needed leads to improved accuracy for a given computational cost as compared to models that use
structured grid methods. However, both structured and unstructured grid method solutions to the
governing morphological equation can experience numerical robustness and accuracy problems
manifested in the form of spurious spatial oscillations, especially in the presence of steep
bathymetric gradients (see for example Johnson and Zyserman, 2002).
In this paper, we describe the development of a new unstructured grid morphodynamic
model system that uses a new class of highly accurate finite element methods for the solution of
the governing morphological equation. The hydrodynamic model component of our system is
provided by the well verified and validated unstructured grid model ADCIRC, developed by the
second author and a number of collaborators (Luettich and Westerink, 2004). ADCIRC is both a
two-dimensional, depth-integrated (2DDI) and three-dimensional (3D) free surface flow model.
In this paper, we focus specifically on the 2DDI ADCIRC model, which solves the shallow water
equations using the standard or continuous Galerkin (CG) finite element method in space. To
overcome well known problems in solving the shallow water equations using equal-order