Re: [Paddlewise] Surfing in S. Cal. should be exciting...

Mark Perkins wrote:
>>>>>.....Short answer is "yes". It depends primarily on the period of the
swell and
also on the shape of the bottom converting the swell to surf. The longer the
period the higher the surf height / swell height ratio.<<<<<<<<<



Furthermore, the shape of the bottom farther out to sea interacts with the
swell when the ratios between water depth and swell length and height are
withing certain parameters. This can serve to bend the direction that the
local swell is taking. This can result in a swell being focused onto a small
area and a large increase in local swell height results. Most coastal paddlers
have probably noticed that the conditions are usually rougher near points of
land and are more mild in bays. The shallows (often offshore of the points of
land) bend the swells direction as the shallows slow the swell some focusing
more wave energy on the points of land. This same thing removes energy from
the swell entering a bay as the wave energy is spread out over a wider area.



Somewhere (possibly the last edition of Waves and Beaches by Willard
Bascom--out of print but a great read for coastal kayakers) I read about a
jetty (maybe in CA) that was destroyed in relatively mild swell because of the
(rare--maybe from the southern ocean) direction the relatively mild swell was
coming from interacted with the underwater topography offshore to focus the
energy from a wide area of sea onto a part of the jetty that was torn apart by
huge waves that were confined to only in a small area.
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