Predicting velocity in bendway weir eddy fields

Abstract

AbstractRehabilitation of the Middle Rio Grande (MRG) in central New Mexico has become necessary because of changes in morphology resulting from the installation of dams, and because of habitat restoration considerations for the endangered Rio Grande silvery minnow (Hybognathus amarus). Bendway weirs are erosion control and channel‐stabilization structures placed transverse to the channel flow that have been increasingly used to prevent river migration while simultaneously enhancing aquatic habitat. Plans for rehabilitation along the MRG include the use of bendway weirs; however, past projects using these structures have relied on field experience and engineering judgment rather than specific design guidelines. A physical model of a reach of the MRG was constructed to develop empirical design equations for eddy velocities in bendway weir fields. Data from physical model simulations were used to develop two empirical expressions for predicting eddy velocities behind bendway weirs, along with two expressions for predicting velocities at the toe of installed weirs. These equations relate the velocity found after bendway weir installation to weir design characteristics and pre‐weir channel conditions. A designer can use the described approach to predict velocities in eddies and velocities at the toe of bendway weirs using only weir design variables and pre‐weir channel conditions, and thus avoid some of the uncertainty with weir design that previously existed. Copyright © 2009 John Wiley & Sons, Ltd.