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Fine sediment exchange between a stream and the surrounding subsurface influences downstream contaminant transport and stream ecology. Fundamental models for this exchange were developed on the basis of (1) the hydraulics of bed form‐driven advective pore water flow and (2) subsurface colloid transport processes. First, a model was developed to predict the advective flow induced in a sand bed by stream flow over bedforms. The resulting “pumping” exchange rate was calculated based on the streamflow conditions, bed form geometry, and bed depth. The pumping exchange of suspended sediment was then calculated by superimposing advective transport and particle settling in the bed and including the effect of physicochemical filtration by bed sediment. The filtration coefficient approach was used to predict the reduction in the concentration of transported particles. Both settling and filtration cause …