摘要
This paper deals with an analysis of selected equations used for the determination of a stable longwise slope calculation of torrential rivers of Jajroud in east of Tehran. Irregularity of the gradient, accompanied by heavy bed-load experiencing abrupt changes of the flow as a result of heavy rainfalls of short duration and high intensity, these are typical features impacting the behavior and characteristics of torrential rivers. The determination of the stable bottom slope, when the river bed is kept unpaved but still provides resistance against harmful effects of rapids, becomes an essential objective of the study. Three methods are used to determine the stable slope： the first is based on tangent tension （shear stress theory）, the second observes a （critical） non-scouring cross-sectional velocity （critical mean channel velocities）, and the third applies the bottom layer velocity （the critical bed velocities）. The mathematical hydraulic model HEC-RAS v. 3.1.3 has been used for the verification of the methods in this research study.
