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.
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