Calculator Inputs
Example Data Table
| Scenario | Slope (V/H) | H₀ (m) | T (s) | Multiplier | ξ (typical) | Breaker |
|---|---|---|---|---|---|---|
| Gentle revetment | 0.33 | 1.2 | 8 | 1.00 | ~0.60 | Plunging |
| Standard rock slope | 0.50 | 2.0 | 10 | 1.10 | ~1.26 | Plunging |
| Steep face | 0.80 | 1.5 | 6 | 1.00 | ~2.32 | Plunging |
| Very steep wall | 1.20 | 1.0 | 5 | 1.00 | ~4.04 | Surging |
Values are illustrative; site spectra and depths change outcomes.
Formula Used
Deep-water wavelength: L0 = g T² / (2π)
Deep-water steepness: S = H / L0
Iribarren number: ξ = tan(α) / √(H / L0)
Here H is the design height after applying the multiplier. The effective slope factor scales tan(α) to reflect composites.
How to Use This Calculator
- Select units and confirm gravity if needed.
- Enter deep-water wave height H₀ and wave period T.
- Choose slope input: ratio (V/H) or angle in degrees.
- Apply a height multiplier for conservative checks.
- Optionally adjust effective slope for berms or roughness.
- Press Calculate to view ξ, wavelength, steepness, and breaker type.
- Download CSV or PDF for project records.
Breaker Interpretation Guide
Professional Notes on the Iribarren Number
1) Why the Iribarren number matters
The Iribarren number (ξ) links offshore wave steepness to slope steepness, providing an indicator of how waves will break on a structure or beach. Designers use it to anticipate impact, runup style, and reflection, which influence revetment stability and overtopping risk.
2) Typical input ranges in practice
For preliminary checks, deep-water significant wave height commonly falls between 0.5–6.0 m, while peak periods range 4–16 s. Revetment faces are frequently 1V:1.5H to 1V:3H (tanα ≈ 0.67 to 0.33). Adjust these ranges to local wave climate and bathymetry.
3) Deep-water wavelength and steepness
The calculator uses the linear deep-water wavelength L0 = gT²/(2π). Combining L0 with the selected design wave height gives steepness S = H/L0. Typical deep-water steepness values of 0.01–0.06 are common; values above this suggest short periods, large waves, or inconsistent inputs.
4) Representing slope correctly
Slope can be entered as V/H, which equals tanα, or as an angle measured from the horizontal. Many drawings report slopes as 1V:nH; convert to V/H as 1/n. The effective slope factor is a practical adjustment for berms, roughness, or composite faces.
5) Breaker regimes and thresholds
While project criteria vary, a practical guide is: spilling for ξ<0.5, plunging for 0.5≤ξ<3.3, and surging for 3.3≤ξ<5.0, with very high ξ trending to collapsing/surging behavior. Use these bands consistently across alternatives to compare breaker character.
6) What ξ implies for revetments
Lower ξ tends to spread dissipation over a wider zone, often reducing localized impact but increasing sustained turbulence. Mid-range ξ can create plunging loads and impulsive pressures. Higher ξ indicates runup-dominated action with stronger reflection, which can drive toe scour and demands careful tie-ins and filter design.
7) Sensitivity and QA checks
Because L0 scales with T², period selection can change ξ substantially. A 20% increase in T raises L0 by 44%, lowering steepness and increasing ξ. Review the “Checks & notes” messages, confirm unit selection, and document whether H represents Hs, Hm0, or another definition.
8) Reporting with exports
Use the CSV for traceable spreadsheets and the PDF for submittals. Record the source of wave statistics, the slope basis, and any multiplier rationale. Pair ξ with project-specific runup and overtopping methods for final design. Documented assumptions improve peer review and reduce rework later. Always keep versioned inputs with dates for transparency.
FAQs
What does the Iribarren number represent?
It relates slope steepness to offshore wave steepness, indicating expected breaker behavior on a sloping face. It supports quick comparisons of alternatives and helps anticipate runup style, reflection, and likely load character.
Which wave height should I enter?
Use the deep-water design height consistent with your criteria, commonly significant height. If you apply a multiplier, document why, and keep the same definition across options to avoid mixing statistics.
What slope value should I use for a 1V:2H face?
Enter V/H as 1/2 = 0.5, or enter the equivalent angle of about 26.6 degrees. Use the as-built or design cross section at the location that controls stability.
Why does period affect results so much?
Deep-water wavelength scales with T², so small period changes move steepness and ξ noticeably. Confirm the period type (peak, mean, or spectral) and use values from the same wave dataset.
How should I interpret the breaker type labels?
They are typical bands used for engineering screening. Use them to understand relative behavior, not as a substitute for detailed runup, overtopping, or physical modeling when required.
Can I use this for composite slopes and bermed revetments?
Yes, as a screening tool. Represent the controlling face using V/H or angle, then adjust the effective slope factor to reflect berm influence or roughness. Record the assumption and check sensitivity.
Are the CSV and PDF exports suitable for submittals?
They summarize inputs and computed metrics for traceability. For formal submissions, add wave-statistics source, project location, water level assumptions, and the design standard or method you used alongside ξ.
Use this tool to classify breakers and design safely.