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Engineers, Albuquerque District; Mark Stark, U.S. PJmy Corps of Engineers, John Martin Dam Projects Office; Dale W. Cox, Robert Stwalley, and William 1. Long, all directors of the Arkansas River Conservancy District. COMMUNITY CHARACTERISTICS The City of Las Animas occupies a position in the floodplain on the south bank of the Arkansas River in southeastern Colorado. The Purgatorie River joins the Arkansas River about 2 miles downstream of Las Animas. Las Animas' population has been relatively stable and in 1993 was estimated as 2498. The City is surrounded by agricultural land. U.S. Highway 50, State Highway 10], and the Atchison, Topeka, and Santa Fe (AT&SF) Railroad pass through the City. The climate of Las Animas is typical of 1he semiarid plains region east of the Rocky Mountains and is subject to violent thunderstorms resulting in severe flooding. PROBLEMS AND NEEDS Flood Historv Las Animas has suffered many floods from the Arkansas River. The reach of the Arkansas River causing flooding that affects Las Animas lies west and north of the City. This reach extends upstream from the confluence of the Purgatorie River wiIh the Arkansas River to a point about 6 miles west of Las Animas. The an:a subject to flooding is about 1\ miles long from east to west and 2.5 miles wide at Las Animas. The largest flood of record at Las Animas occ;urred in June 1921 with a peak flow of 187,000 c.f.s. The Corps' August 1963, Interim Report on Review Survey For Flood Control, states that nearly the entire city was flooded and water was 4 to 5 feet ckep in places. Subsequent to the 1921 flood the Pueblo Conservancy District constructed a flood control project at Pueblo including a Barrier Dam on the Arkansas River above Pueblo. With the Barrier Dam in operation the June 1921 flood peak would have been 140,000 c.f.s. During th,~ ]970's the Bureau of Reclamation constructed the Pueblo Dam and Reservoir under the sponsorship of the Southeastern Colorado Water Conservancy District The older Pueblo Barrier DiOn was covered by Pueblo Reservoir and thus was breached. With Pueblo Dam and Reservoir in operation, the June 1921 peak would have been reduced to 108,000 c.f.s. The June 1965 peak flow of the Arkansas River at Las Animas was 22,100 c.f.s. This was the sixth highest peak flow of the 1921-1965 period of record. In 1965, much larger inflows occurred downstream of John Martin Dam located 18 river miles downstream of Las Animas. Inflows from south bank tributaries between the darn and Holly near the Colorado-Kansas state line produced unprecedented flow in the Arkansas River between Lamar, Colorado, and Great 2