Grid Masks

General Purpose

Masks are thin dams that may be configured on a cell face in order to fully or partially block flow between cells in the model domain. This feature is accessed from the 2DH View, where a Grid Mask layer appears in the Layer Control frame by default.

Fully Blocking: Fully blocking mask means that it blocks completely the movement of water from the top to the bottom of the water column.

Partially Blocking: Partially blocking mask means that it blocks partly the movement of water of the water column. Masks can be fixed in place so that only water can only flow through certain cells in the vertical and horizontal despite change in water levels. Alternatively, the masks can be on a floating object, so that water can still move under the mask. and this changes depending on water level e.g. a floating bridge. Figure 1 provides a schematic of the components of a partially blocking mask.

Figure 1. Mask Schematic Diagram.

Anchor Elevation: In EE if it is set to 0 the object on the water will be considered as floating (e.g ships), otherwise it is a fixed object (e.g bridges, docks).

Draft: It is thickness of the floating or fixed object on water.

Clearance: it is thickness of space between the Draft and Bottom Sill, when it is equal to 0, the object plays a role of fully blocking mask, otherwise it is partial blocking mask.

Bottom Sill: It is thickness of a solid structure on the surface of riverbed.

Bottom: it means riverbed.

2DH View

Adding New Masks to Grid Cells

Masks can be added from the 2DH View, where the Masks layer is displayed on the Layer Control as default. To add the masks, select the Masks layer then turn on the light bulb, pointer and pen icons as shown in Figure 1. Masks can be assigned to a single grid cell or multiple cells.

Add masks to single cell: When the editing model is enable, LMC on a cell to select the cell, then RMC on that cell. Four options will be displayed as shown in Figure 2.

  • Add Both West & South Completely Blocking Masks: Add a mask on both south and west faces of the selected cell.
  • Add Completely Blocking South Mask: Add a mask on the south face of the selected cell.
  • Add Completely Blocking West Mask: Add a mask on the west face of the selected cell.
  • Edit Cell Blocking Mask: After selecting this option the Vertical Cell Face Blocking form appears as shown in Figure 3. The cell ID (L, I, J indices) will be added to the List of Cells frame. The cell indices and initial condition are displayed on the Current Cell frame. By selecting this option, EE understands that the user wants to add a partially blocking mask (floating or fixed object) to the selected cell so the checkbox Floating is checked as default. In addition, the Anchor Elevation box is greyed out so it is non-editable. The user can now enter values for the Draft and Bottom Sill. When the Floating checkbox is unchecked then the Anchor Elevation box can edited. If the value entered is non-0 the mask now is partially blocking as a fixed object.

The Edit Cell Blocking Mask option can  also be used to edit the existing cells with assigned masks. These cells are in the List of Cells frame. LMC on a cell from this list then change properties of mask on the right frame. To add a new cell with masks enter the I, J, L index in the Indices then press Enter key or click the  button. To remove a cell from the cell list, LMC on that cell then click the   button. Click button to remove all cells at once as shown in Figure 3.

Figure 1. Turn on Light of Masks layer.

Figure 2. Add Masks to Grid Cells.

Figure 3. Vertical Cell Face Blocking.

Add masks to multiple cell: To add masks to multiple grid cells at the same time. the multiple cells must be selected first. Holding the Ctrl key and LMC to select different single cell or holding Shift key and LMC to select a range of contacting cells. Otherwise how to select grid cell is described in Grid Cell Selection. The next steps to add masks to these cells are similar to adding mask to single cell presented above.

GUI Editing

LMC on the Mask layer in the Layer Control to have some following options as shown in Figure 4.

  • Properties: Set properties for display of the masks such as style, color. After selecting this, the Mask Properties form appears as shown in Figure 5. From this form the user can set a new name for Layer Name. Check the box for Layer Visible will allow the grid mask display to be toggled in the 2DH View. Check the box of Show in Legend will allow legend of the grid mask to be displayed in the Legend in the 2DH View. Checking this box is only applied when when the Layer Visible option is checked. Settings for styles and color of masks are also applied from this form.
  • Edit: When this option is selected, 2DH View Option form appears as shown in Figure 6. From this form, the user can change the Mask layer to other layer in the Layer Control by changing the Primary Group and Parameter.
  • Edit Cell Blocking Mask: Edit cells which have masks. When this option is selected, Vertical Cell Face Blocking form appears as shown in Figure 7. How to use this form is described in detail below.
  • Zoom to Layer: Zoom to grid cells which have masks.
  • Remove: Remove the Mask layer from the Layer Control frame.

Figure 4. RMC options for Grid Mask layer.

Figure 5. Mask Properties settings form.

Figure 6. Edit option.

Figure 7. Edit Cell Blocking Masks (1).

On the Vertical Cell Face Blocking form as shown in Figure 7, it shows all the grid cells of the domain which having masks of the domain on the List of Cells frame. I, J, L indices of the cell are shown in the Cell Indices frame. Initial conditions of the cell including bottom elevation, water depth, water surface elevation are shown in the Initial Conditions frame, these fields are not editable. The user can edit the cell's mask by changing mask's properties on the Current Cell frame.  In this case, the cell (L=97) has masks on the west and south faces so boxes for Completely Block Mask of the two faces are checked (see Figure 7)

In case the user wants to change a mask from completely blocking to partially blocking, the box needs to be unchecked. For example we will uncheck the box for the west face. Then the Floating option can be checked or unchecked, values for Draft, Bottom Sill can be entered as shown in Figure 8. Click the Close button to complete setting the masks for the grid cell.

From the 2DH View, the user also remove masks by RMC on cell which contains masks on the west or south faces then select  "Delete" option as shown in Figure 9.

Figure 8. Edit Cell Blocking Masks (2).

Figure 9. Remove grid masks.

EFDC+ Input File

The EFDC input file for masks is mask.inp, in the file will show the number of cells having masks with three columns including I, J and MTYPE colums. In which MTYPE column is type of mask configured to grid cell. (see Figure 10)

Figure 10. EFDC input file for mask.