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<br />OOlG96 <br /> <br />36.2--1 <br /> <br />WATER INFORMATION MANAGEMENT SYSTEM HANDBOOK <br /> <br />I <br />\ <br /> <br />36.2 - Appendix B - Common Steps for Calculating the Required Maintenance <br />rTOW Hydrograph. <br /> <br />Step 1. Representative Gaged Station Flow-Duration Curve Construction for <br />the Graphic Determination of Channel Maintenance Flow Components. <br /> <br />a. Constructing the Normalized Flow-Duration Curve. <br /> <br />(1) Using the duration table of daily values summary obtained from <br />USDI Geological Survey data sources for the representative station, divide <br />the CFS values given in the listed table classes by the calculated <br />bankfull discharge value (QB), to develop a ratio. In the example, <br />these ratio values are shown in exhibit 1 (column 6). <br /> <br />(2) Construct the flow-duration curve (normalized) by plotting the <br />calculated ratio values (column 6) versus the percent time value (column <br />5) for each class in exhibit 1. Connect plotted points with a smooth <br />curve (ex. 2). <br /> <br />b. Graphic Determination of Instreamflow Components. <br /> <br />(1) Bankfull: Beginning with the ratio value of 1.0 on the y-axis of <br />the flow-duration curve (bankfull discharge, QB/QB), extend a <br />horizontal line to intersect the flow-duration curve (ex. 2). Extend a <br />vertical line from this interesect down to the percent time scale (x-axis) <br />and read the percent time value fOr which bankfull flows are equaled or <br />exceeded. This time increment becomes the duration of bankfull discharge, <br />QB' For this example, this time increment is 1.74 which is equivalent <br />to a duration of 6.2 days. <br /> <br />(2) locate along the flow-duration Curve the pOint which represents <br />the ratio value of QA/QB' <br /> <br />(3) locate along the flow-duration Curve the point which represents <br />the ratio value of QlI/QB' <br /> <br />(4) locate along the flow-duration curve the point which represents <br />the ratio value of Ql2/QB' <br /> <br />(5) Rise-Recession Flows: Considering that segment of the <br />flow-duration curve between the bankfull point and the QA/QB point, <br />the rising-recession flow steps are located as follows: <br /> <br />1D No. 1 <br />9/10/85 <br />