2010-12-17_REVISION - C1981019 (160)

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In addition to experiencing ideal field conditions during August, the new CIR aerial imagery that was exposed during late September, 2005 while wetland vegetation was still actively growing, but upland vegetation was senescing, was ideal for mapping in this manner. In fact, the accuracy of wetland delineation was significantly improved over "on-the-ground" techniques given the aerial perspective afforded and the highly reflective (bright red signature) wetland vegetation in comparison to the senescing upland vegetation (blue, gray, or tan signature). At the time of sampling perennial stream reaches were noted to include: Wilson Creek, Jubb Creek, and Collom Creek (including a majority of the East Fork of Collom). All other drainages were observed to be intermittent or ephemeral. It's possible that the upper portions of the main stem of Jubb Creek and Collom Creek are intermittent in most years as elevated moisture in 2005 may have led to an extension of annual flows. Perennial reaches generally exhibited a defined bed and bank and as such classify as a WUS, although some areas (especially Jubb Creek and lower Collom Creek) routinely exhibited a grass- lined channel that facilitates classification of the watercourse as a wetland rather than WUS. The wetlands along the project area stream courses are typical of Colorado mountain valley wetlands ranging from moist and wet meadows (within alluvial deposition areas) to heavily vegetated herbaceous strips (along stream banks). These wetlands are typically heavily vegetated herbaceous meadows to moist meadow communities because they receive moisture from lateral subirrigation along the stream channel. On occasion, wetlands developing along the margins of older more stable stock tanks exhibit emergent wetland communities. The majority of the wetlands within the project area occur over a rather broad continuum, especially lower in the watershed where stream courses flow over (or more typically have excised into) alluvial / colluvial floodplains. It is in these lower areas where the six larger wetlands were observed. It appears that most of these larger wetland areas receive their primary maintenance water from perched groundwater discharge in the form of seeps and springs located along the margins of the alluvium / colluvium, but also from subirrigation due to the porous soil materials (sands and gravels) underlying the surface soils as well as run-on from the side slopes and flood flows escaping the confines of active channels. In most circumstances, sufficient moisture was observed to be delivered to these wetlands because areas of standing water were readily apparent. To the contrary, one of these six larger wetland areas (Wetland #4) located in the East Fork of Jubb Creek just above the confluence with the West Fork, is in a state of transition to upland. It appears that primary hydrology must have come as saturation of alluvial materials and subirrigation from flood flows. However, given stock tank development upgradient • MUD,R CRZMK c UATMs, INC. Page 39 2005 Collom Vegetation Survey