Overtopping - Passing of water over a structure from wave runup or surge action.
Peat - Residual product produced by partial decomposition of organic matter in marshes and bogs.
Peat Pot (vegetation) - Pot formed from compressed peat and filled either with soil or peat moss in which
a plant or plants, grown from seed, are transplanted without being removed from the pot.
Perched Beach - Beach or fillet of sand retained above the otherwise normal profile level by a submerged
dike or sill.
Permeable - Having openings large enough to permit free passage of appreciable quantities of (1) sand or
(2) water.
Pile - Long, heavy section of timber, concrete or metal driven or jetted into the earth or seabed as support
or protection.
Pile, Sheet - Pile with a generally slender, flat cross section driven into the ground or seabed and meshed
or interlocked with like members to form a diaphragm, wall, or bulkhead.
Piling - Group of piles.
Plug - Core containing both plants and underlying soil, usually cut with a cylindrical coring device and
transplanted to a hole cut by the same device.
Polyvinyl Chloride (PVC) - Plastic material (usually black) that forms a resilient coating suitable for
protecting metal from corrosion.
Profile, Beach - Intersection of the ground surface with a vertical plane that may extend from the top of
the dune line to the seaward limit of sand movement.
PVC - See POLYVINYL CHLORIDE.
Ravelling - Progressive deterioration of a revetment under wave action.
Refraction (of water waves) - (1) Process by which direction of a wave moving in shallow water at an
angle to the contours is changed. Part of the wave advancing in shallower water moves more slowly than
the part still advancing in deeper water, causing the wave crest to bend toward alignment with the
underwater contours. (2) Bending of wave crests by currents.
Revetment - Facing of stone, concrete, etc., built to protect a scarp, embankment, or shore structure
against erosion by waves or currents.
Rhizome - Underground stem or root stock. New shoots are usually produced from the tip of the
rhizome.
Riprap - Layer, facing, or protective mound of stones randomly placed to prevent erosion, scour, or
sloughing of a structure or embankment; also, the stone so used.
Rubble - (1) Loose, angular, waterworn stones along a beach. (2) Rough, irregular fragments of broken
rock or concrete.
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