Estimating wave-Induced Bottom Velocity in the vicinity of reflective structures

The undertow, the seaward return flow of wave mass transport, induces a seaward stress on the bottom sediment particle. A nonlinear theory equation is presented for estimating the vertical andhorizontal distribution of undertow in the surf zone for reflective beaches. The present model is amodification of the original model presented by Okayasu et al., (1990) for natural, non-reflective beaches wherein the wave set up, radiation stress and mass flux due to breaking waves are modified as described by Mehrdad and Neshaei (2004) to include the effect of partially reflectedwaves. Furthermore, the nonlinearity of waves is provided by Fenton's Fourier series theory andthe wave-current interaction in calculation of undertow is applied. Also, the nonlinear mass driftof the incident wave is included in the proposed model. The results of experimental investigationand model development show that existence of reflective conditions on beaches results in a reduction in the magnitude of undertow and modifies its distribution across the beach profile

Keywords:

Nonlinear wave , reflective structure , undertow , wave-current interaction