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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 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 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 /> INPUT 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-24-HR . <br /> 30 <br />