Tsunami Speed & Arrival Time Calculator (Shallow Water c=√(gh))

Calculate approximate tsunami wave speed and arrival time from average water depth and distance (for learning).

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Example Presets

Selecting a preset fills the inputs and immediately updates the results and graphs.

Inputs

Advanced Settings

Results

Wave Speed (km/h)
Arrival Time (hh:mm:ss)
Wave Speed (m/s)
Arrival Time (sec)
Arrival Time (hours)

Graphs

Depth → Wave Speed (c=√(gh))

Distance → Arrival Time (Mode A)

Assumptions and Cautions

Formula used

Using the shallow-water wave approximation, wave speed is c = √(g h) and arrival time is t = d / c.

Where h is the average water depth (m), d is distance (m), and g is gravity (m/s²).

Prerequisites and Limitations
  • Assumes constant average water depth.
  • Does not consider refraction/reflection due to seafloor topography, or coastal shallow-water deformation/run-up.
  • Actual tsunami arrival times can vary significantly from these estimates.
FAQ
  • Why is it faster in deeper water? In the shallow-water approximation, wave speed is proportional to √h. Tsunamis commonly satisfy λ≫h (rule of thumb: λ>20h), so this approximation is often used.
  • How is average depth determined? Since real ocean depth varies, strictly speaking, interval division is necessary.
  • Can it be used for disaster prevention? No. This tool is for educational use. Please always refer to official government information.

How to use this calculator effectively

This guide helps you use Tsunami Speed & Arrival Time Calculator (Shallow Water c=√(gh)) in a repeatable way: define a baseline, change one variable at a time, and explain each output using explicit assumptions before sharing results.

How it works

The calculator applies deterministic formulas to your input values and only rounds at the final display layer. This makes it useful for comparative analysis: keep one scenario as a baseline, then vary assumptions and measure the delta in both absolute terms and percentage terms. If a change appears too large or too small, verify units, period conventions, and sign direction before interpreting the result.

When to use

Use this page when you need a fast planning estimate, a classroom check, or a reproducible scenario that teammates can review. It is most effective at the decision-prep stage, where you need to compare options quickly and decide which assumptions deserve deeper modeling or external validation.

Common mistakes to avoid

Interpretation and worked example

Start with a baseline case and save that output. Next, edit one assumption to reflect your realistic alternative, then compare both the direction and size of change. If the direction matches domain intuition and magnitude is plausible, your setup is likely coherent. If not, check hidden defaults, unit conversions, boundary conditions, and date logic before drawing conclusions.

See also

FAQ

What should I enter first?

Start with the minimum required inputs shown above the calculate button, then keep optional settings at their defaults for a first pass. After getting a baseline, change one parameter at a time so you can explain which assumption moved the output.

How precise are the results?

The calculator keeps internal precision and rounds only for display. Small differences can still appear if another tool uses different constants, period conventions, or rounding rules. Align assumptions before comparing final values.

Why can my result differ from another calculator?

Many tools choose different defaults for units, rate basis, date-count logic, and sign conventions. Verify those defaults first. If differences remain, use the worked example and compare each intermediate step to locate the branch that diverges.

Can I use this output for official decisions?

Use this page for educational planning and quick checks. For legal, medical, tax, or regulated decisions, confirm your result with official guidance or a qualified professional because institutional rules may include extra constraints.

Does this page send my inputs to a server?

Core calculations run in your browser. Some share links encode parameters in the URL so results can be reproduced, but no hidden upload is triggered unless you explicitly share that URL.

How to use Tsunami Speed & Arrival Time Calculator (Shallow Water c=√(gh)) effectively

What this calculator does

This page is for estimating outcomes by changing inputs in one controlled workflow. The model keeps your focus on variables, not output shape. Start with stable assumptions, then test sensitivity by changing one key input at a time to observe directional impact.

Input meaning and unit policy

Each input has an expected unit and a typical range. For reliable interpretation, check whether you are using the same unit system, period, and base assumptions across all runs. Unit mismatch is the most common source of unexpected drift in numeric results.

Use-case sequence

A practical sequence is: first run with defaults, then create a baseline log, then run one alternative scenario, and finally compare only the changed output metric. This sequence reduces cognitive load and prevents false pattern recognition in early experiments.

Common mistakes to avoid

Avoid changing too many variables at once, mixing incompatible data sources, and interpreting a one-time output without checking robustness. A single contradictory input can flip conclusions, so keep each experiment minimal and document assumptions as part of your note.

Interpretation guidance

Review both magnitude and direction. Direction tells you whether a strategy moves outcomes in the desired direction, while magnitude helps you judge practicality. If both agree, you can proceed; if not, rebuild the baseline and verify constraints before deciding.

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