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<br />PREFACE <br /> <br />The design information in the first edition of "Hydraulics of Bridge Waterways," <br />published in 1960, was based principally on the results of hydraulic model studies <br />and was definitely limited in its range of application, Over the intervening 10 years <br />the U.S, Geological Survey has taken measurements and collected field data on the <br />hydraulics of bridges during floods, Upon examination of the field data it was <br />deemed advisable to reevaluate the model results to determine the actual limits of <br />application and then utilize the field data to complete the design curves, <br />This edition thus contains revisions to some of the design curves. A considerable <br />amount of new material has been added such as chapters on partially inundated <br />superstructures, the proportioning of spur dikes at bridge abutments, and super- <br />critical flow under a bridge, together with examples, An appendix has also been in- <br />cluded to show how the general expressions for bridge backwater were derived and <br />to explain how and why changes were made to some of the former design curves, <br />The field results have added considerably to the reliability of the information con- <br />tained herein, <br />Mr, Lester A, Herr, Chief of the Hydraulics Branch, Bridge Division, requested <br />and 8upervised the preparation of this revised edition of the "Hydraulics of Bridge <br />Waterways," Many thanks go to Mr, Herr and Mr. J, K Searcy of his staff for <br />their time and helpful suggestions in the technical editing of the present edition, <br />The research program on bridge waterways, which was the basis of the first edition, <br />was directed by Carl S, Izzard, then Chief of the Hydraulics Research Division of <br />the Bureau of Public Roads. The writer, who served as project supervisor, is greatly <br />indebted to Mr, Izzard for his gifted guidance and timely suggestions. <br /> <br />iii <br />