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C EDIMENT transport rates and sedi-*■ ' ment yields are generally integral facets of water resource projects. In many ephemeral streams, design infor mation to provide for sediment trans port or storage is essentially nonexist ent. This paper presents a method for estimating sediment design information and illustrates the importance of varia tions in streambed composition on sedi ment transport. Size distributions and settling veloci ties of sediments encountered in stream-beds vary widely. Thus, the fluvial be havior of sediment will depend on the spread of sediment sizes, in addition to mean size. In natural streams, complica tions arise in describing the sediments available for transport, because grain size varies from place to place and be tween bed and bank. Since rivers or streams are constantly sorting the sedi ment load, obtaining representative sam ples of the material available for trans port is difficult during periods with or without flow. In the highly influent stream chan nels, like these encountered in ephem eral streams of the Southwestern United States, sediment often moves in a step-wise manner because of transmission losses. Water from storms originating in the upper reaches of a watershed is often completely absorbed in the chan nel before reaching the outlet. Thus, the water absorbed in the streambed reduces the ability of the stream to transport the sediment removed from the land surface or from the channel itself. The sediment deposited on the streambed is later picked up by flow from subsequent local storms combined with upstream storms (also by runoff from unusually large storms) and moved until the water is again lost or until it Article was submitted for publication in April 1974; reviewed and approved (or publi cation by the Soil and Water Division o