Laserfiche WebLink
Chapter III <br />WATER -FLOWS AND SEDIMENT OF THE PLATTE <br />Rivers can either be classified as straight, meandering, or braided, or varying combinations <br />of the three. A braided river is defined as having multiple channels that flow through shifting <br />sandbars, large seasonal and annual variations in flows, a relatively steep gradient, and abundant <br />bed load from upstream and bank erosion (Gregory and Walling 1973; Richards 1982; Morisawa <br />1968). Before water diversion began in earnest in the 1880s, the central Platte in Nebraska fit this <br />typical definition of a braided river. Early accounts describe the Platte River in Nebraska as very <br />wide, quite shallow, with very large annual peak flows (O'Brien and Currier 1987, p 22; Eschner <br />et al. 1983, p A15). As discussed in chapter II, cranes, waterfowl, Piping Plovers, and Least Terns <br />depend on a braided, wide, shallow river channel and its associated unvegetated sandbars. These <br />characteristics provide effective barriers to disturbance and predation, and provide nesting sites for <br />the plovers and terns and nocturnal roosting sites for Sandhill and Whooping cranes. <br />The wet meadows' adjacent to the Platte provide key nutrients for migrating waterfowl and <br />other waterbirds. Wetland communities, which make up a significant portion of these grasslands, <br />depend on groundwater levels that fluctuate above and below the ground surface (Duever in press; <br />Hurr 1981). Groundwater levels within one mile or so of the river are directly influenced by river <br />flows and vice versa (Hurr 1981). <br />Trends <br />Water development along the Platte has significantly changed the natural character of the <br />river. With peaks and variations in stream flows reduced and enormous amounts of sediment being <br />trapped behind dams, the channel has narrowed and deepened over time. Some reaches of the river <br />have changed from a braided to a fixed meandering channel stabilized by vegetation. Channel <br />width has decreased as much as 90 percent in some places, resulting in the loss of important habitat <br />for cranes and other waterbirds dependent on the river (USFWS 1981, p 4). <br />1 Wet meadows are technically defined as unbroken grasslands on the floodplain. <br />1 <br />