Elevation Curves

Use the Elevation Curves dialog box to create and manage elevation curves that define how water surface elevation varies over time.

Elevation curves are used to model tailwater conditions that fluctuate as a result of stormwater runoff, downstream system response, or tidal influences.

Elevation curves can be assigned to pipe network structures that are set to the outfall structure type, and use the elevation curve tailwater condition. During analysis, the specified elevation is applied as the tailwater condition based on the elapsed simulation time.

The Elevation Curves dialog box contains the following areas:

Curve List

Displays the elevation curves available in the current drawing.

• Select a curve to view or edit its properties.
• Click + to create a new elevation curve.
• Select the delete curve icon to delete it.

Elevation Curve Creation

Specify identifying information for the selected elevation curve.

• Name: Specifies the name of the elevation curve.
• Description: Provides an optional description of the elevation curve.

Curve Data

Defines the elevation curve using time and elevation values.

• Curve continuation: Specifies how the elevation curve is extended when the analysis runtime exceeds the duration of the curve.
  • Extend last elevation: Uses the final elevation value for the remainder of the analysis.
  • Repeat curve: Repeats the entire elevation curve until the analysis is complete.

The table contains the following columns:

• Time: The elapsed time from the beginning of the analysis. Values are entered in minutes and must increase sequentially.
• Elevation: The water surface elevation at the specified time. Values are displayed using the current drawing units (feet or meters).

Use the icons above the table to:

• Add a new row.
• Delete the selected row.
• Insert a row above the selected row.
• Insert a row below the selected row.
• Import curve data from a .csv file (if available).

Note: The first time value should be 0 (minutes) to define the starting elevation at the beginning of the analysis.

Graph

Displays a graphical representation of the elevation curve. The graph updates automatically as values in the table are modified.

Use the graph controls to zoom in, zoom out, reset the zoom, or expand the graph.

Summary

The following read-only values are calculated automatically:

• Duration: The total duration of the elevation curve, based on the last time value in the table.
• Maximum Elevation: The highest elevation value contained in the elevation curve.

To Create an Elevation Curve

1. Open the Elevation Curves dialog box.
2. In the Curve List, click +.
3. Enter a Name for the elevation curve.
4. Optionally, enter a Description.
5. Select a Curve continuation option.
6. Enter the time and elevation values that define the curve.
7. Use the icons to add or insert additional rows as needed.
8. Verify the curve using the graph.
9. Click Save Changes.

The new elevation curve becomes available for assignment to outfall structures that support tailwater elevation curves.

To Modify an Elevation Curve

1. Open the Elevation Curves dialog box.
2. Select an elevation curve from the Curve List.
3. Modify the curve name, description, continuation method, or curve data as required.
4. Review the graph to confirm the updated curve.
5. Click Save Changes.

Changes are applied to any structures that reference the elevation curve.

To Delete an Elevation Curve

1. Open the Elevation Curves dialog box.
2. In the Curve List, select or hover over the elevation curve to delete.
3. Select the Delete Curve icon.
4. Confirm the deletion when prompted.

Note: Deleting an elevation curve will remove it from all outfalls that reference it.