Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)


Electrical Engineering


Many mathematical models have been developed to help the hydraulic engineer with respect to sediment transport. Some models have been found to be better than others in specific applications; however, HEC-6 Scour and Deposition in Rivers and Reservoirs has proved to be a very useful model for a wide variety of applications. The flexibility, adaptability, usability, portability and expandability of the model has led to it being used in many federal, state, private, and academic agencies. Each agency, having its own interests, has adapted and expanded the model for their needs. One such expansion was performed by Dr. Alan Prasuhn, Professor of Civil Engineering, South Dakota State University, Brookings, South Dakota. Funding was provided by the Office of Water Research and Technology, U.S. Department of the Interior, Washington, D.C. to study the modeling of scour and backwater at highway bridges due to debris accumulation. To complete Prasuhn's study it was necessary to expand the model to include larger sediment sizes, introduce additional transport functions, add pier scour equations, and incorporate a bridge hydraulics routine. The bridge hydraulics routine was necessary to simulate flow and sediment transport conditions when the water surface impinges on the bridge deck. Under these conditions, pressure flow under the bridge occurs and the validity of the sediment transport equations is in question. Because of the uncertainty in this area, a series of laboratory experiments were performed to verify the model in this application. The procedures used and results obtained in the laboratory are presented in this paper. Clear water was discharged into a flume with a sand bed and the water surface was forced to impinge on a simulated bridge deck. Photographs of the adjustment to the water surface and bed profiles with respect to time were taken through the plexiglass walls of the flume. The experimental results were then compared with the results obtained from the model operating with the same sediment, geometric, and hydrological conditions. Nine experimental trials were performed. Four trials and their comparison with the model are presented in Chapter 4 of this paper. Using the same laboratory equipment, another experiment was conducted to verify the armoring characteristics in the model. During the initial time periods, the model assumes the material in the bed to be uniformly distributed. Most often this is not the case in a natural stream.

Library of Congress Subject Headings

Sediment transport -- Mathematical models
Scour at bridges
Bridges -- Foundations and piers
South Dakota State University Theses



Number of Pages



South Dakota State University