This weekend I heard a short piece on National Public Radio
that was discussing modification and exploitation
of coastal areas by pre-historic man. It was a sort of a
promo for a Science Magazine article. The particular thing
that caught my attention was: stone walls that collected
sand and allowed clam farming.

Here is a link to a Summary
http://www.sciencemag.org/cgi/content/summary/325/5943/952

I have not read the article, but thought it might fit in
with your coastal research.