The Slab Creek reach begins with several class IV+ rapids that are within sight of the put-in. The river has a very continuous nature for the next four miles. Many of the rapids are long and require good class IV skills. Mosquito Road Bridge at river mile 3.6 provides alternate access options. The most significant rapid on the run, class V Motherlode Falls, occurs shortly after the bridge.
The gradient eases after this point and the run becomes class II/III in nature. There also is more vegetation, primarily Alders, in the river channel in the lower section. Rock Creek enters on river right at river mile 6.5. The Rock Creek Power House could provide a potential put-in providing access to the class II/III section when SMUD completes a future downstream take-out.
Put in: From Highway 50 in Placerville, take the Schnell School road exit and go north to Carson Rd. till N. Canyon road. Follow N. Canyon Road to Slab Creek Reservoir road and follow that to a junction near the Slab Creek dam. Two gated roads head downhill. One road leads to the right and to the dam. The other leads to the river a short ways below the dam. Unless we can arrange otherwise, parking will be in the turnouts along the road above the USFS gates. The area by the gates must be kept clear as a turn around. Carry boats 3/10s of a mile down to the river. This will be the site of the future improved put-in.
Take out: In the interim of a new Slab Creek Take-Out to be constructed by SMUD, the Rock Creek Powerhouse located on the north side of the river at mile 6.5 will be the public take-out. From Highway 193 in Placerville go east 6 miles on Rock Creek Road. The entrance to the powerhouse will be the second road on the right after you cross over Rock Creek. The gate will be open during scheduled recreational releases by SMUD and limited parking is available by the powerhouse. The gate will be closed all other times but public access to the river is still allowed. BLM has made special arrangements for parking during recreational releases and we ask all boaters to respect the resource or it can be closed to our parking use. Please DO NOT BLOCK THE GATE.
Mosquito Road Bridge is an alternate take out allows boating the steepest few miles while avoiding Morthelode Falls and the easier water below. Unfortunately there only 3 to 5 parking spaces at this bridge. Make sure the bridge stays clear. There are some parking options further away.
From a rafting perspective River Runners President, John Kosakowsky wrote this excerpt from “Slab Creek: The Run That Time Forgot”:
I logged 8 trips on Slab Creek in December and January (some friends of mine rafted it 20 times!). The flows varied between 550 and 1600 cfs. At the low end, we R2ed 10 and 12 foot rafts. You can run all of the holes at low flows and are more worried about big rocks in the way than anything else. It’s a beautiful slalom course and it isn’t very pushy which is nice. At flows around 1000 cfs, a 13’ raft is ideal as there are really powerful drops and holes that want to surf your craft. At 1600 cfs it’s fast and powerful. There are at least 3 river wide ledges that have only one weakness to drive through. The lines are blind at times with the waves crashing high into the air. It starts to feel closer to Class V, and I’m sure the swims would feel at least that serious.
Read the full article on the River Runners website –
Jason Bates wrote at boof.cem,,,,,
Thomas M. wrote ot Boof.com
I think medium flows are between 900-1300. The river starts to get more difficult above 1500 and is much more technical the lower it gets like 600-800
I would rate the run class IV+ overall at medium flows with the exception of mother lode falls V which has a sneak rout on the far left and a semi difficult portage on the right. Another option if you want your shuttle shorter and to avoid portaging mother lode is to take out on river left at Mosquito Ridge rd.
Other Information Sources: Upper American River Project main page.Upper American River Project Schematic.pdfChili Bar Reservoir Planning Unit.pdf
Video-2009-by Bryan Burkhardt
A GUIDE TO THE BEST WHITEWATER IN THE STATE OF CALIFORNIA, HOLBEK & STANLEY, 1998
the Mosquito Road Bridge at river mile 3.6 can provide alternate access and also warns of the approach to the hardest section of the river. Below the bridge several rapids get harder, culminating in Motherlode Falls.
Below Mosquito Rd. Bridge, several rapids get progessively harder as they lead towards the biggest rapid on this run. Motherlode Falls is an awkward portage for many boaters. Reportedly there is a sneak line on far river left.
Rock Creek enters on river right at river mile 6.5. The Rock Creek Power House could provide a potential put-in providing access to the class II/III section of Slab Creek when SMUD completes a future downstream take-out. This section is class II/III with one rapid that is potentially class III+.
During the winter and Spring the creek and powerhouse can sometimes deliver enough water into the river to provide boatable flows. Generally though, the additional water will be less than 100 cfs.
4 months ago
by Theresa Simsiman
Comments to El Dorado County DOT re:Mosquito Road Bridge Replacement Project
Dreamflows.com is currently estimating spill into this reach using hourly reservoir elevation data. This information is provided as part of the new settlement with SMUD. Flows can be claculated from Slab Creek Reservoir elevation. To determine the approximate flow, use the following conversion table for the reservoir elevation: 1850.6 = 535 cfs 1850.7 = 650 cfs 1850.8 = 767 cfs 1850.9 = 892 cfs 1851.0 = 1025 cfs1851.1 = 1180 cfs1851.2 = 1310 cfs1851.4 = 1600 cfs1851.7 = 2150 cfs1851.8 = 2340 cfs
1852.1 = 3000 cfs1852.3 = 3400 cfs
1852.4 = 3600 cfs1852.6 = 4075 cfs
South Fork American River Basin Schematic.pdf shows gauges, diversions, dams and powerhouses in the basin.
White Rock Powerhouse receives the water diverted from the river at Slab Creek reservoir. Information and historical flow data is available at USGS 11443460. The maximum diversion capacity appears to be about 3500 cfs. So there should be spills whenever inflows to Slab Creek are greater than 3500 cfs. See flows at Kyburz to get an idea. Also whenever flows at Chili Bar are greater than 3500 cfs, the excess should be flowing in the Slab Creek section.
Rock Creek Powerhouse is a run of the river powerhouse and so does not affect the total inflow from Rock Creek. The combination of flows in the creek and from the powerhouse equal the natural flow of the creek. The powerhouse has a maximum capacity of about 100 cfs, but can only divert when the creek has high flows. Historical information for the Powerhouse is at USGS 11444280 , while data for the creek is available at USGS 11444201.
Spill flows in June of 2010 have been highly variable, up to 2800 cfs over a day and quite erratic during each day. The diurnal variation at Kyburz is about 500 cfs during this same time and must affect the Slab creek pattern, but it is not easily visible in the actual Slab Creek flow pattern. This implies that large and erratic flows are coming down Silver Creek from Union Valley Reservoir and that Camino Powerhouse is also turning on and off erratically. It seems likely that irregular spill pulses traveling down the river bed at a slower rate of speed are interecting with irregular powerhouse flows when they reach Slab Creek.
Real time flow info is not available for Silver Creek, but historical records are available for a number of related gauges in these reaches. Daily records will not show hourly fluctuations but can sometimes give indications that hourly fluctuations occurred. SMUD 15 minute records are needed to see the actual flow patterns in Silver Creek that are affecting the Slab Creek Section.SF American near Kyburz - USGS #114395. Operated by El Dorado Irrigation District, below their diversion.
SF American below Silver Creek-USGS #11442500 was operational from 1969 to 1993.Silver Creek -USGS #11442000, just above the SF American confluence, was operational from 1922 to 1961. This gauge shows pre-dam, natural flows. Silver Creek below Camino - USGS #11441900, shows flows since the construction of the dams and powerhouses. Silver Creek below Junction Dam- USGS #11441800, only operated from 1987 to 1991, and only shows minimum releases from the dam. Spillway flows bypassed this gauge.Camino PH - USGS #11441895, Maximum flow about 1200 cfs, but actual daily average output is highly variable. Probably related to powerhouse turning on and off at different times each day, even during peak runnoff. Jaybird PH - USGS #11441780, Maximum output about 1100 cfs, but actual daily average output is highly variable. Probably related to powerhouse turning on and off at different times each day, even during peak runnoff.
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Slab Creek Dam spilling
Almost at the end of this run
Big hole at the bottom
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Here are the 2019 scheduled recreational releases for hydropower projects American Whitewater negotiated across California.
Photo by Barry Kruse - Pit 1
News Release from the Chief Administrative Office El Dorado County: The County of El Dorado and a coalition comprising American Whitewater, El Dorado County residents and businesses, and other conservation and recreation organizations today announced an agreement assuring continued access to Mosquito Road Bridge aka “The Swinging Bridge” and the South Fork American River. In the Memorandum of Understanding reached on May 9, 2017, the County agreed to allow year-round, unencumbered pedestrian and vehicle access to the South Fork American River at the bridge dawn to dusk unless a closure is required for emergencies or maintenance.
Recently, the Sacramento Municipal Utility District (SMUD) made an unexpected move to advocate for policies that would undermine environmental protections in the Clean Water Act and the Federal Power Act. American Whitewater worked with SMUD and other stakeholders in negotiating a settlement agreement for the Upper American River Hydroelectric Project (UARP) that was signed by all parties in 2007. The final license for the project was issued in 2014 and included whitewater recreation flows to mitigate the impacts of its project.
Originally built in 1867 the “Swinging Bridge” a.k.a. Mosquito Road Bridge over the South Fork American River has long served as a crucial intersection for avid recreationalists. Yet a Draft Environmental Impact Report (DEIR) recommended removing access at the river and demolishing the bridge once a new $65 million bridge replacement project was completed. Never a debate of either a new Mosquito Road Bridge or the old Swinging Bridge a coalition of recreational stakeholders dared to ask the question why not both?
The California State Water Resources Control Board (SWRCB) recently took a step that sets the stage for increasing recreation flow days for the Class V Slab Creek reach on the South Fork American River in the future. The SWRCB has issued a 401 Certification for Sacramento Municipal Utility District’s new Slab Creek powerhouse and boating flow release valve.
The Sacramento Municipal Utility District (SMUD), American Whitewater and other consultation group members including Jim Eicher, BLM Mother Lode Associate Field Manager, have scheduled the required 2016 recreational flows for South Fork Silver Creek below Ice House Reservoir and the South Fork American River below Slab Creek Dam.
In response to American Whitewater and community advocacy to follow CA Streets & Highway Code 991, the Transportation Division of the El Dorado County Community Development Agency issued an invitation to comment on river access for the Mosquito Bridge Replacement Project. Mosquito Road Bridge is one of two public take-out sites for the South Fork American River below Slab Creek and allows paddlers the option to take-out before the Cls V Motherlode Falls Rapid. Thus it is important for paddlers to take the opportunity to comment with specific river access needs.
Currently, the Transportation Division of El Dorado County in Placerville, CA is in the process of updating a Mosquito Road Bridge Replacement Study that will outline alternatives for a new bridge to be constructed in 2018-2019. Identified as one of the key take-outs for the Class IV-V Slab Creek whitewater reach, American Whitewater believes this is the perfect opportunity to advocate for river access improvements.
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