Influence of horizontal eddy viscosity and bottom friction coefficients on morphodynamic evaluations

Abstract

The horizontal eddy viscosity (ε) and bottom friction coefficient (Kbr) are important hydrodynamic parameters in the computation of flow fields that dictate the morphodynamics. The effect of the variations in ε and Kbr as well as their combination on the prediction of hydrodynamics and morphodynamics in the Cochin harbor and adjoining nearshore area (9.9312° N, 76.2673° E) has been investigated in detail. A tidal circulation model to solve the shallow water equation is applied with the different parameterizations of ε and Kbr. In order to understand its effect, ε is expressed as a function of depth averaged velocity and length scale of computation mesh, whereas Kbr is expressed as a function of depth. The validation of the model is carried out with the measured currents. The improvement in the hydrodynamic and morphodynamic predictions is demonstrated by implementing the spatially and temporally varying ε The predictions are further improved by implementing a spatially varying Kbr. It is seen that the simulations with varying ε and Kbr predict the morphodynamic behavior close to the field values. The performance of the model predictions is discussed in terms of R2, RMSE and BSS (Brier Skill Score).