A review of bridge scour mitigation measures using flow deflecting structures

Bridges overhead rivers require exceptional safety and channel rehabilitation due to the erosive impact of water. There has been a lot of research into designing efficient countermeasures for scour protection and treatment of channel instability near bridges. Interestingly, most of these studies use flow-modifying structures to regulate flow and sediment migration on the upstream side of bridges. Notably, the flow-modifying structures are proven to be effective tools in bridge pier protection since their working premise is the counteracting of vortices or realignment of flow. Hence, to develop proper knowledge, this paper focuses on flow deflecting structures with the aim of modifying flow by realignment. The study begins with an evaluation of several hydraulic challenges associated with modern bridges worldwide. Thereafter, the literature featuring flow deflecting devices, such as submerged vanes, rock vanes, cross vanes, and w-weirs, is discussed. In doing so, the fundamentals of how these devices restore the flow by keeping the maximum scour depth away from the bridge abutment and pier are addressed. Further, the capabilities of the flow deflecting devices on smooth and safe flow transfer through bridge openings are highlighted. In addition, a thorough examination of bridge safety during pressure flow is included in the study.