The GETM model is a full 3D hydrodynamical model which uses the General Ocean Turbulence Model (GOTM) for the vertical turbulence structure. Spherical coordinates (expressed in latitude and longitude) are used in the horizontal plane, while sigma coordinates are used in the vertical (equidistant in shallow water and contracted near the surface and the sea bed in deeper water). The hydrostatic equations are solved on an Arakawa C grid in the horizontal using a mode splitting technique. Sea surface elevation at the boundary is derived from Topex Poseidon satellite altimetry data, and the model allows for the drying and flooding of tidal flats. For further detail cf. Burchard and Bolding (2002) and Stips et al. (2004).

The temporally and spatially varying suspended matter (SPM) concentrations are calculated as a function of the local sea-bed composition and wave-shear stress, with wave height and -period calculated from the wind forcing data using an equilibrium JONSWAP formulation subject to a shoaling function, and wave-orbital velocities calculated using linear wave theory. An improved SPM model is under construction (van der Molen et al. 2009).