Abstract: A system of structures uses the energy and properties of a stream flow to protect downstream structures from various potentailly damaging stream-flow-induced events. One element, a streamwise-vortex generator is placed upstream from a structure to protect it from impact by buoyant contaminates. The generator is positioned at a depth sufficiently below the surface to minimize the likelihood of contact with vehicles or debris. In this position it induces a vortex in the current flow whose axis is essentailly parallel to the streamwise flow. The vortex persists downstream of the generator and, migrating to the surface, deflects a debris away from the protected structure. Another element, a vorticity generator, causes interference with, and/or diversion of streambed-scouring vortices or eddies which are naturally generated adjacent the sides of structures. The result is protection of the streambed from damaging scour which would otherwise occur.