Three-dimensional flow dynamics and bed morphology around deflectors in a laboratory flume

Although deflectors are commonly used in fish habitat rehabilitation projects to create and/or maintain pools, there is a lack of understanding of the complex flow field and scour patterns around these structures. The objective of this research is to quantify the 3D flow dynamics and the bed morphology around various designs of flow deflectors in a laboratory flume over a plain and mobile bed. 3D velocity measurements were taken with an acoustic Doppler velocimeter. After comparing different methods of bed shear stress estimates, it was determined that the turbulent kinetic energy approach was best at capturing the shear stress amplification near the deflectors. Deflectors oriented perpendicular to the flow create the most important disturbance of the flow field, the greatest increase in turbulence intensity and the largest scour hole, followed by upstreamoriented deflectors (135°) and downstream-oriented ones (45°). 90° deflectors would therefore potentially provide the greatest benefit for fish habitat rehabilitation