Novel analysis of in-situ acoustic and optical data collected in a shallow, wave- and current-driven environment enabled determination of: (1) particle characteristics that were most affected by near-bed physical forcing, and (2) characteristic shear stress, τ_char, at which the rate of changes to particle characteristics were most pronounced. Results indicated that moderate τ_char values of 0.125 Pa drove changes in particle composition during summer. In winter, particle concentration effects were most affected at τ_char of 0.05 Pa, suggesting dominance of fluff layer resuspension. Changes to particle size were most relevant during a biologically productive springtime period, with initiation of particle disaggregation occurring most commonly at τ_char of 0.25 Pa. The values of τ_char determined from acoustic and optical data are consistent with laboratory-based measurements of critical shear stress for resuspension of site sediments, and with typical critical shear stress values for resuspension of cohesive sediments as reported in the literature.