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<br />Bank Protection - Since localized bank velocities over 8.0 feet per second could occur <br />along the river, protective measures against scour were required. <br /> <br />Interior Drainage - Ponding areas for interior drainage have the capacity to store a 1 hour, <br />25-year frequency storm volume generated over their contributing drainage areas on the landside <br />of the levee. The coincident 25-year flood on the Arkansas River would be 46,500 c.f.s. <br /> <br />PROJECT BENEFITS <br /> <br />The Las Animas Flood Control Project provides 1 OO-year flood protection for the City of <br />Las Animas including property and residents. <br /> <br />Areas and properties in the 100-year floodplain prior to construction of the Project were <br />shown on the U.S. Department of Housing and Urban Development (HUD), Federal Insurance <br />Administration (FIA), Flood Hazard Boundary Map of the City of Las Animas, (Bent County), <br />Colorado, dated December 28, 1973. <br /> <br />Completion of the Project in 1978 modifi,~d thc 1 DO-year floodplains for the Arkansas <br />River and excluded the 100-year flood from the portion of the City in the 100-year flooclplain <br />as shown on the HUD map. As a result the entire corporate limits of the City wl~n' then out of <br />the 100-year floodplain. <br /> <br />FEMA acknowledged the Project's protection in a letter dated June 26,1985, to the City, <br />stating that they had determined that no Special FJ.ood Hazard Areas existed at that time within <br />the corporate limits of the City and that no map would be published. Conversion to the Regular <br />Program of the National Flood Insurance Program was effective July 10, 1985. <br /> <br />POST-PROJECr FLOODED AREAS <br /> <br />The approximate post-project floodplain bOlmdary for the Design Project Flood (143-year <br />flood) in lieu of the 100-year flood is shown on Figure 2 prepared by Board staff. Because of <br />the protection provided by the Project, the pre-project floodplain for the Arkansas River in the <br />vicinity of Las Animas has been modified. The l43,.year flood (and the 100-year flood) is now <br />excluded from the corporate limits of the City of Las Animas. The unincorporated areas to the <br />landside of the Project levee are also protected. <br /> <br />Comparison of the pre-project and post-project floodplains for the Project Design <br />Flood (143-year flood) on Figure 2 emphasizes the significant reduction in floodplain width in <br />the vicinity of Las Animas. The pre-project floodplain width was about 2 and 1/2 miles and the <br />post-project width is about 113 of a mile. At me highway and railway bridges, the width narrows <br />to 830 feet and 858 feet respectively. The importance of a clear floodway channel and well <br />maintained levees in this reach cannot be owr emphasized. <br /> <br />10 <br />