A numerical–empirical approach for evaluating morphodynamic processes on gravel and mixed sand–gravel beaches

Pedrozo-Acuña et al. [Pedrozo-Acuña, A., Simmonds, D.J., Otta, A.K. and Chadwick, A.J., 2006. On the cross-shore profile change of gravel beaches. Coastal Engineering, 53(4): 335–347] presented a numerical–empirical investigation of the processes that control sediment transport in the swash zone on steep gravel beaches. This was based on a sensitivity analysis of a sediment transport/profile model driven by a highly non-linear Boussinesq model [Lynett, P., J., Wu, T.-R. and Liu, L.-F., P., 2002. Modelling wave run-up with depth-integrated equations. Coastal Engineering, 46: 89–107] which was compared to near full-scale measurements performed in the GWK flume in Hanover. In this paper we have extended our analysis to compare these earlier results with those relating to a mixed sediment (gravel and sand) beach. The parametric sensitivity analysis also incorporates a discussion of the effects of acceleration about which there is much debate. The sensitivity analysis suggests that fluid acceleration can contribute to the onshore movement of sediment that causes steepening of initially flat beach faces composed of coarse sediment. However acceleration alone cannot be the cause of the observed berm growth during the GWK tests. Instead, a complex balance of processes is responsible for the profile evolution of coarse-grained beaches with no single dominant process.