Riprap
shoreline armouring structure
Riprap (in North American English), also known as rip rap, rip-rap, shot rock, rock armour (in British English) or rubble, is human-placed rock or other hard, heavy, unconsolidated material used to protect shoreline structures against scour and water, wave, or ice erosion. Riprap is used to armor shorelines, streambeds, bridge abutments, foundational infrastructure supports and other shoreline structures against erosion. Common rock types used include granite and modular concrete blocks. Rubble from building and paving demolition is sometimes used, as well as specifically designed structures called tetrapods or similar concrete blocks.
Riprap is also used underwater to cap immersed tubes sunken on the seabed to be joined into an undersea tunnel.
Design and installation
Riprap design takes into account the size and gradation of the rock, the thickness of the protective layer, water flow and wave conditions, the slope being protected and the characteristics of the underlaying soil. Rock size is commonly described using D50, which represents the median particle size in a graded riprap mixtures.
Riprap generally consists of a range of stone sizes rather than uniformly sized rocks. The stones are placed to form a stable protective layer while still allowing the water to move through the spaces between them. Where necessary, a granular filter layer or geotextile is installed beneath the riprap to reduce the loss of soil particles and help prevent the layer from being undermined.
The public source identifies “Riprap” as shoreline armouring structure. This brief keeps that definition visible, then builds a research path around Riprap, shoreline and armouring.
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Named sources, stable identifiers and responsible institutions provide the strongest route from overview to verifiable evidence. The source revision retrieved here is dated Sep 8, 2026. The linked authority identifier is Q3433064. None of the 0 selected statements returned an explicit reference.
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This entry incorporates text from “Riprap” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.