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<br />HEC-2 <br />WATER SURFACE PROFILES <br /> <br />USERS MANUAL <br /> <br />I NTRODUCTI ON <br /> <br />1. PROGRAM DEVELOPMENT <br /> <br />The HEC-2 computer pr09ram was developed in the Hydrologic Engineering <br />Center by Bill S. Eichert. The version documented herein, dated Novem- <br />ber 1976, is intended to replace all earlier versions. The basic com- <br />putational capabilities for calculating water surface profiles and the <br />data input requirements remain essentially unchanged. However, capabil- <br />ities have been added for a) encroachment analysis (methods 5 and 6), <br />b) summarizing output with pre-defined or user-defined summary tables, <br />c) creating a permanent record of study results on an "archival" tape <br />and d) calculating friction loss with one of five alternative approaches. <br />The version also has reduced storage requirements and increased poten- <br />tial for usage on interactive computer terminals. <br /> <br />2. OVERVIEW OF PROGRAM CAPABILITIES <br /> <br />The program is intended for calculating water surface profiles for steady <br />gradually varied flow in natural or man-made channels. Both subcritical <br />and supercritical flow profiles can be calculated. The effects of vari- <br />ous obstructions such as bridges, culverts, weirs, and structures in the <br />flood plain may be considered in the computations. The computational <br />procedure is based on the solution of the one-dimensional energy equation <br />with energy loss due to friction evaluated with Mannin9's equation. The <br />computational procedure is generally known as the Standard Step Method. <br />The program is also designed for application in flood plain management <br />and flood insurance studies to evaluate floodway encroachments and to <br />designate flood hazard zones. Also, capabilities are available for <br />assessing the effects of channel improvements and levees on water surface <br />profiles. Input and output units may be either Engl ish or Metric. <br /> <br />3. SUPPLEMENTARY PROGRAM <br /> <br />A data edit program (723-GI-L202C) which checks the data cards for vari- <br />ous input errors is available. <br /> <br />1 <br />