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Where the width of the floodplain in broad, alluvial i . ~!; r:.. '_~. ,~y ~~.!.II PloodpW.. A 777 Tl~Z.LzI i/~~~!L-..L.-' PlDodplaill depr...io.. '~ FI~ure 3.2. . Cross.section of river channel and quality areas that would be inundated during overbank flooding valley reaches averages approximately 3,000 feet; in narrow, canyon-bound reaches, the width averages approximately 500 feet. The quality locations for acquisition of floodplain habitats would be in the broad, alluvial valleys where the productivity of zooplankton as food for larval and juvenile fishes is high (Cooper and Severn 1994 a,b,c,d; Mabey and Schiozawa 1993), The floodplain in the narrow, canyon reaches of Upper \ -~ 6,/ ~Yftr / r.lou'i I N~CUlfOll , ..... rip re 3-3. - CroES-lection of river channel and floodplains in narrow canyon reaches inundated during overbank flooding Basin rivers is relatively unaltered by humans so these areas will not be as high a priority for acquisition. The proposed project will entail acquisition and, where warranted, enhancement of up to 10,000 acres of the most floodable lands within the Upper Basin. The total acreage will include up to 5,750 acres along the Green River; up to 3,500 acres along the Colorado River; and up to 750 acres along the Gunnison River. Acreage values are based on relative differences in habitat availability among the target geographic areas. Although monitoring and evaluation will occur throughout the duration of the project, review and re- evaluation will be conducted upon achieving the target acreage. At that time, if it is determined that additional acreage is needed to achieve and sustain species' recovery, then a new EA will need to be developed. J J I J J I I I I I I I J 1 I J I I I B. Socio-Economic Factors, Mesa County, Colorado, is the most populated of the areas considered in this EA. Most of the people reside in the urban communities, with just over one-third (40,125) in Grand Junction, Garfield County, Colorado, surrounds the city of Rifle, which has a population of approximately 6,000, City of Delta is approximately 4,000 with another 4,000 persons within a 5-mile radius of the city. The population of Delta County, Colorado, is projected to increase approximately 16% by the year 2000. Uintah County, Utah, has the slowest population growth rate within the project area. Its largest city is Vernal with a population of 7,900 persons. Population Growth 2000 1997 o 20 40 60 80 100 120 Population (Units of 1000) Legend . Ulnlllh County, UT . Garfield County, CO . D...\ +a. County, CO II Mesa County, Co As the populations of these areas grow, floodplain areas are converted to cities and towns or farms. They are lost to flooding because of dikes and levees used to safeguard fields and homes that are built within the floodplain. III-2