FLOOD00847

• County: Statewide
• Community: State of Colorado
• Title: Hydraulic Design of Improved Inlets for Culverts
• Date: 8/1/1972
• Prepared For: State of Colorado
• Prepared By: USDOT
• Floodplain - Doc Type: Educational/Technical/Reference Information

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Acknowledgments

Modifying inlet geometry to improve culvert performance has
been the ambition of many engineers in the last fifty years.
Some of the first culvert research by Yarnell (1) 1 and Mavis (2)
and later investigations at the University of Minnesota (3) and
Oregon State University (4) indicated that additional research
on inlet geometry would be rewarding.

Although a limited number of rounded and enlarged inlets were
built on highway culverts in several States, the Northwest Region
of the Federal Highway Administration (formerly the Bureau of
Public Roads) began building many improved inlets on box and
circular culverts in the early 1950's, primarily on culverts
placed on relatively steep grades. Mr. Carl F. Izzard developed
a theoretical design for a drop-tapered inlet at that time,
and the promotion and use of the improved inlet in the Northwest
led to the research at Oregon State University and comprehensive
investigation at the National Bureau of Standards under the
directio~ of Mr. John L. French and sponsored by the Federal
Highway Administration. Guidance of the research and preliminary
development of the design procedures were performed by Mr. Herbert
G. Bossy, assisted-by others in the Hydraulics and Hydrology
Group, Office of Research, in cooperation with personnel of
the Hydraulics Branch, Bridge Division, Office of Engineering,
both within the Federal Highway Administration.

This Circular was prepared as an integral part of Research
and Development Demonstration Project Number 20, "DemoIl$tration
of Improved Inlets for Highway Culverts, If sponsored by Region 15.
Mr. Johnny L. Morris of Region 15, and Mr. Lawrence J. Harrison
of the Hydraulics Branch, devoted full-time effort to the project.
Mr. J. M. Normann of the Hydraulics Branch, contributed greatly
to the final development of the Circular. The Project 20 Technical
Advisory Committee members included L. A. Herr and F. L. Johnson,
Office of Engineering; W. S. Mendenhall, Jr., and L. M. Darby,
Region 15; C. F. Izzard, Office of Development; and J. M. N9rmann and
R. E. Trent, Office of Research. Mr. Johnny L. Morris was Project
Manager and Mr. Lawrence J. Harrison was Technical Supervisor
for Demonstration Project 20.

lNumbers in parentheses refer to publications listed in
the Selected Bibliography.

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