Spatial and Temporal Variation in Hydrologic Change Due to Regulation and Tributary Contributions on the Snake River in Grand Teton National Park WY

Abstract

Channel and floodplain form are primarily determined by the flux of water through a reach and the associated transport of the sediment delivered from the upstream watershed. The dominant paradigm of fluvial geomorphology is that the size of the bankfull channel and the characteristics of the adjacent floodplain are maintained by the current hydrologic and sediment supply regimes (Wolman and Miller, 1960; Andrews, 1980; Leopold, 1994). The linkage among flow regime, sediment supply, and channel and floodplain form is well illustrated on regulated rivers where the flow regime and sediment supply are altered by dams. Bed incision under conditions of sediment deficit has been widely described (Mostafa, 1957; Komura and Simmons, 1967; Galay, 1983; Williams and Wolman, 1984). The longitudinal change from near-dam sediment deficit to sediment surplus further downstream has been described by Andrews (1984) and Grant et al. (2003), although local differences in bed texture, channel organization, and valley confinement affect the magnitude of channel and floodplain change in any specific reach (Lagasse, 1981; Grams and Schmidt, 2002, 2005).