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. September 1934, stage was measured several times a day. Therefore, determining the rainfall contribution to the peak flow for June 14, 1921 can not directly be determined from hydrograph separation (Linsley and others, 1982) as has been done extensively for streams in Colorado (Jarrell, 1987). An approximation of rainfall-runoff contribution to the peak flow was estimated by interpreting graphs of average daily discharge for June 1921 and the associated annual-peak flow. Graphs for streams in northwestern Colorado where streamflow-gaging stations were in operation are shown in figures 16b- 16d. Antecedent snowmelt runoff was interpreted from the average daily flow, The estimated net peak flow from rainfall runoff is shown on figures 16b-16d. The maximum rainfall runoff was less than about 800 ft3/S, except for the Yampa River at Steamboat Springs where it ranged from about 950 to 2,000 ft3/s (range from uncertainty of antecedent snowmelt on June 14). Thus, rainfall runoff contributed from 15to 30 percent to the total peak flow of 6,820 ft3/S. The volume of rainfall runoff is approximately the same for the Yampa River near Maybell, which drains the entire area subject to this rainstorm, as the volume of rainfall runoff at the Yampa River gage at Steamboat Springs, Thus, it appears most rainfall runoff was limited to streams in Steamboat Springs with decreasing contributions at lower elevations (Yampa River near Maybell, White river near Meeker), Rainfall runoff in June 1921 on the White River near Meeker (figure 16d) and Elk River at Clark was minimal (figure 16c). Although it is difficult to estimate the contributing area for the June 14, 1921 rainstorm using the available streamflow and rainfall data, an approximation can be inferred if the paleoflood data also are utilized . (Jarrell, 1990b). The lack of substantial paleoflood evidence in tributary streams to the Yampa and Elk Rivers (table 1) also indicates that the 1921 rainstorm was limited in amount and areal extent Because no substantial out-of-bank flood evidence exists, reported flooding in Steamboat Springs probably resulted from undersized culverts and bridges that became clogged with debris. The greatest contribution of the rainfall runoff probably occurred in the developed areas (rooftops, gravel roads) within town. It may be that several small tributaries located in Steamboat Springs had a unit discharge in excess of 100 ft3/slmj2 to perhaps a maximum of 200 ft3/slmj2. This range of unit discharge falls within the envelope curve for northwestem Colorado (figures 10a and 10b). I suspect that the storm was elliptically shaped. The length probably was about 10 to 15 mi in length oriented parallel to the Yampa Valley and about 2 to 2.5 mi wide. The contributing area probably ranged from 20 to 30 mi2. Had the rainstorm extended farther downvalley, then the 1921 rainfall runoff peak and volume would have been substantially greater for the gage at Yampa River near Maybell than at Steamboat Springs. The analysis to determine the approximate net rainfall runoff also was done for all years for the Yampa River at Steamboat Springs to determine if other rainstorms may have had similar or larger rainfall runoff than 1921. The average-daily flow (ADF) on the day of the annual peak flow (Op) was subtracted from the instantaneous peak for each year (figure 16e). Thus, ADF is used as an approximation of antecedent snowmelt runoff. Since 1904, only three other years have had a rainfall contribution to peak flow larger than 1,000 ft31s (figure 16e). Because of physical constraints on maximum snowmelt runoff, at some point . the contribution from rainfall for extreme (> 1 DO-year events) would increase, However, the maximum paleoflood of about 1 0,000 ft3/S estimated for the Yampa River at Steamboat Springs (lable 1) is a 26