Calculator Inputs
Example Data Table
| H (m) | T (s) | d (m) | Computed L (m) | Steepness H/L | Rating |
|---|---|---|---|---|---|
| 1.2 | 6 | 10 | 48.39 | 0.0248 | Moderate |
| 2.5 | 8 | 15 | 81.77 | 0.0306 | Moderate |
| 0.8 | 4.5 | 5 | 26.3 | 0.0304 | Moderate |
Formula Used
Wave steepness is computed as S = H / L, where H is wave height and L is wavelength.
- Deep-water wavelength: L0 = gT² / (2π)
- Finite-depth wavelength: solve ω² = gk tanh(kd), where ω = 2π/T and L = 2π/k
- Celerity: C = L / T (useful for timing and exposure)
How to Use This Calculator
- Pick a unit system that matches your field notes.
- Enter wave height H and period T.
- Either provide wavelength L, or compute it.
- If computing nearshore, also enter depth d.
- Press Submit to view steepness, wavelength, and checks.
- Use CSV or PDF export for logs and reporting.
Tip: If you have measured wavelength from surveys or instruments, prefer the provided option to reduce model assumptions.
Technical Article
1) Why wave steepness matters on site
Wave steepness S=H/L is a compact indicator of wave shape that affects overtopping, armor stability, and construction windows. For the same height, shorter waves are steeper and usually more damaging to exposed temporary works. Many field teams log Hs and Tp; this calculator turns those into a consistent steepness check for daily reports.
2) Typical ranges seen in coastal projects
In moderate seas, steepness often falls between 0.01 and 0.05. Long-period swell can be gentle (S<0.02) even with notable height, while short-period wind waves can reach 0.06 or higher. Nearshore shoaling and depth limits can increase steepness as wavelength shortens.
3) Breaking tendency and quick screening data
A widely used deep-water screening guideline is that breaking becomes likely as H/L approaches about 1/7 ≈ 0.143. In practice, breaking can occur at lower values depending on current, depth, and spectral spreading. The result panel flags this guideline so supervisors can re-check exposure assumptions and stop-work criteria.
4) Wavelength estimation choices and what they mean
If you enter wavelength directly, the calculation is purely geometric. If you compute wavelength from the period, the calculator offers deep-water and finite-depth options. Deep-water L0=gT²/(2π) is fast and works best when d/L is large. Finite-depth dispersion solves ω²=gk tanh(kd) to improve accuracy for nearshore works such as revetments, jetties, and cofferdams.
5) Relative depth (d/L) as an operational indicator
Relative depth is reported as d/L. Values below about 0.05 indicate shallow-water behavior where wavelength depends strongly on depth; values above about 0.5 behave closer to deep water. Use this data point to justify when a finite-depth model is necessary for the day’s conditions.
6) Construction uses: stability, access, and planning
Steeper waves tend to increase instantaneous pressures and can reduce safe access time on barges and temporary trestles. When coordinating armor placement, steepness helps interpret whether the sea state is dominated by short wind waves or longer swell, guiding decisions on lift sequencing, mooring adjustments, and equipment demobilization timing.
7) Data quality tips for consistent results
Record the measurement source (buoy, radar, visual estimate) and whether height represents significant or maximum wave height. Pair heights with the correct period definition (Tp peak period vs. Tz zero-crossing). If depth varies with tide, log the water level or the effective depth at the structure toe.
8) Reporting and audit trail with exports
CSV export supports daily logs and spreadsheet checks, while the PDF report is suitable for method statements, inspection packs, and shift handover notes. Include the optional site note to preserve context such as “north breakwater toe” and “mid-tide conditions.” Maintaining these data points improves traceability when reviewing delays, damage, or change events.
FAQs
1) What does wave steepness represent?
It is the ratio H/L. Higher values mean a more “peaked” wave shape, often linked with stronger impacts, more runup variability, and increased breaking likelihood.
2) Should I use the provided wavelength or compute it?
If you have measured wavelength from surveys or instruments, use it. Otherwise compute wavelength from period and depth for a consistent estimate, especially for routine reporting.
3) When is finite-depth dispersion recommended?
Use it when the project is nearshore and depth is known. It improves wavelength where d/L is small and deep-water assumptions can overestimate wavelength.
4) What is a common breaking guideline shown here?
The calculator flags the deep-water screening guideline near H/L ≈ 1/7. Breaking can still occur below that value depending on depth, currents, and wave spectrum.
5) Why does the result include celerity?
Celerity C=L/T helps estimate wave arrival timing and supports exposure planning. It is also useful when checking instrument plausibility and nearshore transformation trends.
6) My steepness looks unusually high—what should I check?
Confirm units, height definition (Hs vs. maximum), and period type. If depth is omitted, computed wavelength may be too long or short for the location.
7) Can I use this for final design approval?
Use it for screening and documentation. Final design should follow the project’s governing standards, site-specific metocean data, and a qualified engineer’s review.