Unsteady Stage-Discharge Relationships for Sharp-Crested Weirs

International audienc

Closure to “Unsteady Stage-Discharge Relationships for Sharp-Crested Weirs” by Firouz Ghasemzadeh, Salah Kouchakzadeh, and Gilles Belaud

International audienceThe discusser is highly acknowledged for his interest in the paper and for presenting valuable analytical work to highlight the deviation between steady and unsteady flow rate of an orifice installed at the invert of a tank. A majority of previous related research studies, as mentioned in the original paper, claimed that the steady-state rating curve of sharp-creased weirs could be used in unsteady flow. Accordingly, the main objectives of the original paper were (1) to highlight the deviation between the stage-discharge curve of the two flow conditions, and (2) to report and justify the transposition of the looped stage-discharge curve in the weir flow condition compared to that typically observed in streamflows.The discusser, by developing an analytical solution for his studied case, agreed to the first point raised by the authors, which indicates the importance of studying the impact of unsteady flow conditions on discharge measurements, which calls for further studies. However, the transposition of the stage-discharge in the looped curve, i.e., the second point, has not been observed in the discusser’s work. The writers believe this could be attributed to the fundamental differences between the two studied cases as discussed herein

Using Nonlinear Modeling to Predict Peak Discharge and Average Breach Width from a Breached Embankment

Some statistical models have been studied to predict peak discharge and average breach width from a breached embankment dam based on past dam failure data. The suggested models peak discharge Qp, has related to average width of the embankment Wavg, water volume above the breach bottom at the time of failure Vw, height of water above the breach bottom at the time of failure Hw, height of the embankment above the breach bottom Hb. Our models are presented with different independent variables for peak outflow prediction. In addition, average breach width Bavg, has related to Vw and Hb besides failure mode for empirical model. A comparison between the estimated with actual data shows reasonable agreement to proposed models

Spatially varied flow impact on resistance in corrugated pipes

The roughness coefficient is a significant factor in hydraulic design process, but carries vast uncertainty in practice. This paper reports the resistance coefficients of corrugated PVC pipes under different flow regimes (i.e. pressurised, gradually varied flow (GVF) and spatially varied flow (SVF) with increasing discharge). The investigated corrugated pipes are mainly used in subsurface drainage systems and carry a SVF. The influence of SVF on the roughness coefficient of such pipes has not yet been reported. The pipes were first examined to determine the roughness coefficient for pressurised flow. The influence of GVF and SVF was then studied. The results show that pipes behave differently in different flow regimes and the impacts of each flow condition on the flow resistance are reported here