The erosion of the seabed in front of coastal structures induced by waves can lead to multiple types of failure instability or function of the structure. On this topic most research has been done into erosion in front of vertical structures. For sloping structures a knowledge gap exists in the understanding of the processes that lead to erosion of seabed material directly in front of the structure. In this report the structural and hydraulic paramters that influence the development of a scour-deposition pattern in front of sloping structures is tested. For this model tests have been done in the wave flume of the laboratory of Hydraulic Engineering at Delft University of Technology. This has resulted in a design formula that can be used for a first estimation of the maximum scour depth in front of sloping coastal structures where bed-load transport is dominant. Parameters that are used in determining this depth are the number of waves, the incident significant wave height, the relative water depth and the reflection coefficient of the structure. Performance of the formula with the model test results is good.

“During the last safety assessment of Rijkswaterstaat in 2006 the Afsluitdijk failed on the current safety standards regarding flood protection. A new design was needed which ensured continuous protection against flooding in the future. Large scale and small scale tests are performed to optimize the design. Clear differences in the average wave overtopping discharge are observed between large and small scale. The new design of the Afsluitdijk has a complex geometry and consists of new types of elements of which not much information about the roughness of these elements is available. Also, the combined effect of roughness elements and berm has not been fully investigated yet. This asks for a more accurate method to predict the average wave overtopping discharge for composite slope. Various adjustments to current theories are proposed for this type of structure. “