Deposition on floodplains delays the downstream movement of particles transported by rivers, increasing the time required to improve water quality in downstream receiving waters following watershed restoration schemes designed to reduce upstream sediment loading. We present equations to assess whether floodplain storage is likely to influence the timing of sediment delivery, for estimating mean travel times, and for determining complete travel time distributions. We use a step reduction in upstream sediment supply to represent expected effects of best management practices, and present an analytical solution for the time needed to deliver restoration benefits downstream. Parameters required by these equations can be extracted from sediment budgets and estimates of the ages of floodplain deposits. Illustrative computations for the mid-Atlantic region predict that only 15% of the sediment load can be transported 200 km without being stored on a floodplain. Once deposited, particles remain in place for ~300 years, leading to average transport velocities of only ~100 m/yr. For distances of 20-75 km, average travel times range from ~500 to ~750 years. These results suggest that Best Management Practices employed in the headwaters of large watersheds will not benefit downstream estuaries within the decadal timescales typically considered by watershed managers. Precise predictions, however, will require accurately measuring floodplain deposition, erosion, and sediment chronologies throughout watersheds, data that are currently unavailable.