In a laboratory flume, geometrically different model fishrocks were used to induce scour. Fishrocks are defined as boulders placed in streams to improve fish habitat. Fishrocks create scoured areas in streams by increasing local water velocities near the substrate, which increase the local drag and lift forces that act on the substrate grains. Vortices act as the mechanism of local scour. The complexity of the local scour phenomenon arises from the hydraulic interaction among water flow, large roughness elements, vortices, and a deformable substrate.