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frequency curve. Tho adjustment from partial-to-annual series is performed by multiplying the rainfall depths for each duration by the appropriate conversion factor. The conversion factors are as follows: SERIES 2-YEAR 5-YEAR la-YEAR FACTOR 0.88 0.96 0.99 No adjustment is needed for rarer return intervals since the two curves coincide after the 1 o-year event. At this point, all adjustments have been made. The nex1 step is to proceed through further breakdown and arrangement of the hypothetical storm. 3.6. DIVISION INTO INCREMENTAL VALUES. One now takes the adjusted rainfall values for a particular storm (there are usually six values) and further subdivides these to arrive at a rainfall depth value for each time increment (for example, there will be twenty-four values for the 6-hour-duration l5-minute-interval case). This division into increments is usually performed by plotting the values of rainfall depth (in inches) versus duration (in minutes) on logarithmic paper, fitting a curve through these points, and then reading off accumulated depth values for each increment from the curve. Averaging the incremental change between the original points is usually a satisfactory alternative, since the depth-duration picot normally approximates a straight line after the first several values. Once an accumulated depth for each interval has been determined, the depths are incremented to compute that portion of the depth that occurred in each period. 3.7. STOR'" ARRANGEMENT. The final step in the storm definition is arrangement of the storm rainfall into a specific pattern. The pattern used most often by the Corps of Engineers is a 'triangular" arrangement, with the peak period in the center of the storm. For out example, for a 24-hour duration storm with a computation interval of 15 minutes, the peak l5-minute depth would be placed in (assigned to) the thirteenth hour or forty-ninth period of the twenty-four period storm sequence. The nex1-highest depth is placed just ahead of the peak (Period 48), the nex1 highest depth just behind (Period SO), and so on until all 96 values are systematically arranged about the peak period. If a storm with a duration longer than 24 hours is to be arranged, all 24-hour periods outside of the peak 24 hours can be represented by an average value for each 24- hour period, The rainfall increments cannot be moved outside the 24-hour period from which the increment was developed, however. An alternative method commonly used along the Front Range to temporally distribute rainfall amounts is to place the larger incremental amounts more heavily towards the front of the design storm. This method is based on the observation that very intense rainfall in the area results from convective storms or frontal stimulated convective storms. Colorado Flood Hydrology Manual DRAFI' 7.6