Date of Award:

1997

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Civil and Environmental Engineering

Advisor/Chair:

Thomas B. Hardy

Abstract

The Logan River was used as a study site to assess the capabilities of two-dimensional depth-averaged hydraulic modeling in the x-y plane of a natural river for use with instream flow studies. Data were collected to spatially represent the study reach with depth, velocity, northing, easting, elevation, and substrate values using a total station and electronic velocity meter. Computational finite element meshes were generated using four different density levels of geometry data to examine the relationship between field data density and computational mesh on geometry errors. Geometry errors were found to be related to smoothing effects, which removed complex channel geometries while overall mesh geometry errors were related to data density in homogeneous versus heterogeneous channel conditions.

Results indicate that required field data can be optimized with lower data densities in homogenous sections of the river channel. Of the two hydraulic models examined, the U.S. Army Corps of Engineers RMA2 model could not be adequately calibrated given the high slope within the study reach and therefore all subsequent evaluations were made utilizing the CDG2D model. CDG2D model performance was best in the lower gradient sections of the test section at both calibrated and simulated flows with increasing errors for water surface and associated depth and velocity errors as channel gradient increased. These results suggest that additional research is needed to define limiting gradients under which application of this class of hydrodynamic model can be expected for practical instream flow assessments.

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