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Green’s Law Wave Shoaling & Amplitude Calculator

Green’s Law describes the shoaling of long gravity waves traveling into gradually shoaling water and converging channel widths.

Deep-water or initial wave height.

Initial water depth.

Shallow coastal water depth.

Initial width of channel or bay.

Constricted coastal width.

Calculated Result
1.778 m

Shoaled Wave Height (H₂)

Shoaling Amplification Factor

1.778×

Initial Wave Celerity (c₁)

22.14 m/s

Shoaled Wave Celerity (c₂)

7.00 m/s

Calculation Breakdown

  1. Green’s Law FormulationH2 = H1 * (b1/b2)^0.5 * (h1/h2)^0.25 = 1 * 1.778 = 1.778 m

What Is the Green’s Law Wave Shoaling & Amplitude Calculator?

Green’s Law describes the energy conservation of non-breaking long waves in slowly varying shallow channels.

How Does the Green’s Law Wave Shoaling & Amplitude Calculator Work?

As water depth decreases, wave propagation celerity c = sqrt(g*h) slows down, compressing wave energy into greater height.

Green’s Law Wave Shoaling & Amplitude Calculator Formula & Variables

The core mathematical equation utilized by this calculator is expressed as:

H_2 = H_1 \left( \frac{b_1}{b_2} \right)^{1/2} \left( \frac{h_1}{h_2} \right)^{1/4}, \quad c = \sqrt{g h}

Green’s law for long wave amplitude shoaling and shallow water wave celerity.

How to Use the Green’s Law Wave Shoaling & Amplitude Calculator

  1. Input initial wave height, initial and shallow water depths, and channel widths.

Step-by-Step Example Calculation

Tsunami Coastal Shoaling

Input Values:

initialWaveHeightMeters:1
initialWaterDepthMeters:50
shoaledWaterDepthMeters:5
initialChannelWidthMeters:1
shoaledChannelWidthMeters:1
Worked Steps: Predicts shoaling amplification factor of 1.778× and shoaled wave height of 1.78 m.

Understanding Your Result

Reveals shoaled wave height, amplification factor, and wave speeds.

Factors That Affect the Result

  • Channel funneling (b1 > b2) compounds with depth reduction to create extreme wave run-up heights.

When Should You Use This Calculator?

  • Tsunami inundation hazard forecasting, tidal bore modeling, and harbor basin resonance analysis.

Assumptions & Limitations

  • Assumes long shallow water waves (wavelength L >> depth h) with negligible bottom friction and no wave breaking.

Frequently Asked Questions

Calculation Accuracy & Reference Note

Classical hydrodynamics formulation first derived by George Green in 1837.

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