Maximum Velocity Effects from Vane-Dike Installations in Channel Bends

Abstract

Channel bends are associated with secondary, helical currents, shifts of conveyance to the outer channel, and variable lateral sedimentation patterns. Outer-bank erosion is of primary concern, resulting in stream-course migration that may place valuable infrastructure and land holdings in jeopardy. In such cases, in-stream river structures such as vane dikes are commonly implemented to restrict the channel course to desired boundaries. Vane dikes are normally installed in series, extending laterally from the outer channel bank into the stream, thereby reducing flow velocity at the outer bank and increasing flow velocity along the channel center and inner bank. Flows around vane dikes and similar transverse in-stream structures have been modeled both numerically and physically in the past, yet the effects on flow velocity within a channel bend due to vane-dike installations have not yet been fully realized. With a focus on the stabilization of two channel bends in the upper regions of the Rio Grande River, a scaled physical model was constructed for the evaluation of various vane-dike field configurations. Structure plan-form angle, spacing, and length were altered between configurations and comprehensive hydraulic data were collected at flow depths below, at, and above structure height. To address flow velocity effects from the structures, a dimensional analysis of influencing parameters was performed, and maximum conditions were used for regression analyses. A series of equations were generated which represent maximum changes in flow velocities at the outerbank, inner-bank, and centerline locations within a channel bend from the installation of vane-dike fields.