Creating User-defined Shapes (SWMM)

A user-defined conduit shape is defined by a set of height-width relationships. Vertically symmetric cross sections for closed conduits can be defined using a shape curve while vertically symmetrical or asymmetric cross sections for open conduits are defined using transects.

The shape curve defines how the width of a cross section varies with depth for a conduit with a custom type of shape. These are both normalised with respect to full depth.

A transect defines how bottom elevation varies with horizontal distance over the cross section for a conduit with an irregular type of shape.

Specifying a user-defined shape curve

To define a new user-defined shape curve:

1. In the conduit property sheet, select the Custom option from the Shape dropdown list.

   The Shape curve field is now displayed.

2. Select the button located to the left of the Shape curve and select Insert New Shape Object option from the context menu.
3. Enter a name for the new shape curve and click OK. This displays the Shape curve property sheet with the name of the new curve displayed in the ID field.
4. Click , which is located to the right of the Geometry field, to display the Shape Curve Editor.
5. In the editor, specify a series of depths and corresponding widths for the cross section in the Depth/full depth and Width/full depth fields respectively. The specified values will appear in the 3d view, which represents how the width of the cross-section varies with height, where both width and height are scaled relative to the section's full depth.
6. Click OK when the shape curve has been defined.

Alternatively, a new shape can be added in the append row of the Shape Curve Grid Window of the Links Grid. Double click on the new shape to display the Shape curve property sheet.

Specifying a user-defined transect

To define a new user-defined transect:

1. In the conduit property sheet, select the Irregularoption from the Shape dropdown list.

   The Transect field is now displayed.

2. Click , which is located to the left of the Transect field, and select Insert New Transect Object option from the context menu.
3. Enter a name for the new transect and click OK. This displays the Transect property sheet with the new transect's name displayed in the ID field.
4. Click , which is located to the right of the Profile field, to display the Transect Editor.
5. In the editor, specify a series of Station and Elevation relationships for the transect. A station represents the distance from the left bank, so the first entry on the grid should represent the elevation at the start of the cross section on the left bank, and the last entry in the grid should represent the elevation at the end of the cross section on the right bank. The transect is illustrated in the editor as the relationships are entered.
6. Click OK when the transect has been defined.

Alternatively, a new transect can be added in the append row of the Transect Curve Grid Window of the Links Grid. Double-click on the new transect to display the Transect property sheet.