Re: [Paddlewise] Breaking Waves Issue?

> I recently purchased and have been enjoying reading Sea Kayaker Magazine's
> Handbook of Safety and Rescue by Doug Alderson and Michael Pardy. However,
> something seemed unusual on page 48 as I read, "The crest will rise and
> break when the depth of the water is approximately three-quarters of the
> swell height. A 4-foot swell will break in water 3 feet deep. The height of
> the wave at the time it breaks will be approximately 1.5 times its original
> deep-water height. The 4-foot swell will rise to a 6-foot crest before
> breaking in 3 feet of water."


   I tried to send this off yesterday morning but I guess the e-mail got lost
in limbo. So let's try this again, shall we?

   I don't have the book so I can't verify what it says. However, what it
should read is that a wave will break when the depth of the water is
approximately four-thirds it's own height (actually when the depth of the
water becomes
less then 1.28 times the wave height), or the waves steepness surpasses 1/7
(the
wave height cannot be greater then one seventh of the wave length). Your
4-foot wave would actually break in about 5.3 feet of water, a 3-foot wave
will
break in about 4-feet of water and a 6-foot wave will break in about 8-feet of
water.
   That said I usually use 1.5 when I am discussing this in my classes. It's
easier for people to do the numbers in their head while sitting on the beach
early in the morning and I feel it is plenty close enough for our purposes.

Scott
So.Cal.
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