Modelling erosion development during wave overtopping of an asphalt road covered dike

Abstract

Wave overtopping initiates erosion of dikes, thereby compromising the safety against flooding. Structures integrated in a grass covered dike may decrease the resistance against erosion. In this study, CFD modelling is used to assess the effect of an asphalt road on top of the dike crest on the initiation of erosion due to wave overtopping. The Reynolds-Averaged Navier-Stokes equations are solved via a k-ϵ turbulence model. Two wave overtopping experiments are used for validating the hydrodynamics and the coupled hydrodynamic-erosion model. The amount of scour caused by overtopping waves is predicted by combining the shear stresses from the CFD model with an erosion model including grass erosion. Both the hydrodynamics and scour depths show good agreement with the measurements. Results show that a dike profile with a road on top of the crest is more vulnerable to erosion development than a bare grass covered dike profile. This is caused by a combination of the smoother asphalt section and the damaged berms at the transitions of the asphalt with the grass cover.