General EFDC+ Model Development Steps

Owned by Kester Scandrett
Last updated: 17 Jun, 2022
3 min read

It is imperative that an EFDC+ model be built step by step, with each step building on the previous step and increasing in complexity.  For example, the HEM3D water quality sub-model can only be developed after the EFDC hydrodynamics has been calibrated. The basic development steps are provided below. 

1. Gather Existing and/or New Data

  • Domain GIS/mapping coverages for reference and support grid development
  • Bathymetry
    • Highest available data density
  • Flows
    • Upstream river(s)
    • Ungauged tributaries
    • Groundwater
    • Point and non-point sources
    • Rainfall (optional)
    • Evaporation (optional)
  • Water levels
    • Levels should be tied to a vertical datum, if possible
  • Wind data
    • Wind speed
    • Wind direction
    • Best if these data are 15-minute or shorter duration averaged data from 1 to 10 second sampled anemometers.
  • Atmospheric data (for temperature modeling)
    • Pressure
    • Temperature
    • Relative humidity
    • Solar radiation
    • Cloud cover
    • Best if these data are hourly or of a shorter duration
  • Water column data for all constituents of interest
    • For sediment transport also need settling speeds and flocculation
    • Vertical concentration gradients, if exist
  • Sediment bed characteristics (horizontal and vertical)
    • Grain-size distributions
    • Sediment erodibility characteristics
    • Sediment thickness and hard bottom (e.g. rock)
    • Organic carbon characteristics
  • Kinetic rates and/or transformation process rates
  • Dissolved/sorbed partitioning characteristics

2. Review Data

  • Convert all location/elevation data to common horizontal and vertical datums
  • Convert all units to common/consistent units
  • Map and chart data to evaluate spatial and temporal patterns
  • Validate data to the appropriate quality levels
  • Check for outliers/invalid data

3. Develop a Conceptual Model

  • Integrating all the driving forces and characteristics of the system, develop a cohesive conceptual interpretation of how the system behaves relative to fluxes and transformations for the constituents of interest.

4. Select Mathematical Model

  • Using the data review and the conceptual model, select the appropriate mathematical tool(s)
  • EEMS is assumed for the purposes here

5. Build Grid

  • Use CVLGrid to build a curvilinear orthogonal grid, or
  • Use EE to create a Cartesian grid, or
  • Use EE to import a third-party developed grid:
    • SEAGRID
    • CH3D
    • ECOMSED
    • Generic 4-corner format
  • Add bathymetry to the model

6. Flow/Water Surface Elevation Model

  • Usually, this step can be done using a 1-layer model for quick turnaround
  • Apply Initial conditions
  • Build flow/open Boundary conditions
  • Ensure water balance
  • Calibrate flow rates/water surface elevations

7. Full Hydrodynamics (HYD)

  • Add vertical layers (if needed) using EE’s layer feature
  • Build Initial conditions for salinity, temperature
  • Build boundary conditions for salinity, temperature and winds (WSER) and atmospheric data (ASER – required for temperature modeling)
  • Calibrate to velocity patterns and water column data for salinity and temperature.  Time series at various stations and vertical profiles (if you need it and have the data).

8. Sediment Transport (SED/SND)

  • Add the level of detail required for your application.  WQ models usually need some TSS for light extinction analysis, so it is best to include at least a cohesive and/or a silt.
  • Build Initial conditions
  • Build boundary condition time series
  • Calibrate water column concentrations
  • Calibrate to net sedimentation rates and/or scour and deposition patterns, if available

9. Chemical Fate and Transport (TOX)

  • Only start toxics modeling once a calibrated sediment transport model is available
  • Build horizontal and vertical initial bed concentrations
  • Initialize water column concentrations
  • Configure sediment-toxics interactions
  • Configure organic carbon-toxics interactions
  • Set initial bed particle and porewater diffusion and mixing rates
  • Determine groundwater fluxes, if applicable
  • Calibrate toxics to bed concentrations and water column concentration

10. Water Quality (WQ)

  • Water quality can only be added to the model once the hydrodynamics and temperature is suitability calibrated. Due to the WQ/temperature interaction, temperature calibration will likely need to be adjusted.
  • Decide if you are going to use the full sediment diagenesis sub-model or a simple defined nutrient/DO flux series or constant
  • Decide the level of complexity of the WQ submodel
  • Decide how many algal compartments are needed.
  • Build Initial conditions
  • Build boundary conditions
  • Calibrate WQ Model

11. Conduct the Analysis with/or Based on the Final Model