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<br />many locations as possible. Determine unit hydrograph or kinematic wave <br />pBrameters, loss-rate parameters, beginning flow rates, and recession <br />characteristics which do the "best" job of reprooocing the observed <br />hydrographs. Adopt representative values of these parameters. Optimization <br />features of the HEC-l IIKldel are normally used for this step. <br /> <br />e <br /> <br />(2) Regionalize Basin Parameters <br />Perform regression studies on unit hydrograph parameters and basin <br />physical charBcteristics using the procedures given in Chapter 6. <br /> <br />(3) Develop Streamflow Frequency CUrves for Gaged Sites <br />If any of the stream gages studied are near the basin of interest, <br />perform discharge-frequency analyses on the annual series of observed maximum <br />discharges. <br /> <br />(4) Model the Study Area <br />a, Subdivide the study basin into as many subbasins as are <br />necessary to establish index points for each stream reach where discharge- <br />frequency estimates are required. Determine the drainage area and other <br />physical characteristics of each subbasin and adopt unit hydrograph or <br />kinematic wave parameters for eBch, based on the regional studies of Step (2). <br /> <br />e <br /> <br />b, Determine channel length between index and/or combining points <br />and estimate channel routing characteristics either by detailed field <br />surveys, stream cross-section and multiple-discharge water surface profile <br />studies, or any acceptable approximate means commensurate with the scope of <br />the study. Adopt channel routing parameters, <br /> <br />c. Assemble subarea data decks for the HEC-l runoff model for <br />several historical storms Bnd adjust loss parameters and routing parameters <br />to best reproduce the observed hydrographs at gaged points. <br /> <br />(5) Develop Hypothetical Events <br />Derive rainfall frequency curves using the procedures described in <br />Chapter 4, for various rainfall durations (SBY durations of 1, 3, 6, 12, and <br />24 hours). For a selected storm frequency, determine rainfall depths for <br />each duration at desired time intervals, compute incremental depths, and <br /> <br />e <br /> <br />14 <br />