Sediment transport is dependent on the hydrodynamic conditions. In general there are two types of sediment transport. Cohesive and non-cohesive. The cohesive is characterized by low settling velocities and long response times for hydrodynamic changes. Therefore the transport is dominated by the advection of the water column. For non-cohesive sediments the settling velocities are in general larger and the concentration profile will therefore quickly adjust to changes in hydrodynamics. As a consequence of this a major part of this transport will take place on, or very close to, the bed as bed load.
MIKE MT can take suspended transport of fine grained non-cohesive sediment into account. This is done by calculating an equilibrium concentration profile based on the sediment properties and the hydrodynamics.
The bed is assumed to erode as flakes which means that the distribution of fractions within the bed is also the distribution when eroded. This means that the erosion formula used in the MT section controls the maximum erosion of all fractions. After the flakes has been eroded it is assumed that they are destroyed or regrouped by turbulence. Since the sand fractions has no cohesive properties it will be freed by this and behave independently. The model does this by calculating the maximum possible equilibrium concentration for the given sand under the given hydrodynamic properties. If this is above the concentration of the sand fraction, the extra sand will be deposited so that the concentration is the equilibrium concentration.
For more information see MIKE MT Scientific Documentation.