Introduction

EFDC_Explorer (Figure 1) is a Microsoft Windows™ based pre-processor and post-processor for the three-dimensional (3D) hydrodynamic model, Environmental Fluid Dynamics Code (EFDC), initially developed at the Virginia Institute of Marine Science (Hamrick, 1992 & 1996). The US Environmental Protection Agency (EPA) has continued to support its development. The EFDC code is public domain and part of a family of models recommended by EPA for environmental and regulatory applications (https://www.epa.gov/ceam/environmental-fluid-dynamics-code-efdc).

Figure 1 EFDC_Explorer Splash Screen.

EFDC is a general-purpose model for simulating threedimensional (3-D) flow, transport, and biogeochemical processes in surface water systems including: rivers, lakes, estuaries, reservoirs, wetlands, and near-shore to shelf-scale coastal regions. EFDC is capable of simulating cohesive and non-cohesive sediment transport, near-field and far-field plume discharge from multiple sources, and the transport and fate of toxic contaminants in the water and sediment phases. A dissolved oxygen/nutrient process (i.e. eutrophication) sub-model (HEM-3D) was added later (Park, et al., 2000). Special enhancements to the hydrodynamics of the code now include vegetation resistance, drying and wetting, hydraulic structure representation, wave-current boundary layer interaction and wave-induced currents. The EFDC code has been extensively tested and the code is currently used by many university, government, and engineering and environmental consulting organizations.

The EFDC model has been released in the past in various forms and versions. This user's manual focuses on only two versions, the 2010 GVC Version (EFDC_GVC) (Tetra Tech, 2007a, 2007b) and the EFDC DSI Version (EFDC+). The EFDC_GVC version has an implementation of the Generalized Vertical Coordinate (GVC) system (Stacey et al., 1995; Adcroft and Campin, 2004, TetraTech, 2006) that is supported in the current version of EFDC_Explorer.

This latest version of EFDC_Explorer continues to load input and output files from older versions of the EFDC model. However, after loading an older project into EE, users must save the project into a new folder before running the model. This is because the EFDC input files used by the latest EFDC+/EE are not always compatible with older versions of EFDC_DSI/GVC until EE updates them to the new format by saving the model. EFDC+ has been updated and expanded with a number of enhancements and new features that required the input files to be modified. For this reason, the user should also ensure that EE is correctly linked to the corresponding version of EFDC+ (see below).