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<br />,IH <br />!I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />, <br /> <br />II <br /> <br />I <br /> <br />,> <br /> <br />River approximately one-quarter of a mile south of the Moon Creek <br /> <br /> <br />confluence and has a drainage area of about 62 square ai1es. <br /> <br />ENVIRONMENTAL SETTING <br />The flood plain of Rock River is generally underlain by sands and <br />gravels. The topography in the vicinity of Rock Rapids is generally <br />flat to moderately sloping with elevations on the order of 13S0! feet <br />mean sea level (m.s.l.) National Geodetic Vertical Datu. of 1929 (NGVD, <br />1929l. Soils along the Rock River are of the Calco-Spi11co-Dempster <br />Association. Generally, these soils are nearly level to moderately <br />sloping, are moderately fine and medium textured, and are poorly drained <br />to well drained soils. Individual soils types mapped in the study area <br />along the Rock River include Alluvial land, Davis silt loam, Davis loam, <br />Dempster silt loam, and Dickman fine sandy loam. Millington loam is <br />also located in the study area along Moon Creek and Toa Creek. Davis <br />loam, Davis silt loam, Dempster silt loam, and Dickman fine sandy loam <br />area listed as prime farmland soils (U.S. Department of Agriculture <br />(USDAl, 1991). Killington loam is considered a prime farmland soil only <br />in areas protected from flooding or not frequently flooded during the <br />growing season (USDA, 1991l. <br /> <br />According to the Iowa Vater Quality Standards (Chapter 61 of the Iowa <br /> <br /> <br />Administrative Code), the Rock River is designated for Class B (VVl <br /> <br /> <br />Significant Resource, aquatic life uses in the vicinity of Rock Rapids. <br /> <br /> <br />The northwestern region of Iowa has very few streams and is largely <br /> <br /> <br />dependent on lakes for water resources. The Rock River is an exceptional <br /> <br /> <br />stream for northwestern Iowa because it is a relatively high-quality <br /> <br /> <br />stream that supports a relatively diverse fish community. Recreationally <br /> <br /> <br />important species include smallmouth bass (MicroDterus dolomieul and <br /> <br /> <br />channel catfish (Ictalurus Dunctatus). The Rock River contains one of <br /> <br /> <br />the few populations of trout-perch (PercoDsis omiscomavcusl and smallmouth <br /> <br /> <br />bass in western Iowa. The rock strata of the area provides excellent <br /> <br /> <br />habitat for the smallmouth bass. The most serious water quality problems <br /> <br /> <br />in the Rock River basin are related to agricultural nonpoint source <br /> <br />pollutants. habitat quality, and flow stability. <br /> <br />6 <br />