7049

• UCREFRP Catalog Number: 7049
• Author: Andrews, E. D.
• Title: Present and Potential Sediment Yields In THe Yampa River Basin, Colorado and Wyoming.
• USFW Year: 1978.
• USFW - Doc Type: \
• Copyright Material: NO

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figure 8, and the respective values were ~lotted against the
computed sediment yields. For this cc)fT,~arisJn, sho\'m in figure
ment yields were adjusted to 1,500 mi2 (3.900 ~m2), in order to
\'Iith the Langbein-Schum:rl (1958) relatio:l.

correspond i ng
10, "J I sed i -
be compatible

The sediment y~elds determined at 13 of the 17 gaging stations are
co~siderably less than the estimates that ~ould have been made using the
Langbein-Schumm (1958) relation, as sho..m in f:gure 10. This discrepancy may
be explained, in part, by recent regional trends tm/ards channel aggradation.
Studies by Leopold, Emmett, and ,>.4,yrick (1;66) and Emmett (19:L4.!have sho','m
that small perenniai and ephemeral ~treG.~1 cnanI1els throughouF the Rocky
Mountain'region-' have been aggrading-'since about 1950; that is, sE:diment is
being stored in~ the.chann.el network. L. I~. Brush .(oral commun., 1377) noted
extensive and rapid aggradation_ ot. SOnl-e st,-e'am channeis tributary to the
Little Snake River durin-g-t:he late 1950's and early 1960's. In contrast,
channel d.egr-~t:on was widespread throughout the region from 1880 to 1950
(Bai ley, 1935; Bryan, 1941; Hack, 1942; Thorn\oJaite and others, 1942; Leopold
and Mtller, 1954; Mi ller and Wendorf,. 1958). The factors that have caused
this regional change are not we1 1 understood. Unfortunately, no sediment
records at gaging stations in t~e Yampa River basin cover the pre- and post-
1950 period sufficiently well to confirm that sediment loads have actual iy
decreased. Only four dai I~ sedinent stations were operated in the Colorado
River basin prior to 1948, and all of these have been affected by the
construction of large reservoirs in the past 30 years.

The data used by Langbein and Schumm (1958) 1n their nationwide study
were collected prior to 1957 and therefore represent primarily a period prior
to observed channel aggradation. Conversely, most of the data used ;n this
investigation for the Yampa River basin have been collected since 1975, and
no data were collected prior to 1950. Thus, the data for the Yampa River
basin represent the period of observed channel aggradation. Therefore, it is
probable that generally smaller sediment yields have occurred for a given
a:Tiount of mean-annual precipitation, as indicated in figure 10. This
decrease in sediment yield probably is due to the storage of sediment in the
channels of small streams throughout the YaIT:pa River basin.

ESTIMATED INCREASE IN SEDIMENT YIELDS DUE TO SURFACE
MINING IN THE YAHPA RIVER BASIN

Large increases in the volune 0f coai ~ined from the Yampa River basin
are anticipated during the next 15 years. Most of the additional production
during the next 15 years will be by sur;ace ~ining (U.S. Department of the
Interior, 1976; Udis and others, 1977). As a result, there \'1; J J be an
increase in land disturbance and probably an increase in the quantity of
sediment supplied to the stream chan~ets draining the surface-mined areas.
The Surface Mining Control and Reclamation Act of 1977 (Public Law 95-87)
requires that surface-mined areas must be reclaimed and revegetated according
to specified standards. During and im~ediately following mining, however,
the hi llslopes wi I I be unvegetated, wi II have no soil, and,in many insta0ces,

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