Bottom stress measurements in shallow water under waves

In the constant stress part of the bottom boundary layer, from 0.1 to 2 m above the bottom, waves can bias the measurement of average correlation of streamwise and vertical velocity fluctuations due to tides and wind, the Reynolds stress. From four vector velocity sensors in 15 meters depth exposed to ocean swell and wind waves, the differencing technique of Trowbridge has been used to remove the wave bias. However determination of the wave boundary layer stress of the lowest centimeter, responsible for sediment erosion and suspension, remains elusive.