New Bullards Bar Dam

The spillwell gates at New Bullards Bar Dam were opened in February 2019.

In an effort to bring to light the many risks associated with flooding in Yuba County, Yuba Water Agency held a virtual learning session Wednesday on the history of flooding and what the present and future hold.

Speaking during the event were Yuba Water Agency employees Ryan McNally, Tim Truong and John James.

The trio presented an overview of not only the history behind many of the water projects and events in the region’s past, but also a look at what the agency is doing to help prevent major floods from happening in the future.

First to speak was McNally, a water operations project manager for Yuba Water Agency. McNally began his presentation by giving a rundown of the history of flooding in Marysville and Yuba County.

“We are surrounded by three major rivers: The Yuba, the Feather and the Bear rivers,” said McNally. “In a lot of respects our region is defined by these rivers and it can be easy to forget about how productive and flashy they can be, especially when we’re trying to emerge from one of the driest years on record. From a hydrologic perspective, Yuba County is very fortunate to have such a remarkably reliable water supply, however that reliability can and often comes at a cost.”

McNally then pointed out that between the years of 1805 and 1997 there have been more than 30 major flood events in the Sacramento Valley. While natural weather patterns have led to flooding, man-made changes to the area have also had an impact.

“In addition to hydrology, one of the factors that also contributes to the flood risk here in Yuba County include its levees and its historic gold mining legacy,” said McNally. “Our region has an extensive history of hydraulic gold mining in the nearby Sierra Nevada Foothills and this mining literally washed away entire mountainsides and led to large quantities of silt being deposited in the rivers which raised the riverbeds. And in some places, the riverbeds were raised higher than the cities themselves, and that includes the city of Marysville.”

McNally said early settlers in the region used “rudimentary levees” to help combat flooding. He said this made flooding worse because of silt that continued to pour into the rivers and the surrounding infrastructure that was put in place over time.

After major flooding that began on Christmas Eve in 1955, the Yuba Water Agency was created in 1959 as a result of the damage and lack of flood control the region had, McNally said. Because of this and other floods that followed, various Yuba County flood control projects began to take shape to help prevent future catastrophic events.

 

‘Real and tangible efforts’

Truong, chief dam safety engineer for Yuba Water Agency, reiterated that the entire region is impacted by floods. 

He described what led to the construction of New Bullards Bar Dam, which plays a major part in helping to reduce flooding in the county.

“This is a monumental achievement for the county,” said Truong. “ … The dam itself holds almost a million acre feet of water in the reservoir.”

Truong said the agency reserves water in the dam over the winter for flood risk reduction.

“The dam also provides water supply for various irrigation districts around the county as well,” he said.

Besides New Bullards Bar Dam, there have been many facilities the agency has built to help reduce flood risk and generate hydroelectric power. These power stations help produce revenue for the agency which in turn uses that money to invest in Yuba County communities.

“Along with local, state and federal partners, there’s been more than a $600 million investment to reduce flood risk in Yuba County, and it’s paid off,” said McNally. “Today, we’re among the best protected areas in the state. And Yuba Water also continues to pay approximately about $5-and-half million annually in bond debt to cover both the agency and Yuba County’s local cost share for much of the completed levee work.”

McNally said the agency is continuing to help fund projects to protect the area through efforts such as building more levees and other flood risk reduction programs.

“These are all projects that are real and tangible efforts to further reduce the risk of flooding,” he said. “They also represent $25 million the agency has leveraged to raise an additional $500 million in state and federal funding.”

 

A new spillway

James, resource planning manager for Yuba Water Agency, described how the agency along with other groups and organizations views and integrates weather forecasts to help with reservoir operations at New Bullards Bar Dam. He said the highly variable climate in California contributes to Yuba County’s flood risk.

James said “being able to accurately predict atmospheric rivers” is important for implementing programs and knowing what can or should be done with regard to reservoirs.

“Improved atmospheric river forecasts and enhanced operations rules are important process and technology upgrades, however to achieve the full benefit of these strategies it requires the ability to release water ahead of large storm events,” said James. “Yuba Water Agency is planning a new spillway named Atmospheric River Control Spillway or ARC Spillway.”

This new spillway is meant to improve the dam’s operational flexibility, reduce flood risk, enhance dam safety and will strengthen the region’s resilience to climate change. The current spillway is not as efficient because of an “inflexible calendar-based approach,” the agency said.

The ARC Spillway will enable the agency to be more flexible and release water ahead of storms.

“The ARC Spillway has the potential to reduce downstream water level by two to three feet during large storm events, increasing the level of protection between 100 and 300 years,” said James. “In some downstream areas, it’s nearly double the level of protection, again significantly reducing the flood risk.”

James said stage reductions for lower water levels “dramatically reduce the stresses on the levees.” He said the ARC Spillway “would be one of our most significant investments in public safety and climate resilience since the construction of New Bullards Bar Dam and the Yuba River Development Project.”

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