Bottom Drag Coefficient on a Shallow Barrier Reef

The present paper reports of a field experiment over a shallow, roughness-varying barrier reef at Maupiti island, French Polynesia. The depth-averaged momentum balance is used to estimate the bottom drag coefficient C_d, which varies from 0.01 to 0.3, with dependence on both depth and reef structure. The depth effect on C_d is well predicted by a log dependency, as used in previous laboratory and fields observations. The present results extend the approach to a system with more wave exposure and higher roughness-to-depth ratio. Additionally, the statistical relationship between high-resolution reef topography and hydrodynamical parameters is discussed.