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Attention is given to the properties of sediment beds over the full range of conditions ͑silts to gravel͒, in particular the effect of fine silt on the bed composition and on initiation of motion ͑critical conditions͒ is discussed. High-quality bed-load transport data sets are identified and analyzed, showing that the bed-load transport in the sand range is related to velocity to power 2.5. The bed-load transport is not much affected by particle size. The prediction of bed roughness is addressed and the prediction of bed-load transport in steady river flow is extended to coastal flow applying an intrawave approach. Simplified bed-load transport formulas are presented, which can be used to obtain a quick estimate of bed-load transport in river and coastal flows. It is shown that the sediment transport of fine silts to coarse sand can be described in a unified model framework using fairly simple expressions. The proposed model is fully predictive in the sense that only the basic hydrodynamic parameters ͑depth, current velocity, wave height, wave period, etc.͒ and the basic sediment characteristics ͑d 10 , d 50 , d 90 , water temperature, and salinity͒ need to be known. The prediction of the effective bed roughness is an integral part of the model.

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