Manning Virtual Stream

The Manning formula calculates open flow in pipes and channels based on the Level measurement. While less accurate than hydraulic structures (e.g., flumes or weirs), it can provide sufficient accuracy in specific applications.

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Best Practices for Manning Formula Application

To ensure optimal accuracy, the following physical conditions are recommended:

• The channel should be straight for at least 200 feet (preferably 1,000 feet).

• The channel must have a uniform cross-section, slope, and roughness.

• Avoid rapids, dips, sudden contractions/expansions, or tributary flows.

• The flow must not be backed up or submerged.

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Steps to Configure a Manning Virtual Stream

1. Select the Level Stream

• Navigate to the Sites Tree.

• Select the device and the LEVEL stream to be used for the Manning virtual stream.

• Note the units of measurement used in the parent stream.

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2. Create the Virtual Stream

• In the right pane, go to the Configuration & Threshold tab.

• Click Create a Virtual Stream.

• In the Create Transformation window:

  • Select Manning as the type.

  • Click Submit.

• Refresh the browser to see the new virtual stream.

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3. Open the Manning Formula Editor

• In the Sites Tree, click the newly created stream.

• Open the Configuration & Threshold tab.

• In the Convert to Engineering Units section, click the pencil icon next to Click to initialize.

• The Edit Manning Formula window will open.

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4. Set the Formula Parameters

Ensure all units match the parent Level stream.

Channel Shape

• Select either Rectangular or Circular.

• Provide:

  • Channel Radius if shape is Circular.

  • Channel Width if shape is Rectangular.

Channel Slope

• Enter slope as a whole number.

  • Example: Type 1 for 1% (not 0.01 or 1%).

Manning’s Roughness Coefficient

Select a coefficient based on material and conditions. Consider:

• Surface roughness

• Vegetation

• Silting/scouring

• Obstructions

• Seasonal changes

• Channel shape and size

• Depth of flow (stage)

• Suspended material and bed load

Refer to manufacturer documentation for guidance.

Conversion Factor

Choose units matching the parent stream:

• SI Units (metric)

• English Units (inches, feet, yards)

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5. Submit the Configuration

• Click Submit to save all changes and activate the Manning virtual stream.

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Done!

Your Manning virtual stream should now be correctly configured and ready for data transformation based on flow calculations.