8252

• UCREFRP Catalog Number: 8252
• Author: Allred, T. M. and J. C. Schmidt.
• Title: Channel Narrowing of the Green River Near Green River, Utah
• USFW Year: 1999.
• USFW - Doc Type: History, Rates, and Processes of Narrowing.
• Copyright Material: NO

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and Wolman, 1984; Andrews, 1986; Everitt, 1993; Stevens et aI., 1995; Collier

et aI., 1996}, natural climatic change (Schumm, 1969; Graf, 1983; Graf et aI.,
1991; Gellis et ,al., 1991), altered land use (Hadley, 1974; Nadler and Schumm,
1981; Brookes, 1989), and via cyclic erosional and depositional processes

(Patton and Schumm, 1981; Nanson, 1986).

Vegetation, both native and introduced, also has been shown to affect

channel form by stabilizing banks and by increasing bank roughness (Hadley,

1961; Schumm and Lichty, 1963; Smith, 1976; Graf, 1978; Williams and

Wolman, 1984; Friedman et aI., 1996). An increase in roughness can lead to

vertical accretion of sediment during overbank flooding events.

Pizzuto (1994) showed that channel narrowing can occur by a process of

. bench building at lower elevations that follows large-scale flooding and channel

widening. He also demonstrated that the balance between erosion and

deposition is correlated to the annual maximum daily mean discharge, a value

that is constantly changing through time. This finding highlights the continuing

readjustment in channel form and geomorphology, and discounts the

importance of a single dominant channel-forming discharge, or effective

discharge, that is responsible for observed channel form.

Lateral Migration Versus
Vertical Accretion

Flood plains are the dominant geomorphic feature of fluvial systems. In

general, floodplain deposits can be separated into two categories: laterally