Reduction of Wave Overtopping and Force Impact at Harbor Quays Due to Very Oblique Waves

Sebastian Dan,Tim Spiesschaert,Toon Verwaest,Corrado Altomare,Tomohiro Suzuki

doi:10.3390/jmse8080598

Abstract

Physical model experiments were conducted in a wave tank at Flanders Hydraulics Research, Antwerp, Belgium, to characterize the wave overtopping and impact force on vertical quay walls and sloping sea dike (1:2.5) under very oblique wave attack (angle between 45° and 80°). This study was triggered by the scarce scientific literature on the overtopping and force reduction due to very oblique waves since large reduction is expected for both when compared with the perpendicular wave attack. The study aimed to compare the results from the experimental tests with formulas derived from previous experiments and applicable to a Belgian harbor generic case. The influence of storm return walls and crest berm width on top of the dikes has been analyzed in combination with the wave obliqueness. The results indicate significant reduction of the overtopping due to very oblique waves and new reduction coefficients were proposed. When compared with formulas from previous studies the proposed coefficients indicate the best fit for the overtopping reduction. Position of the storm return wall respect to the quay edge rather than its height was found to be more important for preventing wave induced overtopping. The force reduction is up to approximately 50% for the oblique waves with respect to the perpendicular wave impact and reduction coefficients were proposed for two different configurations a sea dike and vertical quay wall, respectively.

Highlights

Populated coastal zones with very low freeboards are common worldwide (e.g., Belgium, The Netherlands, Vietnam)
The measured average wave overtopping has been compared with the predicted values using the existing formulas
The present study describes the setup and the results of physical model tests carried out at FHR on wave overtopping generated by perpendicular and very oblique waves, based on the generic configurations and conditions at Belgian harbors

Summary

Introduction

Populated coastal zones with very low freeboards are common worldwide (e.g., Belgium, The Netherlands, Vietnam). Often the flood protection is provided in these zones by the sandy beaches, but when it is insufficient or in the case of harbors, the most common solution is storm wall construction. A storm wall is located on top of the crest of a quay or a dike at a certain distance from the seaward edge of the crest, providing additional protection against the overtopping waves. The waves runup in form of a bore along its crests before reaching the wall. This flow is turbulent, and its velocity is decreased along the crest width. The distance between the edge of the structure and the storm wall is important because it characterizes the wave impact on the storm wall and overtopping over the storm wall

Methods

Results

Conclusion