evaluation of trap efficiency and initial unit weigth of deposited sediment in reservoir dam

Dams build on the river for storage of water, flood control and hydropower. They result vitial effection on the man society. Economic factors result the useful lifetime to be long, for this purpose have to study incoming sediment and coefficient sedimentation (trap efficiency) for this reservoir and effective factors exactly in the empirical and t heoric methods. Dam trap efficiency explain the percent of incoming sediment retained in the reservoir. Because of rate reservoir incoming sediment explain in weight unit for estimate sediment volume to need specific weight of sediment. In the present study estimated trap efficiency and specific weight of sediment retaintion in the reservoir at fifteen dams of our home by using of information daily discharge, samples of discharge – sediment in the upstream and downstream stations of this dam, result of surveying sediment reservoir, sediment samples retained in the reservoir and virgin specific weight samples. Then result of observation trap efficiency compare with estimation of Brown, Churchill, Brune and Chen method. Base of this empirical methods is the hydraulic reservoir characteristics , sediment and watershed characteristics. At last the result of Brown method shows at least difference with observation data. Also observation first specific weight of virgin samples retained in the reservoir compare with Lane & Koelzer, USBR and Miller methods, base of this empirical methods is soil texture and operation method of reservoir. At last result of Lane & Koelzer method show at least difference with observation data. So the selected empirical methods suggest to apply for design reservoir dam.