Level Curves

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

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

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

The Level Curves dialog box contains the following areas:

Curve List

Displays the level curves available in the current drawing.

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

Level Curve Creation

Specify identifying information for the selected level curve.

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

Curve Data

Defines the level curve using time and level values.

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

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 level 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 level curve, based on the last time value in the table.
• Maximum level: The highest level value contained in the level curve.

To Create a Level Curve

1. Open the Level Curves dialog box.
2. In the Curve List, click +.
3. Enter a Name for the level curve.
4. Optionally, enter a Description.
5. Select a Curve continuation option.
6. Enter the time and level 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 level curves.

To Modify an Level Curve

1. Open the Level Curves dialog box.
2. Select an level 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 level curve.

To Delete an Level Curve

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

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