River Reach Delineations and Beaver Movement in Grand Teton National Park

This project had two components, with the first component providing a background for the second component. Water resources in Grand Teton National Park (GTNP) are both unregulated and regulated by human management. The Jackson Lake Dam and the ponds scattered across the park influence the flow of water. In the process of managing the water it is important to have knowledge of the different components of the streams through which the water flows. One component of this project was to examine the different segments of the major rivers in GTNP and identify the river forms that are displayed by the different reaches of the Snake River above and below Jackson Lake, Buffalo Fork and Pacific Creek. The river form can be segregated into three main categories; the single channel, the meandering channel and the braided channel (Knighton 1984). The different river forms are part of the overall structural composition of the river and can be used to delineate the segments or reaches of the river. The river continuum concept presented by Vannote et al. (1980) provides a theoretical background upon which to construct the river reach system. In 2007, Nelson (2007) completed a reach system project while investigating the fluvial geomorphology of the Snake River below Jackson Lake Dam (Figure 1.). His 20 river reaches provided a zonation of the river that incorporated a range of geomorphic features. This same type of system can be used throughout the GTNP so that researchers have a common spatial unit designation when referencing portions of the Snake River and its tributaries. Ackers (1988) in his work on alluvial channel hydraulics identified three dimensions of meanders that should be considered; width, depth and slope. He further agreed with Hey (1978) that there are nine factors that define river geometry and that these should be considered as well: average bank full velocity, hydraulic mean depth, maximum bank full depth, slope, wave length of bed forms, their mean height, bank full wetted perimeter, channel sinuousity and arc length of meanders. Nelson’s work (Nelson 2007) added another parameter by including a braiding index into the representation of river reach designations. In a more recent work, the Livers and Wohl (2014) study confirmed Nelson’s approach by comparing reach characteristics between glacial and fluvial process domains using similar reach designation characteristics to determine reach differences.