Cumulative distribution of wave-current combined bottom stress

Cumulative distribution of wave-current combined bottom stress (blue dots) estimated from acoustic Doppler current-meter measurements at the wreck site, plotted in log-probability coordinates. The dashed red line represents a Gaussian distribution. The inset table lists the (approximate) frequency of exceedence (percent with smaller diameters) for grain diameters (mm) and associated critical shear stresses (τ_crit). The data indicate that bottom stresses are below the critical shear stress (τ_crit) for mobilizing carbonate fine sands with diameters of 0.15 mm about 84% of the time, and are below the critical shear stress for mobilizing the median grain size (1-mm granules) 99.5% of the time. No stresses were calculated that were capable of moving the coarsest 35% of bottom sediment.