walls and buildings on top of a dike;
  2. To investigate scale effects of wave impacts by comparing the results obtained in the Delta Flume to small scale tests conducted for a similar geometry;
  3. To study the sandy foreshore evolution under wave attack and further calibrate the numerical model XBeach;
  4. To further calibrate numerical models such as the SWASH model (for the wave parameters on the shallow foreshore) and SPH model (for high resolution impact modeling);
  5. To investigate the instantaneous overtopping by means of overtopping flow thicknesses and velocities and to study the incoming and reflected bore characteristics on the promenade;
  6. To develop new measurement techniques, e.g. by using a laser scanner to survey the wave parameters at the dike toe, overtopping, overtopped flow formation and run-up on the wall simultaneously.

Large scale experiments in the Delta Flume facility at Deltares in Delft (The Netherlands) are deployed to study the overtopping flow and impact processes for the above described geometry. A scale model of a typical Belgian coastal profile (1/4.3 scale) is constructed within the Delta Flume. It is comprised of a foreshore built from 1000m³ of compacted sand. The foreshore has an initial slope of 1/10 and is followed by the main foreshore body with a slope of 1/35. Along the foreshore the wave parameters are measured until the dike toe location. The dike is constructed from concrete with a slope of 1/2. Attached is a concrete promenade of 2.3m length. Overtopping bore thicknesses and velocities are measured on the promenade. At the end of the promenade, a steel wall is constructed to block the overtopping flow and to measure the bore impact loads, run-up and the aeration of the flow at the wall. Waves representing a storm with a 1000 year return period and an additional water level to account for sea level rise result in the tested so-called ‘superstorm’ conditions.

The experiments will be conducted in March 2017 and the progress of the work can be followed on twitter @WaLoWa_tests. 

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