Look up riprap in Wiktionary, the free dictionary.
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 material used to protect shoreline structures against
scour and water, wave, or ice erosion.[1][2][3] Riprap is used to
armorshorelines, streambeds, bridge
abutments, foundational infrastructure supports and other shoreline structures against erosion.[1][2][3] Common rock types used include
granite and modular
concrete blocks.[4][5]Rubble from building and paving demolition is sometimes used,[3][6] 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.[citation needed]
Environmental effects
Sediment effects
Riprap causes morphological changes in the riverbeds they surround. One such change is the reduction of sediment settlement in the river channel, which can lead to scouring of the river bed as well as coarser sediment particles. This can be combatted by increasing the distance between the pieces of riprap and using a variety of sizes.[7]
The usage of riprap may not even stop erosion, but simply move it downstream.[8] Additionally, the soil beneath the riprap can be eroded if the rock was just placed on top without any buffer between the layers such as a
geotextile fabric or smaller riprap (
crushed stone).[9]
Changes in organic material and the ecosystem
Riprap affects the amount of organic material in a waterbody by acting as a filter, catching wood and leaves before they can enter the water.[8] Riprap also covers and prevents plants from growing through, which can reduce shade over the water.
Introducing ripraps creates a rocky environment which can affect the
ecology of a waterbody by making the ecosystem more heterogeneous.[10] While it can negatively affect some
organisms by removing shoreline vegetation, the rock can provide important refuge for
invertebrates and small
fish.[8][11] By preventing woody plants from growing and shading the water, riprap can also increase the amount of
algae and
hydrophytes.[12]