CMS-Flow is a coupled time-dependent circulation, sediment transport and morphodynamic model based on the numerical solution of the mass, momentum and transport equations on a Cartesian (quad-tree) grid network with both explicit and implicit solvers. It has been developed and is currently supported under the Coastal Inlets Research Program (CIRP) conducted at the U.S. Army Engineer Research and Development Center (ERDC), Coastal and Hydraulics Laboratory (CHL). The model's primary function is to support multi-disciplinary research teams and conduct practical projects at coastal inlets. CMS-Flow has been designed with a relatively simple code structure which allows for rapid development and inclusion of new sediment transport algorithms, while always being accessible to the general modeling community, including both USACE and commercial users. Today, CMS-Flow is an integral component of the CIRP, providing technology for simulating hydrodynamics, waves, sediment transport and morphology for short and long timeframes in coastal inlets, adjacent beaches, navigation channels and bays.

,Ocean City Inlet, Maryland, is a dual-jetty inlet with a well-documented ebb shoal complex. During 2002, the south jetty was raised and sand tightened, and surveys in 2004 and 2005 show seaward radial migration of the outer ridge of the ebb shoal in response to the jetty rehabilitation. Natural sand bypassing occurs by transport from north to south. The ebb shoal contains a sand tongue on its northern extent that is maintained primarily by the ebb jet as it sweeps from south to north. Thus, transport that maintains the sand tongue is in the opposite direction from the natural bypassing, and growth of the sand tongue on its northwestern tip impinges on the navigation channel. Numerical modeling of tide and wave-driven circulation and sediment transport reproduces the morphologic processes that occur at Ocean City Inlet, and early modeling identified the sand tongue as a potential beach fill borrow site for mechanical bypassing to Assateague Island, as removal of sand there would not directly interrupt the natural bypassing pathway, and the material is not a source for Ocean City beaches to the north.

: This report, the second in a series, describes upgrades of the two-dimensional circulation model CMS-M2D developed under the Coastal Inlets Research Program (CIRP) conducted at the U.S. Army Engineer Rsearch and Development Center, Coastal and Hydraulics Laboratory. The upgrades chiefly concern capability to calculate sediment transport and morphology change at coastal inlets, navigation channels, and adjacent beaches. CMS-M2D is operated as part of the CIRP's Coastal Modeling System (CMS) that couples calculations of wave transformation, circulation (horizontal currents and water surface elevation), sediment transport, and morphology change. The coupling is interactive and accomplished within a graphical user interface called the Surface-water Modeling System (SMS). Within the SMS, the CMS contains menus and steering modules that allow specification of input and output, as well as the time steps for and degree of interaction among the various processes. The SMS also contains utilities for viewing data and calculation results, monitoring progress of simulations, and running of project level CMS-M2D applications with tidal and surge forcing as provided by a regional circulation model. CMS-M2D is computationally efficient, easy to set up, and has features required for many coastal engineering applications at coastal inlets and at the bays and beaches adjoining inlets. Example features include robust flooding and drying, wind-speed dependent (time-varying) wind-drag coefficient, variably-spaced bottom-friction coefficient, time- and space-varying wave-stress forcing, efficient grid storage in memory, and two hot-start options. Three sediment-transport formulations are available for selection by the user, two involving total load formulations and one involving calculation and transport by bedload and suspended load in an advection-diffusion equation approach.