1D Embedded Structures Editor

For information about using the '1D Embedded Structures Editor', please refer to the section on How to embed a 1D structure in a 2D model

Technical details about the '1D Embedded Structures Editor' are given below.

The 'Select Structure Type' window allows you to select one feature and associate structure data.

Adding a culvert

Culvert – select a culvert shape type, default is rectangular, but any of the shapes offered for 1D river networks can be selected in the dropdown list. In addition, there is the option to include the effects of a single bend in the culvert, i.e. additional energy losses will be calculated (tick box to include a bend).

Adding an orifice

Orifice – there are no additional options to select with this structure type.

Adding a weir

Weir – select a weir type, default is general, but any of the types offered for 1D river networks can be selected in the dropdown list.

Note: If you access the structure type pop-up window for an already fully defined 1D structure, the window settings still always default to show a rectangular culvert selection (with no bend). Thus, press the 'Cancel' button to close the pop-up window without applying any changes.

After specifying a structure type for a polyline, the 1D structure editor table will show some fields automatically populated. Some of these fields can be edited directly within the table.

Show me what I can edit in the table

Parameters automatically filled are 'Node1', 'Node2', 'Structure Type' and 'Sub Type'. The node labels are always fixed for embedded structures and so are locked for editing. 'Structure Type' and 'Sub Type' can only be changed via the 'Structure Type' pop-up window. However, the following fields in the table can be edited directly within the table:

• Name - you can specify a unique name for each structure by clicking on the 'Name' field and typing as required (this is an optional setting).

• Length – the length value can override particular properties for each structure type:

  • For culverts it represents reach length. The default value is zero, which instructs the solver to use the length of the drawn line. A non-zero (positive) value overrides the length of the drawn line. Note: The line on map defines the 2D cells that interact with the start and end of a culvert.

  • For weirs it represents the breadth of weir. If set to a positive, non-zero value then this will override the breadth entered in the unit property window. Note: The direction of the line drawn on the map for a weir defines the orientation of the weir crest, i.e. flow will be considered perpendicular to the drawn line.

  • For orifices the entered length represents the orifice width. It is used to calculate bore area, overriding the bore area entered in the unit property window. Note: The start and end of the line on the map defines the 2D cells that calculated orifice flows are passed between.

• Include bend – setting applies only to culverts. Tick box to include additional energy loss due to single bend in culvert reach (this can also be set in the structure type pop-up window)

• Invert drop – setting applies only to culverts. This is the change in invert level between upstream and downstream conduit sections. Although the cross-section shape is always assumed constant in the conduit, you should specify a change in elevation to create a bed slope (to ensure water can flow through the culvert).

  Note: If you try to exit this tool without setting an invert drop a warning will be displayed informing you that invert drop is set to zero (you can still proceed to close and save if zero is the desired value).

• Distribution factor – setting determines how many 2D grid cells to distribute the outflow from the 1D structure across. This factor can only be 1, 2 or 3. The default factor is 1, which puts the entire outflow into the single 2D cell underlying the end of the structure line. In most cases this setting will be sufficient to achieve a stable model. However, if a model is showing an instability in the vicinity of an embedded structure, then distributing structure outflows over an increased area might help. If the factor is set to 2 then the outflow will be distributed across the same 2D cell and the immediately adjacent cells on either side (i.e. 3 cells in total). If the factor is set to 3 then the outflow will be distributed between all cells surrounding the cell underlying the end of the structure line (i.e. 9 cells in total).

  Note: This factor applies to culverts and orifices, but not weirs. Also, outflows will only be distributed across cells that lie within the 2D active area.

Note: The Edit 1D Structure tool can be used to review the properties defined for existing embedded structure shapefiles. As you need to put your shapefile in edit mode to access this functionality, it is also possible to edit your structure further in the tool. Remember that if you close the tool by clicking the OK button any edits will be saved automatically in the .str file.

What if I already have a shapefile to represent my structure?

If you already have a polyline shapefile drawn and want to use this to represent an embedded structure in a 2D model, then there are two options:

• Start a new 1D structure polyline (see point 1 in the previous sequence). Then, in the Layer Editor ribbon, activate the snapping tool and choose to snap to any point in your existing polyline.

  

• Edit the attributes of the existing shapefile, adding a field called “Type” that should be a text format.

To edit shapefile attributes in Flood Modeller, after loading the file into the Layers Panel (and map view) right-click on it and select Start Edit from the displayed menu. This will activate the Layer Editor ribbon in the main Toolbar. Then click on the “Attribute Window” button. The attributes table will be displayed in a pop-up window, which includes a toolbar.

Click the attribute editor button (as shown above). The editor appears in a new window that lists the current attribute fields and provides controls for adding new fields:

The above method should then be repeated to add another three text fields entitled “node1” and “node2”. These will hold the 1D node labels used in your embedded structures in the associated 1D structure file (as setup using the 1D structure tool). Culverts require both an inlet node label (node1) and outlet node label (node2) to be referenced. Weir and orifice type structures only require one label to be specified (node1, with node2 left blank). These data are used by the 2D solver to match the correct polyline with the relevant data in the associated 1D structure file.

Finally repeat the process again to add a numeric field that is type; double and entitled “length”. Values entered in this field represent culvert reach length, weir breadth or orifice diameter. The default entry should be 0.00, which tells the 2D solver to use the equivalent length parameter specified in the associated structure file.

The new fields will now be displayed when you return to the attribute table. While in edit mode, you can type directly into the table. The text entered in the Type field should only be one of the following; “culvert”, “weir” or “orifice”. The “str file” field can be left blank as Flood Modeller will populate this when you setup your embedded structure in the 1D structure tool.

After entering the required data, you can close the attribute window and click Save and then Stop Edit in the Layer Editor toolbar ribbon to apply your changes.

Note: Editing of the attribute table is only possible when a shapefile is in edit mode. If you access the attribute table just by right-clicking on the file in the Layers Panel, then the table is read-only (the editing options are disabled).