1400 ‎(2)‎

• UCREFRP Catalog Number: 1400
• Author: Simons, D. B., et al., ed.
• Title: Proceedings
• USFW Year: 1980.
• USFW - Doc Type: Workshop on Downstream River Channel Changes Resulting From Diversions or Reservoir Construction.
• Copyright Material: NO

Only two reaches, Lily Park and Box Elder, were to be considered in any
detail. Additional information included excerpts of background material
from Steel et al. (1978). a report by Andrews (1978) on sediment yield,
monthly flow records from the gaging stations, Yampa River near Maybell
and Little Snake River near Lily, for the period 1910-1976 and projected
flows with the two reservoirs for both stations for the period 1927-
1976. Peak flow records, copi es of da ily sediment loads, a coup 1 e of
snowmelt hydrographs, and topographic maps were also furnished.
Particle size distribution for only one sample of bed material. was
provided; it was collected near the Maybell gaging station.

APPROACH

Introductory sessions of the workshop included an overview by D. B.
Simons, a review of ecological concerns with particular attention to
in-channel habitat, by C. B. Stalnaker, and a summary of the character-
istics of each river by R. T. Milhous.

After the preliminary discussions, R. M. Li presented a general
review of the Yampa River problems with a summary of available data and
a careful exposition of the three basic levels of analysis: 1) qualita-
tive involving geomorphic concepts, 2) quantitative involving geomorphic
concepts and basic engineering relationships, and 3) quantitative
involving sophisticated mathematical modeling concepts. He presented
some qualitative assessments and outlined steps leading to a few results
from the second level approach. He concluded by emphasizing the
importance of a field site investigation and of the need for more
complete data before any detailed computational modeling could be under-
taken.

Dr. Li's introduction was followed by the participants'
presentations and informal discussions by the group to finalize concepts
regarding the approach. The level of analysis by the participants
varied from fairly complex computations to qualitative discussions of
the genera 1 geomorphology and of the data needs both for preliminary
assessment and for detailed evaluations.

A number of aerial photographs and slides of the critical reaches
of the ri ver were rev i ewed duri ng the course of the workshop. Most of
the participants plotted the river profile from topographic maps
provided. Consideration of the profile, the topographic maps, slides
and photographs, and the background information led to the following
conclusions regarding the nature of the river.

1. The Yampa River is not an alluvial channel; its slope is
controlled by the bedrock through which it is cutting its
major canyons. Its pattern and behavior are controlled mostly
by geology rather than by the quantity of water and sediment
it is required to convey.

2. The channel has a pool-riffle configuration over much of the
reach considered. Most of the riffles are formed by cobbles
and boulders fed into the channel from steep, mostly ephemeral
tributaries.

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