Discharge Prediction in Smooth Trapezoidal Free Overfall—(Positive, Zero and Negative Slopes)

This paper presents a calibration curve using dimensionless parameters $[{\mathrm{Qm}}^{1.5}/(\sqrt{g}{B}^{2.5}\left)\right]$ and $[e^{5.5\left(\mathrm{SO}\right)}{\mathrm{mY}}_e/B]$ for the prediction of discharge $\left(Q\right)$ with the help of known end‐depth $\left(Y_e\right)$ and vice versa. The curve is based on published experimental data of different investigators for smooth trapezoidal free overfall in horizontal as well as sloping channels (both positive as well as negative slopes). The curve, best fitted to the data, shows an excellent agreement between the observed and predicted values of discharge with a correlation coefficient $\left(C_R\right)$ equal to 0.99753. The regression equation of the calibration curve has, also, been tested for unused data and an excellent agreement is obtained between the two. Furthermore, it is also observed that for horizontal channels, the theoretical value of the constant (i.e., slope) in the equation of the straight line $X_e=\left(\mathrm{constant}\right)\left(X_c\right)$ is greater than that obtained from the present investigation based on experimental data, where $X_e={\mathrm{mY}}_e/B$ and $X_c={\mathrm{mY}}_c/B$. The constant obtained in this work gives better results as compared to that obtained in previous research.