7087

• UCREFRP Catalog Number: 7087
• Author: Elliot, J. G., J. E. Kircher and P. V. Guerard.
• Title: Sediment Transport in the Lower Yampa River, Northwestern Colorado.
• USFW Year: 1984.
• USFW - Doc Type: Denver, CO.
• Copyright Material: NO

to substantial alteration of the Yampa River through Dinosaur National Monu-
ment. This study was undertaken to determine the prevailing conditions of
streamflow and sediment discharge through Deerlodge Park, and to estimate the
effect of changes in hydrology or sediment supply on the sediment budget.
The Yampa River drains approximately 8,000 mil in northwestern Colorado
and south-central Wyoming, and is a major component of the upper Colorado
River system (fig. 1). The Little Snake River, a principal tributary, drains
approximately 3,730 mil and joins the Yampa River in Deerlodge Park.
Mean-annual runoff from the Yampa River basin is approximately 1.5 million
acre-ft/yr. Altitudes in the watershed range from 5,065 ft at the river's
mouth to over 12,000 ft in the headwaters in the Park Range. Precipitation
varies f rom 1 es s than 12 i n. /yr i n the western part of the bas i n to over 60
in./yr at higher altitudes along the Continental Divide. Most of the precip-
itation falls on the basin as snow from November through April, although
intense localized thunderstorms occur during the summer months.
Tertiary and Cretaceous sandstones, mudstones, and shales underlie most
of the basin (Tweto, 1979) and are the source of most of the material trans-
ported by the Yampa River in its lower reaches. The Yampa River is entrenched
into Permian and Pennsylvanian sandstones and limestones of the Uinta Mountain
uplift for the last 45 mi of its course; little of the transported sediment is
derived from these formations.
Immediately upstream from the Yampa River Canyon is Deerlodge Park, a
broad valley where the Little Snake River joins the Yampa River. The Yampa
River Canyon was formed in the Uinta Mountain uplift (Hunt, 1969), and it lies
within the boundaries of Dinosaur National Monument. Entering the canyon, the
river gradient steepens and the channel is entrenched in bedrock. Riverbanks
are predominantly bedrock or talus material. Sand, gravel, and cobbles are
found" locally in bars or along banks where the river gradient lessens, or
where the canyon width increases. Mobile sediments periodically are scoured
from the bed and banks and redeposited as floodflows pass through the canyon.
The canyon of the lower Yampa River in Dinosaur National Monument is a
unique feature in the Western United States. With no major dams, and modest
water consumption (approximately 10 percent of annual streamflow, Steele and
others, 1979), the Yampa River, in its lower reaches, retains a relatively
pristine character. As such, the Yampa River in Dinosaur National Monument
offers the visitor a rare opportunity to observe and study the biological and
geomorphological setting of a relatively undisturbed river system. Rnnual
streamflow in the Yampa River has been measured and sediment yields estimated
for prevailing conditions; however, the effects of changes in either of these
two variables previously have not been addressed. The objectives of this
investigation are:
1. To establish the relation between sediment discharge and water
discharge for the Yampa River above the entrance to Yampa
Canyon at Deerlodge Park.
2. To determine the mean annual hydrograph and flew-duration
relation far the prevailing streamflow at Deerlodge Park.
3. To compute the mean annual sediment supply to the Deerlodge
Park reach.
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