2D OVERTOPPING AND IMPACT EXPERIMENTS IN SHALLOW FORESHORE CONDITIONS

Vincent Gruwez,Andreas Kortenhaus,Maximilian Streicher,Toon Verwaest,Dogan Kisacik,Corrado Altomare,Ine Vandebeek,Peter Troch,Tomohiro Suzuki

doi:10.9753/icce.v36.papers.67

Abstract

This paper introduces the 2D experiments conducted for the CREST project in the wave flume of Ghent University. The experiments focus on wave interactions with low-crested sea dikes fronted by a shallow foreshore and mildly to steeply sloping beaches, which is a very typical situation along the Belgian coast. Foreshore slopes of 1/20, 1/35, 1/50 and 1/80 were tested for a range of low to high energy wave conditions, a variation in wave steepness and two water levels. The main goal was to obtain a dataset in which the effects of the infragravity waves on the wave-structure interactions (i.e. wave overtopping and impact forces) can be studied. The tests included high spatial resolution surface elevation measurement tests, which is new for beaches including a dike in the inner surf zone. From the first results it became clear that the foreshore slope influences the wave transformation up to the dike toe. The influence is apparent comparing to existing (semi-) empirical models for prediction of the spectral wave period at the dike toe and wave overtopping at the dike crest. The high spatial resolution data show a steep increase in infragravity significant wave height in the very shallow area in front of the dike.

Highlights

Wave-interactions with sea dikes and storm walls at deep and intermediate water depths have already been extensively investigated (Van der Meer et al, 2016)
Thanks to the high spatial resolution measurements of the surface elevation along the complete foreshore, a detailed analysis is possible of the wave transformation up to the toe of the dike and of the effects the presence of the dike has on it
The cross-shore evolution of the short wave significant wave height Hm0,hf, the infragravity wave significant wave height Hm0,lf, the spectral wave period Tm-1,0 and the wave setup are presented in Fig. 5, for foreshore slope 1/50 and the highest tested water level

Summary

INTRODUCTION

Wave-interactions with sea dikes and storm walls (e.g. reflection, wave run-up, overtopping, forces, etc.) at deep and intermediate water depths have already been extensively investigated (Van der Meer et al, 2016). COASTAL ENGINEERING 2018 of the experiments presented, are summarized as follows: (1) providing data for the validation of the numerical models being developed within the CREST project, (2) investigate the effect of the foreshore slope on both the wave transformation up to the dike toe and (3) the wave-structure interactions (i.e. overtopping and forces). In test condition RS05, the significant wave height was lowered compared to RS01 to a value which is estimated to closely representing the real (in a 3D environment) long wave energy content at the toe of the dike This was done as a way to take into account the effect of directional spreading on the amount of wave energy transfer to the infragravity wave band over a very shallow foreshore in a 2D wave flume (Suzuki et al, 2014). In addition to the second order generated random waves, some tests were repeated on the 1/35 and 1/50 foreshore (scale 1:25) using first order wave generation (RF) to investigate the effect on the wave transformation and individual wave overtopping (see Table 1)

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RESULTS

Test ID ho

CONCLUSIONS AND FUTURE WORK