Figure 1 shows the Initial Conditions frame tab that contains access to the functions that assign initial conditions (IC's) that may be applied for bottom elevations, water depths, and bottom roughness. This is done through the use of the Assign button in the pertinent frame.

Other water column parameters, sediment transport bed, salinity and bed thermal sub-model use a common approach to interpolate data onto the model grid. This approach is discussed in the following section.

Note that each input parameter also has Legacy setting frames. These are ways of making global adjustments to the data sets, through addition or multiplication of all the data. These are no longer required as EFDC_Explorer provides more capability through the Assign button. However, they are included in the EE interface so the user can make sure how they are being used in legacy models.

Figure 1  Domain Tab: Initial Conditions and Bottom Roughness

Apply Cell Properties via Polygons

EFDC_Explorer often needs to assign constant or spatially varying values across the entire model domain or within subsets for a variety of water column, sediment and other spatially variable parameters and concentrations. The Initial Conditions frames in the Domain tab: (Bathymetry; Depths/WS Elevation; Bottom Roughness) use the same process as the Salinity, Temperature, Dye/Age; Toxics, Sediment and Water Quality tabs, each containing an Assign button for: Surface Elevation, Salinity, Temperature, Dye, Bottom Elevations, Thermal Depth and Bed Temperature. Selecting any of these buttons will bring up the form Apply Cell Properties via Polygons. As shown in Figure 5 9. This form provides the general purpose horizontal spatial assignment function needed. However, this utility is context/parameter sensitive and displays different options and features, based on what the user requested and/or specified for data. Figure 2 shows an example of this utility for bottom elevation.

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Figure 2  Apply Cell Properties via Polygons.

The Poly File field is an optional field used to specify a polygon file (in P2D or DAT formats) that contains one or more polygons. Cells that are inside the polygon(s), using the Inside Cell Test options, will be adjusted according to the options specified in the Modify Options frame. If the Poly File is missing, EFDC_Explorer will use all of the cells in the model.

The XYZ File is an optional file that identifies the measured or otherwise determined data that the user wants to assign to the EFDC cells. Generally, this file is required unless the user is simply applying a constant to the cells or is applying an operator.

Under the Modify Options frame various functions and features will be displayed, based on what parameter or process the user is assigning or modifying. In this case (Figure 5 9), bathymetry is being assigned. The user can select either to apply an operator to the currently defined field or interpolate the data in the XYZ File to the selected cells (via the Poly File). Nearest neighbor approach is used to interpolate the horizontal spatial data onto the grid. If it is for the water column, the user must specify which layer this assignment is for, one layer or all the layers.
If data is spare the user is recommended to select the Interpolate Empty Cells option so that bathymetry for the whole domain is generated from interpolated data. The Other Options or Options button brings up a form allowing the user to change the interpolation options. Depending on whether bathymetry or wave parameters are being set the Option button also allows the user to define raw data zonation options. The zonation option simply automatically divides the raw data into a specified number of X and Y zones (with overlap to handle zone edges) before applying the requested interpolation process. This significantly speeds up many applications with no loss in accuracy. Zonation is recommended if the raw data has a large number of points. EFDC_Explorer informs the user of the range in number of data points in each zone before conducting the actual assignment.

For bathymetry and wave data the user has two choices for cell assignment, spatial interpolation via nearest neighbor or averaging data into each cell. If the XYZ data is very dense, relative to the model cell size, then the best approach will be to use cell averaging. However, if the XYZ data is not dense enough to completely assign at least one value for every applicable model cell, then the nearest neighbor interpolation option is better.

Pressing the Apply button causes EFDC_Explorer to perform the requested operations. You can perform a series of operations, one after the other by changing the options and pressing Apply. For example, you can set the water surface elevation from a data file with units in centimeters then change the Constant options and change the Operator to "/ 100" to convert the elevations to meters. Once assigning/editing the current parameter is complete, pressing the Done button returns to the main EFDC_Explorer form. The Done button does not do anything except return the user to the main EFDC_Explorer form.

Example Problem

The user has generated a poly line, and now wants to set a constant bottom elevation to all the cells inside the poly line.

1. Go to the Domain/Initial and Boundary Conditions tab.
2. Click on the Assign button for bathymetry. From the bathymetry assignment form, type in or browse to the polyline file.
3. Select the Flat Bottom option and enter the elevation in the text box
4. Click Apply. If the polyline is not closed, EE will ask you if you want to treat it as open or closed. Open polylines select cells along the line. Closed polylines select all the cells whose corners/centroids are inside the polygon, based on the Inside Cell Test options.
5. EE will build a list of the cells and apply the specified flat bottom to those cells and report how many cells were modified.

Set Initial Conditions – Water Column

This section contains methods to assist the user to assign the initial conditions for the water column parameters. The check boxes next to each parameter set the flags for EFDC to read and use these initial condition fields. When an Assign button is pressed for a parameter (e.g. Bathymetry), the Apply Cell Properties via Polygons form is displayed with appropriate options for that parameter (e.g. Figure 5 9). Depending on the options selected on the spatial assignment form, the IC's can be initialized or modified, in one or more operations. Each water layer must be specified or the user can select the Set for All Layers to assign vertically uniform ICs.

The Assign Value Using Vertical Profiles option on the Apply Cell Properties via Polygons form allows the user to specify a data file with vertical profiles (data format in Appendix B) of the water quality parameter being assigned. In this case, the XYZ File will be the file that contains the vertical profile data. When the Apply button is pressed, EFDC_Explorer interpolates this data onto the water column initial conditions horizontally and vertically (all active layers).

Initial Condition to Offsets

The Initial Condition Offset to WS Elevation frame contains an input box that allows the user to apply a global offset to the Water Surface elevation that will be applied during the initialization.

Roughness Options

Under Bottom Roughness, other than the standard additive and multiplicative factors that EFDC will apply to whatever z₀'s are input in the DXDY.INP file, EFDC_Explorer has several methods to set and/or modify the z₀'s that will be written in the DXDY file.

Floodplain Z₀'s and Channel z₀'s: If the model was constructed with channel and floodplain cell ID's (i.e. 5 for channels and 7 for the floodplain in the cell map file, i.e., CELL.INP) then the user can set each one quickly using these buttons.

Polygon Set: The user can employ a user defined polygon to modify/set the z₀'s. This tool may be applied as many times as needed anytime during the model construction and calibration process.

Legacy Options

EFDC_Explorer allows the user to make changes to older (legacy) models whose functions have been superseded by changes in the EFDC_Explorer/EFDC_DSI modeling system. It is not recommended users edit these fields unless the user wants to maintain consistency with some legacy model.