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• intensity curve for storms in the Weston, Colorado, area <br />having a probable fraquency interval of 10 years was used to <br />predict the peak runoff. The rainfall duration-intensity <br />curve was developed using the Rainfall Intensity Atlas . <br />Because the Atlas has only limited durations (30-min, 1-hr, <br />etc.) a closest, least-squares fit, logrithmic curve using <br />extrapolation guidelines, also from the Atlas, was developed <br />for the rainfall durations from 5 to y0 minutes, for one <br />minute intervals. This curve, though only an estimate, gave <br />better rainfall intensities for the small drainage areas. <br />Using only the 30-minute intensity available directly from <br />the Atlas would give unacceptable results. The curve is <br />included with the calculation print-outs. The total volume <br />• of runoff from a 10-year-24-hour storm event was calculated <br />using a total rainfall of 3.0 inches taken directly from the <br />Atlas. <br />The computer program developed for these calculations calls <br />for the required parameters to evaluate the runoff. The <br />inpu*. parameters for calculating runoff are: <br />Acres of land in the basin, <br />Length of overland flow across the basin, <br />Slope of the baisn, <br />Runoff coefficient, water absorption, <br />Retardance coefficient, flow rate, <br />Chart Number, topsoil conditions, <br />• Time of Concentration, estimate for determination, <br />Total Rainfall for storm event, 10-yr-2U-hr. <br />23 <br />