Update Summary, 2011
Riparian and Wetland Complex Monitoring at the Former Gold Ray
Dam Southern Oregon University
March 20, 2012
__________________________________________________
Southern Oregon University (SOU) was one of several organizations contracting with the Rogue Valley
Council of Governments (RVCOG) to monitor the various environmental and social effects of the
removal of Gold Ray Dam on the Rogue River near Central Point, Oregon. Initially, funds for the
monitoring work came from the Open Rivers Initiative Grant from the National Oceanic and
Atmospheric Administration (NOAA). However, the Oregon Watershed Enhancement Board (OWEB)
provided additional funds in 2011 and 2012 to assist in the monitoring effort. SOU was given three
tasks:
1)
2)
3)
Geomorphology and wetted area changes;
Water-quality monitoring and wetland hydraulics; and
Changes in socio-economics associated with the dam removal.
Progress reports and presentations were provided at the end of 2010. Continued progress through 2011
is summarized below.
1.0 Geomorphology and Wetted Area Changes
Methods:
Initial analysis of geomorphic and wetted channel area change was focused on a ‘before and after’
comparison in 2010. To further assess change in the study area, particularly after the first higher flows
in the Rogue, SOU sub-contracted with David Smith Photography, a Portland, Oregon firm specializing in
high resolution aerial orthophotographic imagery to obtain 0.5’ resolution aerial photos during higher
flow conditions, on 6/9/2011. The photos are available at SOU, OSU and at RVCOG. Discharge on the
Rogue River at the nearest upstream USGS gaging station (USGS 14339000 Rogue River at Dodge Bridge,
Near Eagle Point, OR) was 4,020n cfs, in comparison with 2,020 for the 2010 ‘after’ photographs. While
the difference in flow between the 2010 and 2011 imagery precluded direct comparison of surface
areas, particularly of exposed sediment such as bars whose area is dependent of flow conditions, we
were able to show changes is the mainstem channel position, and the condition of wetland sloughs.
These photos were analyzed using ArcMap 9.3.1. The extent of this analysis was the same as previous
work (from the dam location upstream to approximately 500’ upstream of the entrance to Kelley
Slough.) We mapped depositional features (bars and islands) along the main channel of the Rogue
River, and wetted surface area of the main channel, Kelley Slough (North Channel), and Tolo Slough.
These features were all digitized at a similar scale (1:2,000) to ensure consistency in interpretation. A
digital elevation model derived from LIDAR data was used to help define boundaries of wetted area and
geomorphic features, especially where vegetation obscured the boundaries on the photographs. Lidar
data was obtained from River Design Group. These data were collected between April 29th and May 2nd
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2009. We then calculated the area of all digitized features, and outlined the position of the Rogue
channel to show change in channel position, particularly areas of active erosion and deposition.
Results:
Area of exposed sediment was far less and wetted channel area was greater than in the lower flow 2010
imagery, as expected. However, even at the higher flow conditions in the main channel, the slough
continued their trend of becoming dewatered, as the Tolo Slough became completely dry, and the
wetted area of Kelley Slough continued to decline (Figure 1, Table 1).
The location of the channel boundaries of Rogue River immediately upstream of the dam site, and below
the Bear Creek confluence (Figure 1) changed as a result of erosion and deposition between the 2010
and 2011 imagery. Channel change was minimal upstream of Bear Creek, adjacent to the floodplain
ponds (Figure 2). However the field team noticed that a large gravel bar has appeared on the Rogue
Rivers right bank at the entrance to Kelly Slough which might have happened after the 6/09/2011 aerial
flight. The next aerial flight will view the Rogue River discharge at a similar flow to those recorded
previously to minimize the variability of these comprisons.
Figure 1 Analysis of 2011 aerial photographs
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Table 1: Comparison of 2011 results with previous results
2010
2010
Percent
Before (ac) After (ac) change
Exposed sediment - Rogue
mainstem
3.65
13.46 268.77%
Rogue channel - wetted are
54.32
41.71 -23.21%
Kelly Slough - wetted area
15.8
4.49 -71.58%
Tolo Slough - wetted area
5.28
0.58 -89.02%
2011 (ac)
2.71
53.96
3.93
0
Figure 2: Rogue main channel 2010 and 2011
Discussion:
Aerial estimations and hydrologic observations in the primary associated wetlands (Kelley Slough on the
north side of the Rogue River, and Tolo Slough on the south side of the Rogue River) indicate two
different environments. Tolo Slough effectively no longer exists, and appears to have existed only as a
result of the emplacement of Gold Ray Dam (Table 1). Kelley Slough appears to be a more complex –
and viable – wetland system. Although much reduced with respect to open waterways, there appears
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to be hydrologic connection to the Rogue River and the upstream end of the wetlands; there also
appears to be hydrologic recharge from a northern groundwater system (Figure 1).
LIDAR imagery (Figure 3) provides an excellent look at paleo-channel systems within the Kelley Slough
Complex. The present channel of the Rogue River is immediately south of the colored imagery.
Evidence of the location of the late 1800’s course of the Rogue River is found along the north side of the
Slough (location “A”). Historical property records from the 1850’s indicate that the Rogue River existed
in the middle portion of the wetland and may have occupied the channel complex at location “B”.
Piezometer stations in the wetland complex indicate groundwater contributions to the complex in the
northeast portion. The drainage patterns at location “C” may reflect the groundwater contribution.
The emerging picture is one of complex channel shifting and water contribution into the Kelley Slough
area. Although Tolo Slough appears an artifact of damming the Rogue River, Kelley Slough appears to be
a viable wetland even after dam removal.
Figure 3 Paleochannel systems in the wetland complex
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2.0 Field Monitoring and Wetland Hydraulics
Methods:
Six piezometer nests (PNs) consisting of three piezometers each were installed at selected locations
throughout the wetland complex. Each PN is comprised of several features:





Shallow piezometer
Deep piezometer
Shoreline piezometer
Staff gage
Temperature data logger
In addition, pH, electro-conductivity, and water temperature were collected at each piezometer nest
each time they were accessed. The locations are shown on Figure 4 below.
Figure 4, Wetland Complex and Groundwater Study Locations
F2
PN3
PN2
M
PN4
Cold Water
Refugia
Monitoring
F3
PN5
Kelly
Slough
SG7
F1
F4
F1
Flow X Section
PN1
Piezometer Nest Site
PN1
M
Addl. Staff Gage Site
SG7
Former
Gold Ray
Dam
M Addl. Survey Monmt.
M
.
Specific Areas of
Continued Focus
Tolo
Slough
M
M
Bear Creek
Restoration
Monitoring
Results:
PN1 is consistently a hydrologically gaining area that appears to be receiving groundwater (such as from
a seep or spring). The degree of groundwater contribution fluctuates, and has diminished during the
last (Fall 2011) monitoring event. The groundwater is consistently cold (~ 10-11oC) potentially providing
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coldwater refugia for fish. However the wetland water at PN1 is not in direct (open water) connection
with the adjacent Rogue River.
PN2 went dry by summer 2010, however was re-hydrated the following spring 2011 showing slight
gaining conditions suggesting that the water in this part of the slough is seasonal from spring runoff and
shallow infiltration.
Thus far, PN3 has remained saturated, though is consistently looses to (contributes to) groundwater.
The area near PN4 appears to also fluctuate seasonally, both dry vs. wet conditions, and gaining/losing
to groundwater.
Both of the areas nearest the former dam (PN5 in Kelly slough and PN6 in Tolo Slough) have
consistently lost water to the groundwater table prior to dam removal, and slowly went dry after the
dam was removed. Neither area has re-hydrated.
The pH in the wetland complex is markedly different (lower) than the pH in the adjacent Rogue River.
Discussion:
Not surprisingly, a significant portion of the open-water wetland areas of Kelly Slough and Tolo Slough
have been drained by the dam removal. The areas of both of these sloughs near the former dam
consistently appeared to discharge to groundwater, rather than be recharged by it. However, other
areas of Kelly Slough, notably along the entire northern arm continue to exhibit large wetland complex,
with open-water expanses that increase and decrease in area and depth seasonally. The source of
water in the remaining wetland complex appears to be a combination of seasonal runoff, groundwater,
and periodic inundation from high flow events on the Rogue River. It is still too early to tell if the
riparian and wetland areas above the former Gold Ray Dam have reached a new, post-dam equilibrium.
3.0 Socio-Economic Study
Discussion:
The initial phase of the SOU Socio-economic Study focusing on the baseline conditions existing at the
time of planned dam removal was completed as scheduled. No work was planned during the 2011 time
frame. Critical follow-up surveys, observations, and analyses were proposed and approved for the 2012
funding cycle. The SOU research team including Eva Skuratowicz and Dan Rubenson note that the
follow-up surveys are essential in determining the socio-economic impact of the removal of Gold Ray
Dam and remain very interested in completing the study as planned.
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