The upper reaches of the Susitna River have been considered for development of a large power generation system for south-central Alaska. Sediment and hydraulic data obtained from October 1984 to September 1985 (water year 1985) at selected sites on the Susitna, Chulitna, Talkectna and Yentna Rivers are summarized. Sediment data include measurements of suspended sediment and bedload discharge, and analyses of particle size distribution of suspended sediment, bedload, and bed material; hydraulic data include measurements of channel width, average depth and velocity of water, and water surface slope. Relations between water and sediment discharge are developed for each site. Sediment loads for water year 1985 were estimated for the Yentna , Chulitna, and Talkectna Rivers and for three sites on the Susitna River. About 31 million tons of sediment were transported to the Susitna River at Susitna Station during the year. The Yentna and Chulitna Rivers contributed about 21 million tons of sediment to the Susitna River. (Author 's abstract)