Gradually Varied Flow Calculator

Calculate water surface profiles using the Direct Step Method. Analyze backwater and drawdown curves with automatic profile classification (M1, M2, S1, etc.) for open channels.

Water Surface Profile Classifications

Mild Slope (yn > yc)

  • M1: Backwater (y > yn)
  • M2: Drawdown (yc < y < yn)
  • M3: Supercritical (y < yc)

Steep Slope (yn < yc)

  • S1: Backwater (y > yc)
  • S2: Drawdown (yn < y < yc)
  • S3: Backwater (y < yn)

Other Classifications

  • C1, C3: Critical slope
  • H2, H3: Horizontal bed
  • A2, A3: Adverse slope

Input Parameters

Flow Parameters

cfs

Roughness coefficient

Channel Geometry

ft
:1 (H:V)

0 for rectangular

ft/ft

Profile Computation

ft

Known depth at control section

ft

Target depth for computation

Computation increments

ft

Reference location

Velocity distribution correction (typically 1.0)

Ready to Calculate

Enter channel parameters and depth range to compute the water surface profile.

For educational purposes only. Not a substitute for professional engineering judgment.

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