Spectral Wave Dissipation Over a Roughness‐Varying Barrier Reef

Abstract

The present paper reports on a field experiment performed over a shallow, roughnessvarying barrier reef at Maupiti island, French Polynesia. The spectral wave energy balance is examined, outside the breaking zone and accounting for non-linear transfers and mean current, to estimate the wave friction factor. This latter varies from 0.05 to 4, with dependence on the ratio between near-bed orbital amplitude and roughness height well predicted by an adjusted parameterization from Madsen (1995). The present results are discussed with respect to other field data recovered on coral and rocky grounds.

Quantifying the topographical structure of rocky and coral seabeds

“…Maupiti is a diamond-shaped high volcanic island, located in the western part of the Leeward Islands, Society Archipelago, French Polynesia. The selected site has been documented, both topographically and hydrodynamically, by a series of recent field studies [ 12 , 20 , 49 ]. The reef barrier displays a nearly uniform along-reef structure but a striking cross-shore partitioning in terms of reef colony structure ( Fig 3C, 3D and 3E ).…”

“…Second, from a hydrodynamical aspect, the bottom roughness is a key driver of frictional dissipation which affects the momentum-related parameters, such as currents and water levels [ 11 , 12 ], and the propagation of the wave field which in turn controls the wave energy transfer and wave-induced impacts at the shore [ 13 – 15 ]. A few studies have performed combined analysis of wave propagation and fine seabed topographical measurements in order to draw relationship between the wave attenuation and the seabed roughness structure [ 16 – 20 ]. The common finding was that the dominant scaling of roughness structure is the standard deviation of the seabed elevation.…”

“…The common finding was that the dominant scaling of roughness structure is the standard deviation of the seabed elevation. However recent observations may lead to assume that other seabed parameters may affect bottom friction [ 20 ]. In this context, a core issue is the development of quantitative characterization of the seabed structure, a prelude to the implementation of roughness-metrics-based rather than empirical parameterizations of wave frictional dissipation over rough coastlines worldwide.…”

Coupled Short-Ig Wave Dunamics Over A Shallow Barrier Reef

“…The present study focuses on the data recovered over a single cross-barrier transect located in the south-west barrier of Maupiti Island, from 5 to 18 July 2018 (Figure 1). The recovered dataset has already been analysed in terms of momentum flux (Sous et al, 2022) and SW frictional dissipation (Sous et al, 2023) . The focus is here placed on the coupled SW-IG dynamics using bottom-moored pressure sensors deployed on the barrier.…”