THESIS TITLE: EFFECTS
OF BENDWAY WEIR CHARACTERISTICS ON RESULTING EDDY AND CHANNEL FLOW CONDITIONS
processes associated with rivers lead to channel meandering and degradation,
bank erosion, and the migration of river bends. Traditionally, armor protection
and longitudinal structures have been used to prevent river migration. In
the last twenty years, bendway weirs, a type of transverse structure, have
been used to prevent river migration and concurrently create aquatic habitat.
River rehabilitation along the
Middle Rio Grande has become necessary due to changes in morphology resulting
from the installation of the Cochiti Dam. Cochiti Dam has trapped nearly all
river sediment causing a 29-mile reach downstream to shift from a traditionally
braided system to a meandering system. The agency responsible for the rehabilitation
of the 29-mile reach is the U. S. Bureau of Reclamation (USBR). Plans for
rehabilitation include the use of bendway weirs. Past projects utilizing bendway
weirs have relied on field experiences and engineering judgment rather than
specific design guidelines.
Based on the need for bendway weir
design equations, the USBR commissioned a model study at the Hydraulics Laboratory
of the Colorado State University Engineering Research Center. To study resulting
flow conditions from the placement of bendway weirs, an undistorted 1:12 Froude
scale, hard boundary model was constructed. The model contained two bends
representative of bends found in the Middle Rio Grande study reach. Three-dimensional
velocities were recorded for a series of tests in which weir length, weir
angle, and weir spacing were varied.
Using data obtained from the test
series, two equations were developed to predict eddy velocities and two equations
were developed to predict velocities at the toe of installed bendway weirs.
Equations relate the velocity found after bendway weir installation to bendway
weir design characteristics and pre-weir channel conditions. Utilizing the
developed equations, a designer is able to predict velocities in eddies and
velocities at the toe of bendway weirs using only weir design variables and
pre-weir channel conditions.
GRADUATION DATE: Spring 2005