A Study of Rating Curve and Flood Routing using Numerical Method

Abstract

The stage discharge curve, depth-averaged velocity and boundary shear stress distributions are essentially determined for the flood extenuation scheme. The difficulties aroused in prediction of these parameters are usually due to the 3D nature of the fluid flow in open channel. The current study represents different analytical model for velocity distribution, boundary shear stress and stage-discharge curves and their application to the trapezoidal compound channel. The analytical solution to the depth-integrated Navier-Stokes equation is used for the same and their results are validated using experimental data. These parameters are not easy to predict because of the three-dimensional characteristics of the flow field. The model proposed by Shiono and Knight (1988, 1991) is compared with those by Ervine et al. (2000), Kordi et al. (2015) and K-ε model (ANSYS) through numerical modelling. This test shows that secondary flow parameter plays a vital role and its significance proliferates near side slope where momentum transfer from the main channel to flood plain is observed. The contrast in the results are shown with the help of lateral variation in percentage error.

The flood routing is an important technique to determine the flood peak attenuation and the duration of the high water levels through channel routing. Beside stage-discharge curve, hydrographs also plays a vital role in flood prediction and forecasting. The present study shows the application of hydrological methods for channel routing, the constant coefficient Muskingum-Cunge (MC) methods on the River Brosna, Co. Offaly in Ireland. The results obtained are validated by two software packages MIKE 11 and HEC-RAS beside that the method ensuring the mass balance of the model is tested in terms of water storage. The results of all the tests are plotted and verified with respect to the mass conservation criteria. Data sets of the River Brosna, Co. Offaly in Ireland is taken from the Elbashir (2011) for the November 1994 flood event.