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HAVING A PROBABLE FRAOUENCY INTERVAL OF 10 YEARS WAS USED TO <br /> PREDICT THE PEAK RUNOFF. THE RAINFALL DURATION-INTENSITY <br />~ <br />C <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 CUPVE USING <br /> EXTRAPOLATION GUIDEI.INFS. ALSO FROM THE ATLAS. WAS DEVELOPED <br /> FOR THE RAINFALI. DURATIONS FROM S TO 40 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 3O-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 lO-YEAR-24-HOUR STORM EVENT WAS CALCULATED <br /> USING A TOTAL RAINFALL OF 3.0 INCHES TAKEN DIRECTLY FROM THE <br /> ATLAS. , <br />i _ <br /> THE COMPUTER PROGRAM DEVELOPED FOR THESE CALCULATIONS CALLS <br /> FOR THE REQUIRED PARAMETERS TO EVALUATE THE RUNOFF. THE <br /> INPUT PARAMETERS FOP, 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 FOt; STORM EVENT, lO-YR-24-HR. <br />L 30 , <br />