EFDC+ contains a fully integrated propwash module that predicts bottom velocities, bed shear, and sediment resuspension using ship information, position, and speed, dynamically coupled to the three-dimensional hydrodynamics of the waterbody. It has application for contaminated sediment remediation sites where ship traffic and associated propwash impacts are observed and allows more integrated propwash assessments for port and harbor engineers, essential when evaluating impacts to a foundation or bulkhead due to propeller action, as well as harbor maintenance dredging.

A propeller jet is far smaller than a typical model cell, so resolving it on the model grid would mean building a grid too fine to run. EFDC+ instead computes each ship’s propwash effects including flow velocity, shear stress, and erosion rate on an independent sub-grid representing the jet area behind the vessel, then links those results to the model grid cells at every time step of the hydrodynamic and sediment transport computation.

This is what makes propwash assessment practical at port scale. You keep a grid sized for the harbor while still resolving the jet that does the scouring.

Quickly load and process Automatic Identification System (AIS) data from U.S. government sources such as MarineCadastre.gov or from commercial operators. AIS relies on a ship’s Maritime Mobile Service Identity (MMSI) code, which can be downloaded along with time, position, course, heading, and speed for easy importing into EEMS.

Load the physical characteristics of ships from a number of online databases to populate the EEMS ship database with information such as the dimensions and tonnage of each vessel. Where data isn’t available, you can estimate and enter values manually, giving an accurate picture of ship movement in a port or other area of interest.

The propwash module dynamically links the hydrodynamic grid, ship paths, the velocity field, the propwash approach based on Maynord (1990, 2000) and Hamill (2016), and the modules for bottom shear, erosion flux, sediment transport, and sediment-bound toxics transport. Contaminated sediment may be entrained and then transported by currents induced by vessel traffic, which means propwash affects the cleanup of contaminated sediment sites, whether through dredging, capping, or in-situ treatment.

[EFDC+] Fast settling handles a process unique to this setting. The energetic, turbulent propwash plume erodes cohesive beds in chunks rather than as discrete particles, and those chunks settle faster than uniformly eroded material. EFDC+ represents them as separate fast-settling classes in SEDZLJ, fully integrated into the chemical fate module as well, so mass-eroded material behaves realistically instead of being smeared through the water column.

Optionally, the momentum carried by the propeller efflux can be added to the 3D flow field as a source term, so the hydrodynamic solution includes the ship’s own wake when it computes the next time step.

EFDC+ resolves the efflux velocity into grid-oriented components using the angle between the ship’s heading and the grid rotation, then distributes the resulting momentum across the water layers the propeller intersects, based on ship draft, propeller diameter, water depth, and layer structure. A user-defined momentum effect factor accounts for losses and turbulence not directly simulated, since the actual efflux plane can be smaller than the propeller face area.