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Abstract
A wide range of human activities in river environments requires emplacement of in-stream unsubmerged deflection structures (ISUDS) which include groynes, spur dikes, abutments, and temporary structures such as riprap construction platforms. Improved understanding of the hydraulic and geomorphic effects of ISUDS is essential for minimizing unintended consequences such as channel erosion and habitat alteration. Hydraulic modeling and statistical analyses were conducted to assess effects of ISUDS on channel velocities and shear stresses. Over 50,000 HEC-RAS model simulations were performed using variable contractions, discharges, Manning n values, and realistic channel geometries. Practical regressions that predict mean changes in velocity and shear stress due to emplacement of ISUDS were developed. Two-dimensional modeling was also performed to analyze spatial patterns of amplified velocities and shear stresses resulting from ISUDS. These hydraulic modeling results can be used in conjunction with the novel regressions to inform preliminary ISUDS design, environmental management, and regulatory decisions.