Update Oroville Dam: Coordination Improved, Downstream Dredging Explored
Nearly a year after the Oroville dam breach and flooding incident, downstream communities have concerns about river dredging while agencies report improved communication and safety.
Downstream communities still have questions about the Oroville dam’s reliability, along with what can be done about downstream sedimentation buildup in the Feather River, but state agencies abilities to communicate have improved, according to Curt Aikens, general manager of the Yuba County Water Agency (YCWA).
Agency Coordination and Safety Improving
YCWA operates along the Yuba River, but the agency has to track what's happening along the Feather River.
A local delegation, including Yuba City Assemblyman James Gallagher, State Senator Jim Nielsen, Butte County Supervisor Bill Connelly, Oroville Chamber of Commerce President Sandy Linville and Yuba City Economic Growth and Public Affairs Official Darin Gale traveled to Washington, D.C. in November, according to ChicoER, to speak to commissioners at the Federal Energy Regulatory Commission, Federal Emergency Management Agency and the U.S. Army Corps of Engineers about downstream concerns, including sediment buildup in the Feather River system.
The whole system needs to be cleaned up with the same type of emergency response that we saw up at the dam following the spillway incident,” Gallagher said then.
Various agencies coordinate flows at the confluence of both the Yuba and Feather rivers during high-water events, and they also work with other agencies, like the Department of Water Resources, on reservoir releases. According to a GovTech reprint of local news, Aiken indicated coordination has been improved.
As part of YCWA's Forecast-Coordinated Operations program, county agencies interface with the U.S. Army Corps of Engineers, the National Weather Service-River Forecast Center and the DWR Flood Operations Center. The program ensured all agencies were in sync about releases from the New Bullards Bar Reservoir an,d Lake Oroville, so that planning and coordinating operations would reduce downstream flood risks Aikens said.
We would talk every day, look at what was happening, and consider both the short-term and long-term forecasts," he said.
YCWA's New Bullards Bar Dam underwent inspections of its spillway after the Oroville breach and is performing to its design, said Aiken. That effort increased confidence in the safety of New Bullards Bar Dam, and prompted an increase in inspections.
"We are continuing with a more in-depth investigation of the spillway to catch and correct any issues before they arise," Aikens said.
Dredging is a Complex Decision
In their ongoing coverage, the Oroville Series, the Appeal Democrat reported on how dredging could cause more damage to the Yuba, Feather and Sacramento rivers.
Mike Inamine, the executive director of the Sutter Butte Flood Control Agency, said levee damage would be decided by the legal system, but the unusual operation of the spillway resulted in repeated cycles of rapid drawdown of Feather River water levels, which caused bank and slope failures.
But engineering experts and state Department of Water Resources officials believe dredging could cause more damage. YCWA asked MBK Engineers to study dredging the Feather River, and the consultants reported back on December 11th:
“Dredging is not warranted and would not be a cost-effective method of reducing flood risk for the Feather River,” the memo stated. “This is because dredging would not measurably reduce the risk of through- and under-seepage deficiencies throughout the system and the system has adequate freeboard.”
Sediment deposits from both 2016 and 2017 flooding will redeposit regardless of sediment removal, the engineers concluded.
The California Department of Water Resources spokeswoman Erin Mellon said the agency has heard local concerns about sediment buildup and is conducting surveys to understand how the rivers have changed.
“During high-water events, rivers will respond in different typical ways; some sections will scour (creating pools), some sections will experience deposition, and the river will tend to try and meander around a bit,” Mellon said. “These are natural processes and changes in the river system are expected. Trying to correct these naturally occurring changes may cause more harm than good.”
Mellon said if changes threaten infrastructure, the state will act to prevent potential flood damage.
Gallagher said dredging has become increasingly difficult to accomplish, but it is needed for several reasons.
It restricts channel capacity. Just drive over the Nicolaus Bridge and you can see the problem is obvious. Second, the river is less navigable and more dangerous. And the fishing guides tell me the boat ramps are silted in.”
A coalition has been urging the state to remove silt and debris at 33 key locations.