Ecosystems Research Division

EFDC can simulate water and water quality constituent transport in geometrically and dynamically complex water bodies, such as vertically mixed shallow estuaries, lakes, and coastal areas. The EFDC model solves the three-dimensional, vertically hydrostatic, free surface, turbulent averaged equations of motion for a variable density fluid. The model uses a stretched, or sigma, vertical coordinate and Cartesian, or curvilinear, orthogonal horizontal coordinates. Dynamically coupled transport equations for turbulent kinetic energy, turbulent length scale, salinity and temperature are also solved. An optional bottom boundary layer submodel allows for wave-current boundary layer interaction using an externally specified high frequency surface gravity wave field. The EFDC model also simultaneously solves an arbitrary number of Eulerian transport-transformation equations for dissolved and suspended materials. For example, equations describing the transport of suspended sediment, toxic contaminants, and water quality state variables are also solved. Multiple size classes of cohesive and noncohesive sediments and associated deposition and resuspension processes and bed geomechanics are simulated. A complimentary Lagrangian particle transport-transformation scheme is also implemented in the model. The EFDC model also allows for drying and wetting in shallow areas by a mass conservative scheme. A number of alternatives are in place in the model to simulate general discharge control structures such as weirs, spillways and culverts. For nearshore surf zone simulation, the EFDC model can incorporate externally specified radiation stresses due to high frequency surface gravity waves. Externally specified wave dissipation due to wave breaking and bottom friction can also be incorporated in the turbulence closure model as source terms. For the simulation of flow in vegetated environments, the EFDC model incorporates both two and three-dimensional vegetation resistance formulations (Hamrick and Moustafa, 1995a). The model provides output formatted to yield transport fields for water quality models, including WASP5 and CE-QUAL-ICM.

Unique features of EFDC are its ability to simulate wetting and drying cycles, it includes a near field mixing zone model that is fully coupled with a far field transport of salinity, temperature, sediment, contaminant, and eutrophication variables. It also contains hydraulic structure representation, vegetative resistance, and Lagrangian particle tracking. EFDC accepts radiation stress fields from wave refraction-diffraction models, thus allowing the simulation of longshore currents and sediment transport.

Application History

The EFDC model has been used for a study of high fresh water inflow events in the northern portion of the Indian River Lagoon, Florida, and a flow through high vegetation density-controlled wetland systems in the Florida Everglades. The model has been used for discharge dilution studies in the Potomac, James and York Rivers. Salinity intrusion studies include the York River, Indian River Lagoon and Lake Worth. Sediment transport studies include the Blackstone River, James River, Lake Okeechobee, Mobile Bay, Morro Bay, San Francisco Bay, Elliott Bay, Duwamish River and Stephens Passage. Power plant cooling studies include Conowingo Reservoir, the James River and Nan Wan Bay. Contaminant transport and fate studies include the Blackstone and Housatonic Rivers, James River, San Francisco Bay, Elliott Bay and the Duwamish River. Water quality eutrophication studies include Norwalk Harbor, Peconic Bay, the Christina River Basin, the Neuse River, Mobile Bay, the Yazoo River Basin, Arroyo Colorado, Armand Bayou, Tenkiller Reservoir, and South Puget Sound. The Peconic Bay water quality application is particularly noteworthy. The model was calibrated using a one year data set and subsequently verified by simulation of an eight year historical period having extensive field data. The model was then executed for 10 year management scenarios to develop a Comprehensive Conservation and Management Plan for the estuary system.

For additional modeling information, please go to the EPA's Council on Regulatory Environmental Modeling (CREM) site. CREM promotes consistency and consensus within the Agency on mathematical modeling issues including model guidance, development, and application, and enhances both internal and external communications on modeling activities. The CREM is the Agency's central point to address modeling issues.

For information on models distributed by EPA's Center for Exposure Assessment Modeling (CEAM), please go to http://www.epa.gov/ceampubl/.

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