8255

• UCREFRP Catalog Number: 8255
• Author: Grams, P. E. and J. C. Schmidt.
• Title: Geomorphology of the Green River in the Eastern Uinta Mountains, Colorado and Utah.
• USFW Year: n.d.
• USFW - Doc Type: Logan, Utah.
• Copyright Material: NO

Grams and Schmidt

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width, and the location of rapids and gravel bars. He argued that the average longitudinal
profile of the river is nearly straight when viewed at the canyon-length scale despite the
pool-drop characteristic of short reaches. Leopold (1969) asserted that the average prof1le
and the semi-regular spacing of rapids, gravel bars, and deep pools - analogous to the
riffle-pool sequence observed in small streams - are indications that the river is in a state
of quasi-equilibrium with respect to material transport and channel morphology. Thus, the
slope of the channel is adjusted to rework and transport the delivered sediment, however
coarse, and the occurrence of rapids and pools is an inherent characteristic of transport
mechanics. Later, in an investigation encompassing several large rivers of the Colorado
Plateau, Graf (1979) found that the spacing of rapids was essentially random, an indication
that local conditions and not internal adjustment mechanisms determined rapid and pool
location. Graf (1979) also determined that debris fans created most of the rapids he
investigated, but did not explain the cause of every rapid.: In contrast, Dolan and others
(1978) and Howard and Dolan (1981) concluded that nearly all of the large rapids and
deep pools in Grand Canyon are located at debris fans at the mouths of tributaries whose
locations are determined by geologic structures such as major faults, folds, and fracture
zones. Tributary processes are therefore highly important in determining the formation of
debris fans and rapids, but geologic structure and geologic history are the ultimate
controls, dictating where tributaries occur.
Canyon-bound rivers have systematic characteristics that are similar over long
reaches. The relationship between channel geometry and bedrock lithology and structure
is the basis for division of the Colorado River in Grand Canyon into morphologically
similar reaches. Schmidt and Graf (1990) identified 11 reaches of similar bedrock
resistence and similar channel geometry based on examination of channel cross sections
surveyed at approximately 1.6-km intervals by Wilson (1986). Smith and Wiele (1995)
statistically analyzed the same set of cross sections and demonstrated that the influence of