Documentation of Existing Conditions in the Central Platte Valley

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SECTIONTWO Environmental Setting growth. Currier (1995) did not remeasure sites after the 1995 flood but estimated that 15 to 25 percent of advanced growth was removed by that flood. In a more recent analysis, Currier (1996) examined channel changes in a 45 -mile reach between the J -2 Return and Shelton. In addition to expanding the study area of his previous analysis (Currier 1995), Currier also examined channel changes over a longer period (1984 to 1995) and specifically examined whooping crane habitat within the designated critical habitat reach. Currier (1996) documented an 18.7 percent decline in channel area in the 1984 to 1995 period. The BOR is currently conducting a study of channel changes and channel equilibrium along the Central Platte River. More than 40 cross sections were resurveyed in the fall of 1998, and the data are currently being analyzed. River reaches with greater vegetative encroachment are no longer suitable for either sandhill crane or whooping crane habitat. Small segments of river that retain wide channels, and segments that have been mechanically cleared and maintained free of vegetation by the National Audubon Society and the Trust, are the primary suitable whooping crane habitat remaining on the Platte River (FWS 1997) Early accounts to pre - settlement vegetation suggest that extensive bands of marshes and meadows may have extended along the river's edge (Currier et al. 1985). In 1982, the estimated area of wet meadow had declined to approximately 59 percent of the acreage estimated for 1938. Over the same period, riparian forest and cropland increased by at least 44 to 48 percent (Sidle et al. 1989). Loss of wet meadow habitats is attributed to reduced springtime river flows and ditching for groundwater and surface water drainage. Williams (1978) and Eschner et al. (1983) have described the reduction in spring peak flows that has occurred over the past century. 2.4 HYDROLOGIC BASELINE Analysis being developed by BOR. 2.5 WATER QUALITY Analysis being developed by BOR. 2.6 SEDIMENT Analysis being developed by BOR. 2.7 BOTTOMLAND GRASSLANDS (WET MEADOWS) 2.7.1 Definition In the Platte Valley, the term wet meadow has been commonly used to identify areas of bottomland grasslands that have interspersed wetland channels and swales that are often flooded during the early part of the growing season. These areas may occupy 10 to 50 percent of the area (Currier 1998). According to Currier (1997), "mesic or wet prairies, sedge meadows, emergent IBS derWoodw"Cy* 1w"Servka 68FOD9728600(rl.doc 6/2/1999(9:52 AM)/URSGWCFS2 2 -7