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constructed west of the mouth of Sylvester Gulch, in a portion of the area identified. <br /> The applicant estimated the area to be approximately 20 acres in size. However, upon <br /> examination of the Division's aerial photographs, the area of possible fill may be <br /> considerably smaller. Also, it has been confirmed by geologic mapping by the <br /> Colorado Geological Survey (Junge, 1978) that the deposits are not of alluvial origin, <br /> rather colluvial-wedge deposits formed by gravity-dominated processes. On the basis <br /> of this information, this area is found not to meet the geomorphic criteria for an <br /> alluvial valley floor. <br /> Another possible location for an alluvial deposit is found within the west branch of <br /> Sylvester Gulch. However, alluvial origin of the deposit is unlikely. The soils are <br /> deep clay Arquistolls which are susceptible to mass movement and are typically found <br /> on side hill locations. The lack of base level control that would favor clay deposits in <br /> this reach of Sylvester Gulch suggests that the valley deposits are of glacial or perhaps <br /> colluvial (mass movement) origin. <br /> The flood irrigation potential of the site is also questionable. Stream flow records <br /> near the mouth of Sylvester Gulch indicate that flow during the drier months of July <br /> and August are not common. Agricultural development would be limited to grasses <br /> and pasture because of the elevation and short growing season. Based on the soils <br /> review and hydrologic characteristics of this site, the Division does not find the west <br /> branch area of Sylvester Gulch to be an alluvial valley floor. <br /> Isolated alluvial deposits are found within the narrow valley of the North Fork of the <br /> Gunnison River upstream from its confluence with Gribble Gulch. All of these <br /> isolated deposits are less than five acres in size. Some of the deposits are above the <br /> 100-year floodplain, are not subject to flood irrigation and are not subirrigated. The <br /> remainder of the deposits are located within the 100-year floodplain and, therefore, <br /> may be subjected to flooding. Also, due to their proximity to the stream and the <br /> presence of willows and cottonwoods, some of these deposits are apparently <br /> subirrigated. All of these subirrigated deposits are too small and too irregular in <br /> shape to support agricultural development. Many of these deposits are simply islands <br /> created by meander cutoffs and are not accessible. The river poses numerous <br /> difficulties for farming these locations, including access, flooding, and changes in <br /> channel location. Due to the inability of these small isolated alluvial deposits to <br /> support agricultural development, the Division finds that no alluvial valley floors exist <br /> within the narrow valley of the North Fork of the Gunnison River upstream from its <br /> confluence with Gribble Gulch. <br /> Other areas of consideration include isolated high terraces along the North Fork of the <br /> Gunnison River. However, the high terraces are probably not of alluvial origin, and <br /> they may actually represent remnants of glacial debris, particularly in light of their <br /> relatively thin, immature soils. A reconnaissance of the areas showed no evidence of <br /> historic or current agricultural activity. These and other high terraces along the North <br /> Fork have a mining/residential land use history dating back to at least 1935. Terrace <br /> 57 <br />