الفهرس 
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Abstract
The oonstruotion of a dam across an alluvial river causes ,.i tal ohanges on the regime of sed1ment transport all the way along the river. Within the upstream zone, a reservoir is oreated and therefore the transport ability of the river is reduoed and aggradation takes place. Immediately below the dam, the released water is relatively clear and the sediment transport will be less than the natural transport ability of the river. ,This lack of sediment transport causes the river bed to degrade altering the regime of the river downstream.
Along the downstream reaches, the water section area is increasing due to the 1nc~ase of water depth and widening
ot the section due to bank erosion. Thus, the flow velocity is reduced and therefore both water surface slope and roug¬hness coefficient are changed. Generally, the water surface slope is flattening through the drop of water surface levels with different values along the reach and due to the lengthe¬ning of the flow thalweg by meander effects at some locations. The increase of friction coefficient is achieved through the combined action of bed armouring, where coarse material is available, and the for.mation of rougher bed configuration. Therefore, the degradation process will continue and the fin¬al regime is established when the combined effect of decrea¬sing the energy slope and increasing the bed roughness are sufficient to create flow conditions incapable of degrading more of the bed material all along the river reach.