Riprapping on the Wabash River in 2001. Riprap, also known as rip rap, rip-rap, shot rock, rock armor, or rubble, is human-placed rock or other material used to armor shorelines, streambeds, bridge abutments, pilings and other shoreline structures against scour and water, wave, or ice erosion. Common rock types used include granite and modular concrete blocks. Rubble from building and paving demolition is sometimes used.