Do longshore bars shelter the shore?

Abstract

In most past theories on Bragg reflection of waves by a finite patch of rigid bars, only outgoing waves are allowed on the transmission side, simulating the effect of an idealized shoreline where all the incident wave energy is consumed by breaking. In these theories the amplitudes of both the incident and reflected waves are found to decrease monotonically over the bar patch in the shoreward direction. This result has motivated the idea of artificially constructing bars to protect a beach from incident waves. However, some numerical calculations have suggested that this tendency does not always hold when there is some reflection from the shore. We show here that with finite reflection by the shoreline the spatial distribution of wave energy over the patch can indeed be reversed, indicating that the mechanism can increase the hazards to the beach. The phase relation between the bars and the shoreline reflection is found to be the key to this qualitative change of wave response.

Wave modelling – The state of the art

“…in cases with waves propagating over nearshore sand bars and reflecting over the beach (Yu and Mei, 2000). Except for such conditions, the evolution of wave action over scales larger than the bottom autocorrelation length, is very well predicted by S bscat , in agreement with phase-resolving models for wave propagation in one dimension (Mei, 1985;Kirby, 1988).…”

Wave Propagation over a Submerged Bar

“…Groesen and Andonowati [3] show similarity between optic and water waves based on the same model. Yu and Mei [4] studied waves over a bar by including the effect of the reflection from the beach. Other references can be found by reading the review paper in [5].…”

Real time hybrid modeling for ocean wave energy converters

“…For example, a given incident ocean wave spectrum loses its energy quite fast if it moves over a muddy seabed [18][19][20], while over a rocky seafloor it can propagate long distances with minimal attenuation and damping. Or, the shape of the coastline and the beach's reflection coefficient may substantially change the wave pattern and the energy density near the shoreline [27]. The presence of the energy harvester may itself change the dynamics of the interactions in unexpected ways by, say, absorbing marine life or trapping sediments.…”