The calculation of sediment transport rates are based on the assumption that there is an unlimited supply of sand available and that the concentration profile is fully developed. The calculation only considers the local conditions and as thus the transport rates in the individual grid points can be considered independently.
The core of the sediment transport calculation model (STPQ3D) solves the vertical diffusion equation on an intra-wave period grid to provide a detailed description of the non-cohesive sediment transport in combined waves and currents.
The bed load and the suspended load are calculated separately, thus enabling a detailed analysis of the sediment transport.