California had suffered through five consecutive years of drought when the storms arrived in early 2017. The parched ground could not absorb the excess precipitation. Lake Oroville, the second largest reservoir in the state, began rising rapidly. Oroville Dam, an earthen embankment dam on the Feather River east of the city of Oroville, serves multiple critical functions: flood control, water storage, hydroelectric power generation through the adjacent Edward Hyatt Powerplant's 819 megawatts of capacity, and water quality improvement for the Sacramento-San Joaquin River Delta. It is a cornerstone of the California State Water Project. As lake levels climbed toward capacity, operators began releasing water through the main spillway.

Damage to the main spillway first appeared on February 7, 2017. A crater opened in the concrete-lined channel, and as water continued to flow, the hole expanded. By February 10, the gaping wound in the spillway had grown large enough that operators faced an impossible choice: continue using the compromised main spillway and risk total failure, or reduce flow and let the lake rise toward the untested emergency spillway. They chose to reduce flow. On February 11, for the first time in the dam's history, water began flowing over the emergency spillway, a concrete weir at the top of a barren hillside that was never designed for sustained use.

The hillside below the emergency spillway began eroding far faster than engineers anticipated. Water carved into the slope, working its way uphill toward the concrete weir in a process called headward erosion. If the erosion undermined the weir, the entire structure could collapse, releasing an uncontrolled torrent into the Feather River. On February 12, with erosion accelerating and no good options remaining, authorities made the decision to evacuate. By February 13, over 180,000 residents of Butte County, Yuba County, and Sutter County had fled their homes. Emergency crews frantically reinforced the emergency spillway with rocks dropped by helicopter while simultaneously increasing flow through the damaged main spillway.

The crisis created cascading problems downstream. Approximately 1.7 million cubic yards of erosion debris clogged the Feather River channel below the dam, blocking releases from the hydroelectric plant and reducing the dam's overall discharge capacity. State workers evacuated over nine million fish and eggs from the hatchery to a satellite facility near Thermalito Afterbay. On February 27, operators shut off flow to the main spillway, allowing crews to begin clearing debris from the river. By then, headward erosion had largely stabilized. The bedrock under the upper spillway proved stronger than the rock washed out from the midsection, and the falling water had excavated a deep plunge pool that dissipated energy and reduced further damage.

Investigations by the Federal Energy Regulatory Commission and an Independent Forensic Team produced a nearly 600-page report in January 2018. Public hearings in May 2017 saw the California Department of Water Resources criticized for ignoring warning signs in the spillway's design. Environmental groups had raised concerns about the emergency spillway as early as 2005. Butte County officials complained that they spent $5.3 million annually on dam-related services with no state compensation. Repairs took over 2 million hours of labor. The main spillway was reconstructed by November 1, 2018. On April 2, 2019, water flowed over the new spillway for the first time, and it held. Periodic maintenance continues through 2025.