Effect of Reflective Structures on Undertow Distribution

The study investigates the effects of reflective seawalls on wave breaking processes and mean flow distribution throughout the surf zone. The presence of reflective structures results in a significant change of wave breaking characteristics and turbulence structure in the surf zone. The organized large vortexes, which cause onshoreward mass transport, will also be changed thus changing the undertow considerably. The physical processes and mechanisms of wave breaking and turbulence structures in presence of a seawall have been investigated using visualization techniques. A model for evaluating the distribution of undertow in front of a reflective structure is also proposed on the basis of the change in wave fields due to the presence of reflected waves in the surf zone. The model is in reasonable agreement with the experimental results. It has been found that the presence of reflected waves due to reflective condition in the surf zone changes the wave breaking characteristics and reduces the magnitude of undertow. The results of the present work can be implemented for predicting cross-shore sediment transport models and beach evaluation models where reflective conditions exist.