Momentum Balance Across a Barrier Reef

Barrier reefs exhibit distinct hydrodynamic behaviors that contrast with sandy beaches and fringing reefs, according to a combined experimental and numerical study conducted over the Ouano reef barrier in New Caledonia. The research reveals that cross-reef currents induced by wave breaking significantly influence momentum budgets, particularly through frictional processes. Unlike classical beach behavior, where radiation stress gradients balance barotropic pressure gradients associated with wave setup, barrier reefs transition to an open-channel regime dominated by frictional head loss. Numerical simulations using a non-hydrostatic wave-resolving model coupled with turbulence modeling highlight the vertical flow structure, showing a log-layer profile over the reef flat and an anticlockwise circulation under breaking waves on the forereef. These findings underscore the complex, depth-dependent hydrodynamic behavior of barrier reefs, particularly during extreme wave events.

Sous, D., Dodet, G., Bouchette, F., & Tissier, M. (2020). Momentum Balance Across a Barrier Reef. Journal of Geophysical Research: Oceans, 125(2). Portico. https://doi.org/10.1029/2019jc015503