Documentation of Existing Conditions in the Central Platte Valley

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SECTIONTWO EnvironmeEfti Setting generally sufficient to detect changes since the early 1980s, with the exception of the problems noted below. Periodic updating of the BOR GIS database would be required to monitor future changes. Some problems involved in using existing spatial databases to assess changes since the early 1980s include the following: • The WELUT database only includes a portion of Bridge Segment 12. • The term "wet meadow" appears to have been used to identify all bottomland grasslands in the WELUT database. Specific areas of functional wet meadow are not separated from other bottomland grasslands on the floodplain, and they were not identified at all outside of the floodplain. ' There may be other problems, which will be reported by BOR as it completes the GIS database. However, the current GIS database should provide an adequate baseline for future monitoring of land use and habitat changes. 1 Other than the work of Currier (1982) and Nagel (1995) and studies specific to Mormon Island Crane Meadows and the Rowe Sanctuary, there appears to be limited information on plant community composition, structure, and ecology specific to the study area. The WELUT and BOR GIS databases include only broadscale vegetation classifications, and they are not appropriate for assessing the locations, areas, or changes within more narrowly defined communities. 2.9.2 Platte River Hydrology To be provided by BOR in a subsequent draft. 2.9.3 Bottomland GrasslandsMet Meadows Many of the past studies of habitats along the Platte River have used the term "wet meadow" to , loosely describe a complex of wetlands and bottomland grasslands. It is often not clear in the existing literature whether the habitat values described for wet meadows apply to all bottomland grasslands, only wetlands or areas with open water, or to sites with mixed habitats. This may limit the usefulness of the existing baseline for monitoring future changes, depending on the habitat values being assessed. The existing baseline does not appear to adequately identify the locations of wet meadows (as a wetland type). As mentioned in Section 2.9.1, wet meadows were included with other bottomland grasslands in the WELUT database and may be handled the same way in the BOR database. The NWI maps available for the area are not up to date and may not be accurate. All of the existing spatial data based on air photo interpretation is likely to be affected by the inherent difficulty of separating wet meadows from other bottomland grasslands without detailed field studies. Accurate determination of wet meadows and other wetland types would probably require an on -site wetland delineation using evaluation of vegetation, soils and hydrology. W &V&W Ntadwxd ft* 2-14 68FOD9728600/M.dx 61VI999(9.52AM)/URSGWCFS/2 M