Incorporating Nearshore Processes into ROMS

John C. Warner (1), Richard Signell (1), Christopher R. Sherwood (1), and Hernan G. Arango (2)

(1) U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole
(2) IMCS, Rutgers-The State University of New Jersey

Prediction of nearshore processes is important for coastal circulation, water quality concerns, shoreline change, and recreational safety. Nearshore processes are driven primarily by wind-generated waves that propagate shoreward. As water depths decrease the orbital motions of the waves impinge on the seafloor and modify the wave dynamics. The waves also drive a shoreward flux of momentum that is balanced by an opposing pressure gradient, and a shoreward mass flux that is compensated by an offshore undertow transport, all resulting in a modification of the vertical structure of the currents.

We are incorporating nearshore processes into ROMS. First we have included capabilities for wetting and drying which is essential for many shallow water estuarine processes and shoreline evolution. Second we have incorporated nearshore radiation stress terms into the momentum equations. We have based these algorithms on the Mellor (2003; 2004) formulation that provides a vertical distribution of the radiation stress terms. Comparison to other formulations such as the vortex-force representation (McWilliams et al., 2004; Lane et al., submitted) will be discussed. Finally we have coupled ROMS to the nearshore wave model SWAN using the Model Coupling Toolkit (http://www-unix.mcs.anl.gov/mct/; Larson, et al., 2004; Jacob et al., 2005). The toolkit provides a means to construct parallel coupled models from individual models. We will describe the methodology to incorporate all of these algorithms into ROMS and demonstrate the performance with several simple test cases.