Assessment of Estimation Methods of Stage -Discharge Rating Curve According to Bed Form Resistance Equations in Nekarud Ablo Hydrometry Station, Mazandaran

Stage -discharge rating curve is mainly developed from measured data in any hydrometry station. Measured data usually obtain in low to medium flow discharge, because in most cases it is very difficult to measure the flow discharge during flood. Therefore, the stage-discharge is extrapolated beyond the measured data to compute the flood which may estimate low or higher value. This is because during the high flow, the bed form is developed which causes the flow resistance to change. In order to establish a better stage - discharge rating curve, it is important to apply methods which consider the bed form resistance. In this research, Einstein-Barbarossa, Shen, White, Engelund and Brownlie methods were used to complete the final part of the Stage- discharge rating curve obtained from the measurement at the Ablo hydrometry station located on the nekarud river or to construct the Stage – discharge rating curve at the mentioned station. After collecting the required data including river cross section, discharge and related stage and bed material gradation in this station and calculating the corresponding Stage – discharge using the mentioned methods in the water year 2021-2022, various statistical comparisons were made between calculated and measured discharges. The results showed that the Einstein-Barbarossa method has the lowest absolute mean error of 6.9 and minimum root mean square error of 2.7 compared to other methods.