Groynes

Fixed structures extending out from the seawall used to control erosion or promote deposition.
Found on http://www.encyclo.co.uk/local/20493

groynes

Low walls built perpendicular to a shoreline to trap sediment, such as sand, drifting along the shore. Groynes are usually made of wood, concrete or piles of large rocks.
Found on http://www.conservancy.co.uk/learn/wordlist.htm
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