Gold Ray Dam Removal Monitoring Outline – OSU Biological and Ecological Engineering
Summary Narrative:
In concert with work already underway at Savage Rapids, additional monitoring to consider for Gold Ray Dam is outlined
below. This work compliments and will benefit from other monitoring proposed by collaborators on GRD monitoring
(e.g. SOU, Bob Hughes/Amnis Opes, ODFW, RVCOG, USGS etc.).
Monitoring Objective: Investigate the spatial and temporal effects of removing Gold Ray Dam on geomorphology,
habitat and sediment dynamics.
To contribute to broader sciences (river management, ecology, geomorphology), results will be placed within the
context of natural variability and measurement error, and will be compared to scientific consensus on underlying
processes contributing to changes. Spatial extent will include reservoir area and downstream to Savage Rapids (approx.
15 river miles). Downstream sediment sampling locations and densities, described below, will be based on a) mapping of
potential deposition zones through calculations of stream power to transport sediment and statistical power to detect
effects, and b) coordination with other monitoring efforts.
Coordination: Edge of water surveys will be coordinated with SOU during summer low water. OSU will involve SOU
students in mapping and surveying to share information on RTK GPS survey techniques, and SOU students will assist
with OSU field work. We will consult with Amnis Opes regarding river navigability downstream of the dam.
Sediment Investigations
Our expectation is that sand deposition would likely be minimal in the steeper “transport” reach below Gold Ray dam.
We propose a primary study reach with the upper boundary at Valley of the Rogue State Park and continuing down to
the former site of Savage Rapids Dam. (This coincides with the ODFW redd count/carcass survey site ‘Middle A’ (VOR)
from Valley of the Rogue State Park to the town of Rogue River). We will measure longitudinal profile, pool depth and
volume. We will survey existing gravel bars to obtain extents and volumes, and collect surface grain size measurements
(Wolman 1954) along bar margins and on the downstream 1/3 of bars. These areas are of particular interest due to
their importance as spawning areas for spring and fall Chinook salmon, and the risk that gravel interstices could be filled
with sand evacuated from the reservoir. We plan to survey the pool depths and longitudinal profile of the reach directly
below Gold Ray Dam to Valley of the Rogue state park to examine the potential of larger gravels depositing in pools.
While we do not explicitly plan to survey bars and perform surface sediment assessments in this reach, the spatial
extents of the study should remain adaptable to accommodate logistical challenges and allow for familiarization with
the site.
We will survey the reservoir extensively directly after drawdown and during low water each year to determine the
initial sediment volume as well as the volume and spatial extents of sediment evacuated. We will also collect surface
grain size distributions along transects. Reservoir surveys will include the major sloughs (Lower Kelley and Tolo) now
inundated by Gold Ray Dam.
ADDITIONAL INVESTIGATIONS TO BE TARGETED: While not included as part of this proposal, we will target additional
funding to investigate bedload transport in order to develop a more complete and credible sediment budget below Gold
Ray Dam. Gravels (15% of total stored sediment – Elliot and Dittmer 2009) will move exclusively as bedload and sand
(75% to total stored sediment) will move partially as bedload, depending on stream power and local hydraulics. We
would attempt to gather at least 5 samples (Equal Width Increment, Helley Smith 8055 or similar cable deployed
sampler) at a range of applicable discharges. These samples would need to be collected at the nearest possible
downstream bridge crossing, either the railroad bridge at Gold Hill or the Rock Point Bridge.
References
Elliot and Dittmer, 2009. Preliminary Report of the Sediment Study Conducted at Gold Ray Reservoir, Jackson
County, and Oregon
Wolman, M.G., 1954. A method of sampling coarse river bed material. Transactions of the
American Geophysical Union 35(6): 951-956.
Table 1. Summary of proposed monitoring actions
Action
Surface sediment analysis (pebble
counts and bulk samples) along bar
margins downstream and limited
sampling in the reservoir area.
Justification
Downstream sediment transport and
deposition; grain size and intrusion of sands
that influence spawning habitat quality.
Expected Outcomes
-
GPS ground surveys – bars and
reservoir sediments
Sonar and ADCP profiles of channel
and pools
Documentation of the creation of channel
features and habitat complexity in formerly
sediment starved reach Will be used to develop
sediment budget of the removal.
Calculation of holding habitat changes (e.g.
residual pool depth) due to deposition in pools
and slackwater areas downstream of the
removal; Development of longitudinal profile.
-
-
Activities in addition to field investigations:
-
Data processing
Presentations of monitoring progress and findings at appropriate community meetings
Website with data posted in accessible format (example - spatial data library at
http://rivers.bee.oregonstate.edu/ChiloquinDamRemoval.html)
Annual updates
Development of publications/presentations in conjunction with other monitoring groups
Surface grain size
distribution along
salmonid spawning
habitat in bar margins
Description of erosional
processes in reservoir
Change in bar volumes
Yearly volume estimates
of sediment evacuated
from reservoir
Residual pool depths,
widths
Change in pool volumes
Longitudinal profile of
thalweg
Variability in
velocity/depth