An in-house two-dimensional Shallow Water Equation (SWE) model has been updated, calibrated and applied to simulate various complex hydrodynamic and morphodynamic situations including waterways, recirculating flows and tide induced sediment transport. In the applications presented herein, the sediment transport and bed evolution model is calibrated to predict the transport of non-cohesive and cohesive sediments. The prediction of total sediment transport, bed shear, flow velocity, sediment characteristics, sediment fractions, parameterization of hydrodynamic calibration coefficients and flow depth rely on empirical relationships. Tide generated currents within the estuaries are driven by the tidal range over the open ocean, the tidal volume of the estuary and its interaction with the bed. The influence of tidal asymmetry on the residual sediment transport is the dominating factor in the pattern of bed level change and direction of sediment transport. River flows have the dominant effect in the upper reaches of an estuary with tidal flows being dominant in the middle and outer regions. With the utilisation of numerical methods by means of hydrodynamic equations for solutions to unsteady flows, mathematical modelling has become an effective and economic way to obtain the required hydraulic parameters which gives a significant contribution to the prediction and understanding of the hydrodynamics and morphodynamics inside an estuary compared to the high costs involved in performing field investigations. The accuracy in the sediment flux evaluation and bed level change predictions is dominated by errors in the physical properties and the limitations of the empirical total load formulae.
A comprehensive study has been carried out to enhance the process of model calibration and validation in application of shallow water equations to model coastal areas and estuaries with a specific focus on hydrodynamics and morphodynamics. The usual calibration parameters, viz., horizontal eddy viscosity coefficient,  and bottom friction coefficient, Kbr, are considered for this purpose in a SWE based research code. It is brought out that the usual method of constant parameterization using water level data alone might not be sufficient to ensure a statistically acceptable prediction of hydrodynamics and morphodynamics. The study demonstrated that the flow parameters are better predicted closer to the field observed values by implementing a spatially varying  expressed as a function of depth averaged velocity and length scale of computation mesh. The predictions are further improved by parameterizing the Kbr as a function of depth. Such an approach improves computational efficiency by avoiding repeated trial and error methods and produces more realistic flow features and morphodynamic predictions. This study contributes to the knowledge by proposing a new and simple approach in parameterizing the horizontal eddy viscosity, the efficiency of which is validated with the field data. The contribution of spatially varying bottom friction coefficient in improving the results is also investigated and discussed.
The equations to be adopted for the sediment transport calculation form an integral part of the morphodynamic models. The exercise of arriving a suitable total sediment transport formula to be employed in bed evolution or morphological model, for a given hydrodynamic set up (macro-, meso-, or micro-tidal estuaries), forms an integral and challenging part of morphodynamic modeling. A comprehensive study to understand the functionality of the different parameters of total sediment transport equations led to the identification of suitable total sediment transport formula, among the literature, for different tidal regimes. The accuracy of the predictions is evaluated with field measurements based on several statistical approaches. A new, robust and simplified formula for predicting the total sediment transport load for estuarine and coastal processes is proposed. The formula is an explicit relationship among the total sediment transport quantity, sediment size, bed shear, flow depth and flow speed and is applicable over all tidal regimes. Along with these empirical relations, additional sub-models like pick up model and sediment deposition model also contribute significantly to the calibration of the morphodynamics of rivers and estuaries. In this study, pick-up and drop functions suggested in literature are evaluated based on their contribution in modeling the bed level change. The efficiency of different pickup and drop functions in morphodynamic predictions are evaluated.