elicensing
Environmental Work Group
Draft Geomorphology Study Plan 1
SP-G1 Effects of Project Operations on Geomorphic Processes Upstream
of Oroville Dam
Introduction
The effects of dams on upriver geomorphic processes are extensive. These
processes include physical attributes and functions such as channel shape,
channel stability, sediment transport and deposition, and bedload recruitment.
This is caused by the lake, which changes the local base level. As the lake level
changes from day to day and from year to year, the upstream channel responds
with channel aggradation
orand
degradation. This creates a highly dynamic
channel section immediately upstream of the reservoir
,
that can affect riparian
vegetation, fish, aquatic invertebrates, and other resources.
FluctuatingThe altered
base level also affects substrate scour or deposition,
mobilization of sediment, turbidity levels in the lake and its drawdown zone.
.
During winter storms wW
hen lake levels are high, sediment deposits in the upper
reaches of the lake. Sediment is subsequently eroded in the spring and summer
when lake levels are lower, causing large amounts of sediment to move.
In
addition, wave action can erode shorelines during winter storms when lake levels
are high.
High turbidity and sediment movement affects the reservoirs benthic
invertebrates, riparian vegetation, and fish. The sediment deposits sometimes
create fish spawning migration barriers, particularly in small tributaries entering
the lake.
Objective
To determine ongoing project operation effects (primarily seasonal water level
changes) on reservoir sedimentation, landsliding, shoreline erosion, channel
geomorphology, and sediment transport in the Feather River in and above Lake
Oroville. This information will be provided to other studies to be included in their
evaluations of the Oroville Facilities ongoing

effects on riparian resources, water
quality, fish and wildlife. Components of sediment mass balance studies include:
1. Determine sediment conditions and sediment transport requirements.
2. Evaluate sediment sources (including tributaries) and conditions.
3. Map major sediment deposits.
4. Evaluate upstream channel stability.
5. Compare unimpaired and Project-affected sediment regimes.
7. Quantify and characterize sediment volume and grain size variation in Lake
Oroville. Oroville Facilities Relicensing
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Need for Study\ Relationship to Relicensing:
Relicensing participants have identified the altered sediment routing and
reservoir drawdown caused by the Oroville Facilities as

potential project effects
on the river above the lake. The following Project-related structures and
operations can adversely impact sediment transport regimes: diversions,
reservoirs, channels with flow augmentation, tailraces, roads, sluicing/sediment
removal practices, rock drops, surge chamber discharge, spillways/forebay
overflow, and instream structures. These structures can result in the storage of
sediments or the discharge of greater quantities of sediment than would occur
under natural conditions.
The geomorphic investigation will quantify changes that ha
ves
occurred in the
30+ years since the dam was built
to the upper stream system and the area of
the lake
by comparing pre- and post project data. This information will help
address continuing effects to native plant and animal habitats and riparian
resources from hydrologic, channel, and sediment routing changes. These data,
together with other study results, will provide boundary conditions for identifying
and assessing potential management actions.
Study Area:
The study area includes the reservo
i
r
, the fluctuation zone,
and
its the
tributaries
that are influenced by the drawdown of the lake. The effect of the drawdown can
extend to the next salmonid migration barrier upstream of the lake, such as the
Big Bend Dam on the North Fork Feather. On the Middle Fork, the study area
will extend about 3 or 4 miles upstream from the lake. The specifics of the
upstream extent and numbers of tributaries will be based on initial survey results
of the reservoir shoreline exposed during low water conditions.
Methodology and Analysis:
The study methodology consists of five individual tasks.
TASK 1: Obtain and Review Existing Resource Data.
DWR will compile previous work using the State Resources Agency Library and
extensive in-house publications. Hydrologic and cross-section data will be
compiled. A set of base maps and photos will be obtained for plotting the data.
A set of these maps is in the DWR map library. These maps will be used to
quantify pre- and postproject conditions.
Available photography will be compiled for use in charting changes in stream
geo
morphology, vegetation, land use, and other data. The most recent
photography will be ortho-corrected and used as a base for a Geographic Oroville Facilities Relicensing
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Environmental Work Group Draft Study Plan, SPG1
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Information System. If recent photography is not available, it will be obtained
with new flights.
Previous information dealing with the Feather River above Oroville Dam will be
collected. This includes reports on sediment, landslides, watershed attributes,
stream
geo
morphology and others. Historic gauging station data from gages
directly upstream of the lake will be compiled.
Sub-tasks and products under Task 1 include the following: Consult with county, State, and federal agencies, including DFG, CDMG,
USFWS, NMF, USGS, USACE, and USBR. Consult with companies and
private individuals having knowledge of the geology and geomorphic
processes in project area. Perform initial survey of reservoir shoreline noting the location of sediment
deposits, deltas, and bars at or above the water line and relationship to
tributary streams. Review previous work will include compiling data sets, assessing the
adequacy
of the data,

and identifying data gaps. Prepare a general description of the physiographic setting, including maps of
precipitation, geology, soils, topography, vegetation, and other watershed
characteristics upstream of the dam. Most of this information is available and
can be modified from existing DWR and USFS reports. Compile information on large-scale geomorphic processes and disturbances
within the watershed. These include large flood events, volcanic eruptions,
landsliding, and glacial activity. It will also include human-induced events,
such as deforestation, hydraulic mining, urbanization, dam building,
diversions, and others. These events influence reservoir life, sedimentation,
turbidity, storage, and fish. Prepare maps and tables showing the sediment sources in the watershed and
the relative amounts produced by the North, Middle, and South forks. Classify upstream reaches within the sphere of influence of the lake, using
the Rosgen stream classification system. The reaches will be classified using
Rosgens Level I stream typing, then further classified using the Level II
or
higher
classification based on channel
form and
substrate
and form
. The
results of the stream classification and data collection will be presented on the
river atlas and GIS system. Access historic information related to woody debris input to reservoir
TASK 2: Map the Channel Resources in the Tributaries above
Oroville Dam.
DWR will measure the geomorphic channel characteristics of the West Branch,
North Fork, Middle Fork, South Fork and other tributaries, identified during the Oroville Facilities Relicensing
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Environmental Work Group Draft Study Plan, SPG1
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initial survey as being influenced by reservoir-induced backwater effects,
shoreline erosion, and landsliding. Study methodology, computer model
selection, and other parameters will be selected depending on Task 1 findings.
Geomorphic parameters include channel width, depth, cross-section, hydraulic
radius, roughness, large woody debris, gravel bars, islands, and others. Cross-
sections will be surveyed at impacted areas identified
as havingwith
a deleterious
buildup of sediment or excessive erosion. The spacing and level of detail will be
selected based on the magnitude of the impacted area. Some cross-sections will
be surveyed, but intermediate ones may be developed using sonar and GPS
during high lake levels. The end-points will be permanently marked using steel
pipe set in concrete monuments. Each cross-section will have a photo point, and
additional photo points will be established in critical areas.
Pools, riffles, and runs will be mapped. Representative areas at the riffles will be
analyzed using bulk gravel sampling and surface sampling techniques to
determine the surface and substrate quality of trout spawning gravel. Gradation
curves for each riffle will be prepared. These data are particularly important in
evaluating project effects on fish and the riparian community.
Sub-tasks and products under Task 2 include the following: Prepare an aerial photo atlas using recent, rectified aerial photos. These will
be used as a base layer for the GIS system. Establish baselines, locate benchmarks and existing cross-sections, and set
monuments. Survey monuments using GPS. Survey
channel
cross-section
s
using a tagline strung between the endpoints.
Vertical measurements will be taken every ten feet and at topographic break
points. The river portion will be surveyed using a small boat. The roughness
coefficient and bed material size will be estimated for each cross-sec