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<br />e <br /> <br />, <br /> <br />e <br /> <br />. <br /> <br />'"' J <br />,"", <br />.. <br /> <br />e <br /> <br />PREFACE <br /> <br />The purpose of this circular is to provide procedures for the design of <br />encroachments on flood plains using risk analysis. The application of risk <br />analysis to the design of drainage structures allows the designer to select <br />that design which will result in the least total expected cost to the public. <br />The use of risk analysis in the design of drainage elements for transportation <br />facilities is an evolving technology. The methodology presented in this manual <br />should be viewed as a first step and users are encouraged to seek improved or <br />new methods and uses for the application of risk analysis in drainage design. <br /> <br />The material is presented in sections which are arranged in the step-by-step <br />order which should be followed in analyzing a proposed crossing. The last <br />section is a sample report outline which can be used to organize any analysis <br />performed using the procedure. Example problems which illustrate the procedure <br />are included in the appendices. <br /> <br />ACKNOWLEDGEMENTS <br /> <br />The concepts in this circular are based on the research and development <br />efforts in FHWA-TS-80-226, "Hydraulic Design of Bridges with Risk Analysis," <br />by V. R. Schneider and K. V. Wilson of the U.S. Geological Survey and <br />FHWA-RD-75-54, "Evaluation of Flood Risk Factors in the Design of Highway <br />Stream Crossings," by f':. T. Tseng, A. J. Knepp, and R. A. Schmalz. <br /> <br />The authors are indebted to Messrs. Schneider and Wilson for sharing the <br />background material and data used in their publication. Mr. Schneider's <br />review of this circular is also greatly appreciated. Mr. Dan O'Connor, FHWA, <br />Region 6, Hydraulics Engineer, contributed substantially to this effort by <br />reviewing the circular and by formulating the innovative preliminary analysis <br />of risk shown in section 2.0. In addition to those mentioned above, the <br />circular ~Ias improved by the peer review of v'r. Larry Harrison, FHWA, Region 8, <br />Hydraulics Engineer, Mr. Mainard Wacker, Wyoming Highway Department, and <br />Messrs. Delbert Roupp, Lawrence E. Dezman, and Steven Buchberger, Colorado <br />Division of Highways. <br /> <br />The authors wish to express special thanks to Ms. Barbara Driver who typed <br />the manuscri pt. <br /> <br />~ <br />