Hydraulic Jump
Sequent depth, energy loss and jump length from the supercritical depth, by momentum and FHWA HEC-14.
Results
Enter your values; the answer appears here as you type.
- Sequent depth
- Q2/(g A1) + A1 Y1 = Q2/(g A2) + A2 Y2 (HEC-14 Eq. 6.1), solved for the depth above critical. In a rectangle this equals y2 = (y1/2)((1 + 8 Fr2)1/2 − 1).
- Length
- For a rectangle, L = 220 y1 tanh((Fr − 1)/22) (HEC-14 Eq. 7.25). HEC-14 prints no length equation for other sections, so none is given.
- Form
- The Froude number ranges of HEC-14 Chapter 6: below 1.7 slight disturbance, then prejump, oscillating, stable, and above 9 efficient with a rough surface.
The calculator is tested against the cases below every time its code changes.
| Case | What | Reference | Values compared | Largest difference | Result |
|---|---|---|---|---|---|
| The table loads with the calculator. The same results are in verification.json. | |||||
Rectangles against the Belanger equation and trapezoids against a separate solution of the momentum function. HEC-14’s example reads its ratios from charts at a rounded Froude number, so it allows 6%.
- A horizontal or nearly horizontal channel: HEC-14 treats slopes up to 18 percent as horizontal. Sloped-channel jumps and pipes are not computed.
- The page finds the depth a jump needs, not whether it forms or where. That depends on the tailwater; compare it with y2.
- No stilling basin design. See the Riprap Apron & Basin calculator for riprap protection.
- Where do I get the depth before the jump?
- The supercritical depth arriving at the jump: for example the outlet depth from the Culvert calculator or the depth from the GVF Profile calculator.
- Can I attach the calculation sheet to a report?
- You can print it and include it as a supporting calculation that you have checked. It is a calculation aid, not a sealed engineering document: the engineer of record reviews and is responsible for what goes into a report.
| Topic | Reference |
|---|---|
| Method | FHWA (2006). Hydraulic Design of Energy Dissipators for Culverts and Channels, HEC-14, 3rd ed., FHWA-NHI-06-086, Chapters 6 and 7. |
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A free calculation aid using the published methods above. Not a sealed engineering document; the engineer of record is responsible for design. HERO E&C · TBPELS Firm F-27793.
Full disclaimer
A free calculation aid. This calculator applies the published methods named on this page to the inputs you enter. It is not a sealed engineering document, has not been reviewed by a licensed professional for your project, and no warranty is expressed or implied. Check the results independently before using them for design, bidding or permitting.
The criteria of the reviewing agency decide which methods and values apply to a design. The engineer of record is responsible for the design.
Using this calculator does not create an engineer–client relationship. Calculations run in your browser; your inputs are not sent to or stored by HERO E&C. HERO E&C · TBPELS Firm F-27793.