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EXECUTIVE SUMMARY This Floodplain Information Report (Report) regarding the City of Las Animas (City), Colorado, was prepared by Colorado Water Cons(,rvation Board (Board) staff in support of Floodplain Resolution Number 94-356.02. 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. The City has suffered many floods from the Arkansas River. The largest flood of record occurrcd in June 1921. The 1965 peak flow was the sixth largest of the 1921-1965 period. Local interests have, with limited finances" sought for many years to provide protection from reoccurring floods on the Arkansas River. A major stumbling block in the quest for flood protection has been the aggradation of the streambed. Aggradation of the Ark,msas River has been and continues to be a major problem from Pueblo to the Colorado-Kansas :;tate line. The U.S. Army Corps of Engineers (Corps) designed and constructed the levees of the Las Animas Flood Control Project (Project) because the flood threat continued to worsen as thc channel continued to aggrade. Construction was completed June 17, 1978. The Project has provided excellent flood control protection for Las Animas but two significant effects of the continuing aggradation are apparent. The first is the reduction of channel capacity in the Arkansas River. The second effect is the reduction of grade for interior drainage outfall channels. The Federal Emergency Management Agency (FEMA) acknowledged the Project's protection in a letter dated June 26, 1985, to the City of Las Animas. FEMA stated in the letter that they had determined that no Special Flood Hazard Areas existed at that time within the corporate limits of the City and that no map would be published. Conversion to the Regular Program of the National Flood Insurance Program was effective July 10, 198:5. This letter essentially rescinded the approximate floodplain map (Flood Hazard Boundary Map) for the City published by the U.S. Department of Housing and Urban Development (HUD) on December 28, 1973. The HUD map showed a significant pOliion of the City as being in the 1 DO-year f100dplain and subject to the risk of flooding. This current Floodplain Information Report documents for the Colorado Water Conservation Board, the modified 100-year floodplain reflecting the benefits of tit<: Project flood control levees and structures near the City. The Projeet excludes tiLe 100-year Hood from the portion of the City formerly in the I DO-year floodplain and now the entire corporate limits of the City are out of the 1 DO-year floodplain. A caution is raised that floods larger th,m the 100-year flood can occur on the Arkansas River and the City may be subject to risks from such floods. Recommendations are made to designate and approve the floodplain information in this Report.