Feather River flows to rise; concerns aired downriver
The Department of Water Resources plans to use the main flood control spillway in the coming days to lower water elevation levels at Lake Oroville, considerably increasing Feather River flows.
DWR intends to use the spillway ‘"on or around” Friday, it said earlier this week in a press release. The spillway was last used Feb. 27 and has since undergone repairs and reinforcement through rock bolting, application of shotcrete and spalling.
The damaged spillway has the capacity to discharge 40,000 to 50,000 cubic feet per second, which will allow DWR to lower lake levels to a desired height of 835 to 840 feet.
Concern lies further down the Feather River, as some wonder about the waterway’s ability to withstand another sudden fluctuation of water level.
Philip Filter and Brad Foster, farmers with orchards along the Feather River, said DWR’s decision to halt flows from the spillway suddenly last month caused riverbank collapses all along their properties.
With news of the upcoming release, both are concerned about further damage.
“We marked the bare barks and trees to see what happens,” Filter said. “We believe we will lose more ground once the water comes up.”
In certain areas, a minimum of 10 to 20 feet of ground loss would put orchards in danger, said Filter.
Along with continued erosion to unprotected banks, Foster is concerned about material which was pulled into the Feather River and damages it may cause downstream.
DWR advises the public to avoid the river due to the potential for increased outflow.
Outflow increases have been in accordance with state and federal standards and are associated with the spring runoff season and scheduled releases from Oroville facilities, according to DWR spokeswoman Lauren Bisnett.
“DWR will raise the outflows as gradually as possible given the increase of water out of the flood control spillway,” she said. “DWR will use both the Thermalito facilities, and the lowflow channel will help manage increased flows to the river basin.”
Chuck Smith, public information officer for Sutter County, estimates an outflow of 50,000 cfs will raise water levels more than 10 feet on the Feather River. Water levels at the Fifth Street Bridge are at 45 feet, which should not raise water levels to more than 55 feet. Monitoring stage is 65 feet.
“It will raise anxiety because it will escape the riverbed and creep back toward the levees,” Smith said. “But we don’t expect any stress on the levees.”
In Yuba County, various levee districts have analyzed levee performance during last month’s high-water events and the capability to endure increased flows, said Russ Brown, Yuba County public information officer. As for natural riverbanks, Brown said there is not much that can be done.
“We’re hopeful DWR will make the flow increases gradual, which would help our riverbanks and levees handle the rising water,” said Brown. “After that, it’s equally important – perhaps even more important – that future decreases in water releases are also gradual, because that is when there is a greater potential for damages to our shorelines and levees.”
Yuba County’s Office of Emergency Services visited properties impacted along the Feather River and immediately contacted DWR and California’s Office of Emergency Services. Brown said the county is concerned about river fluctuation, but said it is in the unfortunate position of responding to upstream activity.
Gradual outflow increases to the Feather River have been consistent with increased turbine operation at Hyatt Powerplant.
The plant has maintained water releases of roughly 12,900 cfs since the last turbine became operational last week.
DWR has used both the Thermalito Diversion Dam and Thermalito Afterbay River Outlet to meet state environmental outflows to the Feather River since the spillway’s use was halted.
Inflows to Lake Oroville have been between 14,000 to 20,000 cfs, which raised reservoir levels from 862 to 862.6 feet in the last 24 hours. Lake capacity is 901 feet.
Crews have removed 1.2 of 1.7 million cubic yards of debris and sediment from the base of the emergency spillway, clearing the way for increases in outflows.