1.
INTRODUCTION
The transport of sediment as bed load is an important process that occurs in rivers,
estuaries, and coastal regions. In many situations, this process and the resulting morphological
changes of the bed can have a detrimental impact on the coastal infrastructure and environment.
For example, dredged navigational channels and coastal inlets can be rendered almost entirely
useless by the accumulation of transported sediment. Returning these structures to operational
status, through dredging operations or the construction of jetties, represents a significant cost to
the agencies that maintain them. As another example, the structural integrity of bridges and piers
may be compromised due to excessive scour of the bed around abutments. In addition to these
infrastructure problems, there is host of environmental issues of concern, such as the transport of
pollutants with or as sediment, that can cause serious ecological damage. Accurate numerical
models that can predict sediment transport and the resulting bed morphology can help manage
these costly problems.
Clearly, the processes of sediment transport and morphological evolution of the bed are
determined by the properties of the fluid flow, which in turn are affected by the changes in the
morphology of the bed that they induce. Thus, the motion of the fluid and the motion of the bed
form an interdependent two-phase phenomenon that must be analyzed using a model system made
up of two distinct but interdependent model components: i.) a hydrodynamic component defining
the evolution of the flow, and ii.) a sediment transport/morphological component defining the
evolution of the bed. Such a modelling system is often referred to as a morphodynamic model. A
description and comparison of some existing morphodynamic model systems is given by
Nicholson, et al. (1997). Typically, these model systems use structured computational grid
methods. To a lesser extent, unstructured grid methods have also been implemented and can, in
fact, be highly advantageous based on their ability to provide local grid refinement near important
bathymetric features and structures. The ability to provide local grid refinement where it is
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