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from the high mountain peaks to the west. The town's central busi- ness district consists of numerous retail and novelty shops located near the confluence of the Big Thompson and Fall Rivers. Areas along upstream reaches of the Big Thompson and Fall Rivers, and the entire Fish Creek basin within the corporate limits, are largely undeveloped. 2.3 Principal Flood Problems The Town of Estes Park has not frequently been subject to damaging floodflows; however, the flood of 1965 demonstrated the potential for flooding that does exist, particularly in areas where buildings encroach upon the riverbanks. Views of the 1965 flood in Estes Park are shown in Figures 2 through 5. The 1965 flood, which was the most recent, was the result of a combination of heavy rain and rapid snowmelt on a warm day in June. Rainfall depth over a 2-day period was approximately 1.9 inches. The peak in the Big Thompson River near Lake Estes was approximately double the normal flow. The 1965 peak of 1,640 cubic feet per second lcfs) was the most damaging flow in recent history, although flows of this magnitude were also recorded in 1949, 1951, 1953, and 1957. Damage from the 1965 event was the result of continued encroachment upon the river channels and blockage of the Fall River culvert at Elkhorn Avenue that diverted flows through the center of town. On July 15, 1982, the Lawn Lake Dam on the Roaring River failed. According to the Rocky Mountain News, this catastrophic failure sent "a 30-foot wall of water down Roaring River The water swept into Fall River . . . At about 8 A.M., it slammed into resorts perched on the river's banks at the west end of Estes Park." The Lawn Lake Dam failure caused property damage estimated at $20 to $30 million, and the loss of several lives. The flooding from this event was more extensive than that which would be caused by the 500-year flood. Figure 6 shows floodwaters from the dam fail- ure in Estes Park. 2.4 Flood Protection Measures The Town of Estes Park is replacing old bridges with bridges designed to avoid bridge backwater by perching the new bridges above the channel. Floodflows spill from the channel before water rises to the low chord of the bridge. The bridge does not create a backwater; hence, it does not increase the flood hazard. Future replacement of inadequate bridges with these perched bridges will reduce flood potential in some areas. 3.0 ENGINEERING METHODS For the flooding sources studied in detail in the community, standard hydrologic and hydraulic study methods were used to determine the flood hazard data required for this study. Flood events of a magnitude which 4