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-::. In 1965, a unique combination of orographic effects and meteoro- logical conditions in the South Platte River Basin c?-used the worst flooding in the region's recorded history. Severe thunderstorms commenced over the headwaters of Plum Creek and Cherry Creek on June 16, and moved northeasterly down the creeks following and augmenting peak flows. More than 14 inches of rain were recorded at Palmer Lake in 4 hours. Overnight, westerly winds moved the storm front to a position over the Kiowa and Bijou Creek Basins where it met with thunderstorms forming just south of Agate. Here 5.25 inches fell in 45 minutes. The net results of these conditions were six persons drowned, two other deaths caused by flood-related activities, and estimated damages of $500 million in the South Platte River Basin, of which $300 million occurred in the Denver area. Scenes of historic floods in Adams County are shown in Figures 2 through 12. 2.4 Flood Protection Measures The first tangible contribution to flood control affecting Adams County streams was made in 1890, when the Castlewood Dam, primarily intended for irrigation storage, was completed by the Denver Land and Water Company on Cherry Creek, 35 miles upstream from Denver in Arapahoe County. The dam, with a storage capacity of approximately 13,000 acre-feet, was mistakenly regarded by many as protection against deluges. In August 1933, the dam burst under pressure of water from severe thunderstorms in the upper Cherry Creek Basin. Flood control measures on Cherry Creek began in 1936 with the comple- tion of the $800,000, 55-foot high Kenwood Dam, 5 miles from south- ; east Denver, near Sullivan, Colorado. Despite security, Kenwood Dam was not regarded as the complete answer to flood control on Cherry Creek; therefore, in 1950, the Cherry Creek Dam was constructed just upstream of Kenwood at a cost of $20 million. The dam, 14,300 feet wide and 140 feet high, now serves Denver as a park and water recreation area as well as a retarding barrier for floods much larger than the event of June 1965. with a history of major flooding on the South Platte River through 1933 and with the culmination of planning, design, and construction of Cherry Creek Reservoir in 1950, the Denver metropolitan area saw an additional need for a flood control structure on the South Platte River just downstream of the Plum Creek confluence. During the 1950s, planning and design for the Chatfield Dam flood control reservoir was completed. At that time, however, funding was not available to initiate and complete construction. Three hundred million dollars in property damages suffered in 1965 flooding cha.nged ~ 6