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<br />VARIABLE UNITS USE <br />precipitation values 1-HR or hyetograph <br />retum period 2-, 5-, 10-, 50- or 100- if 1-HR storm selected <br /> year <br />initial infiltration rate inches/hour optional <br />Horton's infiltration decay number optional <br />exponent <br />final infiltration rate inches/hour optional <br />rational formula use if catchment < 90 Acres optional <br />duration of rainfall 5 or 10 minute <br />increments <br />catchment area square miles <br />catchment length miles <br />distance to centroid miles <br />catchment percent <br />imperviousness <br />weighted catchment feet/foot <br />slope <br />time of concentration minutes (Rational optional <br /> method) <br />depression storage on inches <br />pervious surfaces <br />depression storage on inches <br />impervious surfaces <br />level of minimized directly 1,2 or 3 optional <br />connected impervious <br />area <br />directly connected number optional <br />impervious fraction <br />receiving fraction of number optional <br />pervious area <br /> <br />Table 1. CUHP Standard Variables <br /> <br />The UDFCD recommends this procedure for catchment sizes of up to 5 <br />square miles. Larger catchments should be subdivided. The Rational Formula is <br />recommended for catchments between 5 and 90 acres. Long catchments <br />(Iength-to-width ratios greater than 4) should also be subdivided. Adjustments <br />are recommended for catchments with exceptionally steep slopes~ <br />This investigation was not concerned with either the directly connected <br />impervious area or the water quality functions of the program. Due to the highly <br />developed nature of the Gatchment, it was assumed that all of the impervious <br />areas were directly hydraulically connected to the drainage system. <br /> <br />Application and Evaluation of CUHP <br /> <br />Page 4 of 52 <br />