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Compare-Contrast-Connect: Estimating Wave Height

NGSS Science and Engineering Practices:

NGSS Crosscutting Concepts:

Whether you are a surfer, a boater, or a casual observer, being able to tell how big a wave is can be very important. There are two simple ways to estimate the height of the surf.


Method A

Judge the relative height of the waves as compared to a surfer, a boat in the water, or some other reference. For example, if a surfer appears as tall as your thumb and the surf appears twice as tall as your thumb, then the wave is about twice the surfer's height (SF Fig. 4.4).


<p><strong>SF Fig. 4.4.</strong> Depiction of a method for estimating wave height from a known object in the water</p><br />


Method B

If it is safe to do so, the size of the wave can be estimated by walking down the slope of a beach until the top of the breaking wave and the distant horizon are aligned. When the wave and horizon are aligned, the vertical distance from eye level to sea level, or the level of the water returning to the sea, is about the height of the wave (SF Fig. 4.5).

<p><strong>SF Fig. 4.5.</strong> Depiction of a method for estimating wave height by knowing your height above sea level</p><br />


Question Set: 
  1. If the surfer shown in SF Fig. 4.4 is 2.0 m tall, how high is the wave?
  2. If the girl shown in SF Fig. 4.5 is 1.5 m tall and is standing 0.5 m above sea level, how high is the wave?
  3. What are some of the safety precautions that
    1. spectator should keep in mind when observing waves from the shoreline?
    2. a surfer or body surfer should keep in mind when riding waves?

Special Feature Type:

Exploring Our Fluid Earth, a product of the Curriculum Research & Development Group (CRDG), College of Education. University of Hawaii, 2011. This document may be freely reproduced and distributed for non-profit educational purposes.