A field study was performed at a site in San Pablo Bay, California, to evaluate how well suspended sediment distribution equations reproduce observed concentrations. Near-bed measurements of current velocity, suspended sediment concentrations, and fluid and particle characteristics were made. An in-situ settling cylinder was used to determine settling velocity values of aggregated suspended sediments and photographs from a plankton camera provided size estimates. In-situ weighted average settling velocities were generally an order of magnitude greater than a weighted average for Stokes calculations of settling velocity for the grain-size distribution of the reference suspended sediment sample and two orders of magnitude greater than a Stokes settling velocity for the median grain size of suspended sediment. Flocs were commonly ∼ 100 μm in diameter, and as large as 450 μm, with settling velocities as high as 0.2 cm s −1. Calculated suspended sediment concentration profiles using in-situ estimates of settling velocity yielded closer agreement with observed concentration profiles (within 25%) than using settling velocities calculated from the grain-size distribution of suspended sediment samples (within 40–50%).