Numerical models and simulation of sediment transport and deposition

A numerical model simulating sediment transport and deposition is an equation set describing the spatial and temporal evolution of a fluid flow carrying sediment over, and interacting with, an adjacent mobile particulate bed. Although literally scores of such models exist, each starting from quite different assumptions and incorporating quite different sedimentary processes, the most common and the focus of this entry are process-based models constructed with the mutual goals of prediction and understanding. Given water and sediment mass fluxes delivered to a geomorphic system through time, these numerical models are expected to accurately predict the total mass flux and character of sediment passing each point in the system at time and space scales appropriate for the application. To do so, each model must capture how changes in state variables of the fluid flow, the sediment transport, and the deforming bed influence one another through feedback loops. Each also must embody the physical processes thought to be relevant and consequently each is a conjecture about the dynamical behavior of the geomorphic system. Thus, for example, if the geomorphic system is a river channel reach of a given initial hydraulic geometry and sediment characteristics with a given sediment and water feed at the upstream end, the model in question should predict accurately the temporally evolving flux of water and sediment along the reach and the amount of bed erosion or deposition through time using conservation and rate laws that describe all the processes and their interactions. This entry describes the character, use, and limitations of this general class of sediment transport model. Channelized flows are emphasized, although much of the discussion also applies to sediment transport models of lakes and coastal oceans. Also, the emphasis here is on non-cohesive sediment transport because most models, if they address cohesive sediment at all, are still quite primitive in its treatment. Table N1 list some popular examples. …