2.3.5. Initial conditions

A dynamic model requires a set of initial values to be input in order to begin to solve the governing equations. The model needs a "best guess" set of conditions for all the nodes in the mesh at the beginning of the iterative process; a bad initial guess that is far from the real conditions will adversely affect the convergence, slowing down the process immensely. A commonly used strategy is to have the whole water body at rest with a constant water surface elevation (WSE) when t = 0. The real initial scenario generally emerges after running the simulation for a period from this initial state.

## 2.4. Parameters and data for the hydrodynamic model

Many different types of data are needed as input or to determine the controlling parameters when running a hydrodynamic model. The data used as direct input include the geographic coordinates of the shoreline, bathymetry, flow rate, water surface elevation, meteorological data such as wind speed and direction, radiation intensity, air pressure, precipitation and the evaporation rate, among others. In addition to the input data, data on the flow rate, velocities, water depth, and water surface elevation at other locations than the boundaries are also needed to calibrate the model to determine hard to measure parameters such as the roughness of the bottom and the horizontal momentum diffusion coefficient [16], and to confirm that the model accurately reflects the real scenario. The modeling results are compared to the data measured either in the laboratory or in the field for the model calibration and verification.
