Analytical and Empirical Regime Relationships in Alluvial Rivers

It is vitally important that rivers reach an equilibrium state (regime). To be more precise, determination of stable hydraulic geometry is one of the most important factors on which designing, planning and training of rivers is based. In this research, an analytical model was proposed initially by using extremal hypotheses and then multivariate hydraulic geometry relationships were applied to the rivers under dominant bed load. Thereafter, field study was carried out on several gravel bed rivers in Khuzestan and Chaharmahal provinces. A total of 24 hydrometeorological stations in 17 river reaches were sampled to characterize bed material gradation curve. With regards to bed structure of gravel bed rivers, samplings were made by surface and volumetric methods. Then, sediment samples were put into two categories of surface and armor layers. The collected field data was originally applied to derive regime relationships by using multivariate regression analysis. The effect of bed structure was directly studied to better understand it in the regime relationships. A reasonable agreement was observed between the developed analytical and empirical exponents of the hydraulic geometry relationships in this study and those by other researchers. Finally, the developed model was calibrated using the field data of Iran and the mean relative error of the bankfull width and depth calculation were 26% and 24%, respectively.