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SITE CHARACTERISTICS <br /> iTopographi,and Ceornof7ijic Teatimes <br /> Within Section 29, the area of interest is contained within the primary and secondary <br /> alluvial terraces of St. Vrain Creek. These terraces are elevated from one to tour feet <br /> above the ambient water level of St. Vrain Creek. Within the area surveyed, <br /> microtopographic differences exist which can be identified as relict oxbows or channels <br /> of St. Vrain Creek. The area surveyed also contains the last Chance Ditch and a farm <br /> pond. The Last Chance Ditch flows from the eastern boundary of the area of interest <br /> through the property northwest until it intersects St. Vrain Creek north of the property <br /> boundary. The farm pond was constructed along the western edge of tlic tertiary <br /> alluvial terrace. <br /> The property within Section 28 is elevated approximately ten feet above the secondary <br /> alluvial terrace of St. Vrain Creek. This area can be considered a tertiary alluvial <br /> terrace of the St. Vrain drainage. The southern boundary of the property is the <br /> quaternary alluvial terrace which is further elevated (approximately six feet) above the <br /> tertiary terrace. <br /> VegetaGom <br /> Vegetation within the primary and secondary alluvial terraces of Section 29 can be <br /> broadly categorized as riparian woodland, wet meadow, and upland. The area adjacent <br /> to St. Vrain Creek within the primary alluvial terrace was classified as riparian <br /> woodland. A tall (up to 30 m.) overstory of Populus deltoides (plains cottonwood) is <br /> the dominant vegetation. The understory is low and largely comprised of the cool <br /> season grass Poa pratensis (Kentucky bluegrass). This community is notable in the <br /> absence of a shrub understory, common in riparian woodlands of the Colorado east <br /> slope. <br /> Within the confines of the secondary alluvial terrace, both wet meadow and upland <br /> vegetation communities were identified. Wet meadow vegetation appeared <br /> predominantly in microtopographic swales (relict oxbows), below the embankment of <br /> the farm pond, and along the banks of the last Chance Ditch. Vegetation of the wet <br /> i meadows was characteristic off' hydric conditions. The dominant plants of this <br /> vegetation community include a number of sedge species in the Carex, Cyperus, <br /> Schoenoplectus, and Scirpus genera, as well as the dominant rush species Juncus <br /> arcticus. Several grasses which prefer moist to wet conditions were found, including <br /> Hordeum juhatum (meadow foxtail), and Distichlis spicata (saltgrass). <br /> Upland vegetation was found in topographically elevated areas of the secondary alluvial <br /> terrace. Vegetation within this type was represented by species found in mesic to semi- <br /> xeric conditions. As the entire area had been grazed, many of the species found in the <br /> upland community were introduced or weedy. Clumps of Rosa ark-insana (wild rose) <br /> -2- <br />