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All the floods of record on the South Platte River have been the result of snowmelt and heavy rains in the mountain tributaries from the west or intense rains over the eastern tributaries. Topographic effects combined with regional meteorological characteristics have generated a number of high-intensity rainstorms in an area generally to the southwest, resulting in many floods in the community. The 1933 flood in Littleton was the result of heavy rains in the Big Dry Creek and Plum Creek basins to the south and east. In 1965, heavy rains to the southwest, 14 inches in 4 hours near Palmer Lake, were the primary cause of flooding in the South Platte. Lesser amounts of precipitation, 2 to 4 inches, had fallen over the area prior to the deluge near Palmer Lake (References 4 and 7). Flooding problems in the area have not only been the result of rare storm events, but also of improper floodplain development. Visual accounts of floods have noted the debris carried by the floodwater; not only natural debris of trees, rock, and soil, but also items foreign to the floOdplain, such as houses, automobiles, lumber, and butane storage tanks. These items obstruct bridges and culverts, thus flood heights rise and cause more ext~nsive damage. Property not structurally damaged by floodwaters experiences damage and cleanup costs from residual mud, silt deposits, and erosion. Sheetflow occurs within Littleton on the lower reaches of Little's Creek and Slaughterhouse Gulch. In both areas, the limited- capacity storm-sewer systems are inadequate for the larger runoff events. Once the sewer system capacity is exceeded, flooding proceeds downstream to the South Platte River following a multitude of routes along streets and across private property. Photographs of the extreme flood of June 1965 are shown 10 Figures 2, 3, 4, and 5 (Reference 7). 2.4 Flood Protection Measures With the history of major flood damage from the South Platte River and with completion of Cherry Creek Flood Control Reservoir in 1950, the Denver Metropolitan Area saw the need for an additional flood control structure on the South Platte River just downstream of the confluence with Plum Creek. During the 1950's, planning and design for a flood control reservoir was completed for Chatfield Dam. In 1973, final closure of the dam enabled the facility to store main stem and tributary floodwater. All related reservoir improvements were operational by 1976. Chatfield Dam is located approximately 0.5 mile south of Littleton's upstream corporate limits. The reach of the South Platte downstream of Chatfield Dam is still subject to floods from uncontrolled tributary streams entering below the dam. 6