Evaluation of Stage–Discharge Relationships in Alluvial Rivers (Case Study: Shahroud River, Qazvin province, Iran)

Abstract

Many rivers are classified in alluvial rivers. Stage–discharge curve of these rivers is reliable just in measured conditions and for the sections by the use of measured data. Most of the stage–discharge equations are not able to consider flow resistance, and it causes some errors in qualitative and quantitative modeling. Therefore, it seems necessary to determine the accuracy of stage–discharge curve methods in the river sections without hydrometric stations. In this study, Einstein and Barbarossa (Trans ASCE 117:1121–1132, 1952), Engelund and Hansen (A monograph on sediment transport in alluvial streams. Technical University of Denmark, Copenhagen, Denmark, 1967) and White et al. (A new general method for predicting the frictional characteristics of alluvial streams. Report No IT 187. Hydraulics Research Station, Wallingford, England, 1979) methods were investigated in four hydrometric stations in Shahroud River. To do so, after field data collection, the stage–discharge curve of studied hydrometric stations was obtained by the mentioned methods. Results revealed that effect of flow resistance factors increased in maximum discharge. Einstein and Barbarossa’s (1952) method enjoyed the most accuracy in the stations with ripple bed form and discharge less than 20 cms. By increasing discharge or changing the bed form, the accuracy of this method decreased, so in this condition Engelund and Hansen (1967) and White et al.’s (1979) methods showed reliable accuracy. In the rivers with anti-dune bed form, White et al.’s (1979) equation had the most accuracy. Additionally, evaluating the effect of bed form, discharge, bed slope and bed load sediment size indicated that all the methods are highly sensitive to discharge flow and river bed form; on the other hand, bed slope and bed load sediment size are not determining factors in choosing proper method for the development of stage–discharge curve in alluvial rivers.