Calculator input
Enter your design wave conditions and slope information. The form uses a 3-column layout on large screens, 2 columns on smaller screens, and 1 column on mobile.
Example data table
These example rows show how different coastal slope and wave combinations can change the Iribarren number and the likely breaker response.
| Case | Wave Height (m) | Period (s) | Slope Input | L₀ (m) | ξ | Breaker Type |
|---|---|---|---|---|---|---|
| Rock revetment option A | 1.20 | 5.00 | 1V:2H | 39.03 | 2.85 | Plunging |
| Gentle armor slope | 2.80 | 8.00 | 1V:3H | 99.92 | 1.99 | Plunging |
| Steep coastal structure | 4.50 | 10.00 | 1V:1.5H | 156.13 | 3.93 | Surging / Collapsing |
Formula used
Iribarren number:
ξ = tan(α) / √(H / L₀)
Deep-water wavelength:
L₀ = gT² / (2π)
Wave steepness:
H / L₀
Where:
- ξ = Iribarren number or surf similarity parameter
- α = structure slope angle to the horizontal
- tan(α) = slope ratio used in the calculation
- H = wave height in meters
- L₀ = deep-water wavelength in meters
- T = wave period in seconds
- g = gravitational acceleration
In practical use, lower ξ values trend toward spilling waves, midrange values often align with plunging behavior, and higher values trend toward surging or collapsing conditions.
How to use this calculator
- Enter the design wave height in meters.
- Enter the representative wave period in seconds.
- Select how you want to describe the slope.
- Provide either V:H ratio, slope angle, or tan(α).
- Keep gravity at 9.81 m/s² unless you need another value.
- Add a case label to track alternatives during design review.
- Click the calculation button to show results above the form.
- Review ξ, wavelength, steepness, graph, and breaker classification.
- Use the CSV or PDF buttons to save the result summary.
Frequently asked questions
1) What does the Iribarren number measure?
It measures surf similarity by combining slope steepness and wave steepness. Engineers use it to compare how incoming waves may break or run up on beaches, revetments, breakwaters, and other sloped coastal structures.
2) Why is deep-water wavelength included?
Deep-water wavelength converts wave period into a length scale. That lets the calculator estimate wave steepness, which strongly affects surf similarity and the resulting Iribarren number.
3) Can I enter slope as a ratio?
Yes. You can enter slope as vertical and horizontal components, as an angle, or directly as tan(α). The calculator converts each option into a consistent slope term for the final equation.
4) What does a low ξ value usually imply?
A low value usually points toward spilling-type behavior. That generally means more gradual breaking and energy dissipation over the slope rather than a concentrated plunge near the face.
5) What does a high ξ value usually imply?
A higher value often suggests surging or collapsing conditions. Those cases can involve stronger run-up, less classic plunging, and a steeper interaction between the wave and structure.
6) Is this suitable for final design approval?
It is best for screening, concept comparison, and preliminary checks. Final design should still follow project-specific standards, physical model data, local wave climate studies, and professional engineering review.
7) Why does the graph vary wave height only?
It helps you see sensitivity quickly. Holding slope and period constant shows how changing wave height alone can shift the Iribarren number and move the design toward different breaker tendencies.
8) Can I use this for breakwaters and revetments?
Yes. It is especially useful for sloped coastal elements such as revetments, rubble structures, armor slopes, and breakwater faces when you need a quick surf similarity estimate.