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The following section briefly describes some of the major storm events that have crop losses were suffered on lands outside the floodplain which were dependent on caused flooding on South Boulder Creek (Reference 2). Due to the relatively irrigation diversions from Boulder Creek. undeveloped nature of the South Boulder Creek basin, information and observations related to major flood events is somewhat lacking in comparison to the adjacent, 31 August - 4 September, 1938 more heavily developed Boulder Creek floodplain. This storm produced general rains over all of eastern Colorado. The largest FLOOD of 29 May - 2 June, 1894 amounts of precipitation occurred in the mountains where more than 6 inches was reported west of Eldorado Springs. Eldorado Springs recorded 4.42 inches of Heavy rains fell over the mountains extending from the Colorado-Wyoming border rainfall . Approximately 80 percent of the total precipitation falling in the southward into the Republican and Arkansas River basins. Rainfall over the South Boulder Creek basin fell in the late afternoon and evening of September Boulder and South Boulder Creek basins was particularly heavy. Rainfall records 2nd. The resulting flood, with a peak discharge of 7 ,390 cfs passed through for a 96-hour period ending at 3 a.m. on 2 June, 1894 indicate that the mountain Eldorado Springs at 10:00 p.m. on September 2nd. The resort community of drainage area received from 4.5 to 6.0 inches of precipitation. Rainfall amounts Eldorado Springs suffered heavy damage and numerous buildings were destroyed when over the high plains gradually decreased from west to east and varied from 5 flood waters eroded their foundations. The valley from Eldorado Springs to inches at Boulder to approximately 2.5 inches at the mouth of Boulder Creek. The Boulder Creek and down Boulder Creek to St. Vrain Creek was in shambles. This mountain rainfall combined with the snowmelt runoff produced the greatest flood flood is the highest recorded flood on South Boulder Creek. known at Boulder, inundating the valley during the night of 30 May, 1894. Buildings, bridges, roads , and railroads were washed away. Computations made 18 4-8 May 1969 years later produced estimates of the peak discharge on Boulder Creek in Boulder that ranged from 9,000 cubic feet per second to 13,600 cubic feet per second. Flooding in May of 1969 resulted from a long duration general storm. Runoff The Eldorado Springs stream gaging station was not functioning during this flood resulted from a combination of rainfall and snowmelt, with the heaviest preci- event. pitation reported in the mountains. Rainfall continued at a moderate rate for ' nearly four days. Total precipitation for the storm amounted to 7.60 inches at In Boulder, floodwaters covered the entire area between Water Street (Canyon Boulder and 9.34 inches at the Boulder Hydroelectric Plant on Boulder Creek ' Boulevard) and University Hill to depths as great as eight feet. Every bridge in located about 3 miles up the canyon from Boulder. Precipitation amounts totalled Boulder and a number of residences were swept away. Other types of damage 8.11 inches at Eldorado Springs and 10.05 inches at Gross Reservoir on South ' included commercial establishments , public utilities, railroad property, roads Boulder Creek. Peak flooding occurred on the 7th of May at Boulder and Eldorado and streets, and irrigation structures. Many people were trapped in their homes Springs. A peak discharge of 1 ,690 cfs occurred on South Boulder Creek at and had to be rescued. Only one life was lost; this was due, in part, to the Eldorado Springs. Large portions of the floodplain were inundated below the flood's slow onset. confluence of South Boulder and Boulder Creeks. ' In the valley, downstream from Boulder, the floodplain was reported to have been Analysis of gaging records show that floods the size of the May 1969 flood occur inundated to an average width of approximately one mile for several days. on an average of about once every seven years on South Boulder Creek (Reference ' Agricultural damages included loss of livestock, crops, pastures, fences, roads 2) • and deposition of sand and silt on floodplain lands. In addition, considerable 1 5