7425

• UCREFRP Catalog Number: 7425
• Author: Vandas, S. e. a.
• Title: Dolores River Instream Flow Assessment
• USFW Year: 1990.
• USFW - Doc Type: Project Report.
• Copyright Material: NO

both mid-channel and
tributary bars because of
their potential to affect
the floatability of the
river. Mid-channel bars
r~wtinchannelbrm~
ing, and tributary bars are
responsible for the
fonnation and mmnte-
nance of many of the
river's rapids. Both of
these channel features are
limiting factors for
floating the river espe-
cially during low flows.
Mid-channel bars are
fanned during high flows
when a portion of the
coarse sediment load is
deposited because of
some local channel
condition. The most
common occurrences of
mid-channel bars in the study area are in unconfined
reaches where unstable or easily erodible channel
banks exist, and below tributaries that supply large
sediment loads to the river. Pool areas, such as those
upstream from constrictions in the channel, are also
common locations for bars to form.

Figure 16. Establishment of cottonwood seedlings within historic bank-full
channel, in Lower Dolores River.

Fonn resistance refers to flow resistance caused
by either the channel pattern (e.g., meandering) or by
fluvial channel features that cause irregular channel
geometries such as pools, riffles, and bars. The
elements of fonn resistance serve to dissipate stream
energy by causing large turbulent features such as
eddi~, secondary
currents, or plunge
flows.
Bars can
account for a large
percentage of the
total flow resis-
tance in any given
river reach (Figure
17). Bars may be
classified as point
bars (the inside of
a meander bend),
side bars (or
alternating bars),
mid-channel bars
(exposed riffl~),
transverse bars (or
diagonal bars), and
tributary bars (bars
created by tribu-
tary streams). Of
particular concern
for this study are

Figure 17, Point bar located in lower reach of Dolores River.

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