Optimal Configuration of Rock Vanes and Bendway Weirs for River Bends: Numerical-Model Insights

Abstract

Presented are insights from three-dimensional numerical models used to identify optimal performance configurations of rock vanes and bendway weirs placed in midsize rivers, such as the Middle Reach of the Rio Grande. These transverse instream rock structures are used to control channel thalweg alignment and reduce flow velocity near the outer bank of river bends. The numerical models (validated and verified using a hydraulic model) showed rock vanes to be considerably more effective at reducing near-bank velocity than bendway weirs. Optimal-performance configurations of rock vanes were found be (1) planform angle (relative to adjacent upstream bank) of 45° to 85°; (2) structure spacing of 3/4th of channel top width (bank full); and (3) structure projected length of 1/5th to 1/3rd of channel top width (bank full). Additionally, velocity at the tip of both rock vanes and bendway weirs more than doubled compared with the baseline velocity along the outer bank. The insights lead to a layout guideline, based on hydraulics considerations, for series of rock vanes and bendway weirs.