Influence of artificial sandbar on nonlinear wave transformation: Experimental investigation and parameterizations

Wave nonlinearity is a main driving force for near-bed sediment transport, and thus affects the beach evolution. Accurate prediction of wave nonlinearity is an essential need for the design of beach nourishment and restoration projects. So far, wave nonlinearity evolution patterns on the nourished beaches with abrupt changes of bottom slopes and water depth are not fully understood. This paper presents experimental results of nonlinear wave transformation across the submerged artificial sandbar. It can be found that the artificial sandbar intensifies wave shoaling processes and increases the magnitudes of the wave nonlinearity. Wave skewness and asymmetry are parameterized and both dependent on Ursell number and bottom slopes. By taking bottom slopes into consideration, the prediction accuracy for wave skewness is improved 17% with dataset measured in this study and 21%-65% with an independent dataset, compared with a common-used formula also calibrated on a steep low-crest breakwater without considering the bottom slope. Wave skewness decreases with increasing Ursell number in the inner surf zone, indicating the artificial sandbar influences its shoreward wave nonlinearities through the wave history. Finally, it is found that wave triads interactions can be enhanced by the steep seaward slope and small water depth of the artificial sandbar.

Automated summary

This paper presents experimental results of nonlinear wave transformation across a submerged artificial sandbar. The results show that the artificial sandbar intensifies wave shoaling processes and increases the magnitudes of wave nonlinearity. By considering bottom slopes, the prediction accuracy for wave nonlinearity is improved.