In February 2017, heavy rainfall damaged Oroville Dam's main and emergency spillways, prompting the evacuation of more than 180,000 people living downstream along the Feather River and the relocation of a fish hatchery.

[5] For flood control purposes, some space in Oroville Reservoir has to be kept dry to capture floodwaters, a practice that has caused controversy at other dams of California over the amounts of water wasted.

[7][8]: 6–9  At the time of the incident, the Oroville Dam Reservoir Regulation Manual had last been updated in 1970 and the discharge charts were based on climatological data and runoff projections that did not account for climate change or significant floods in 1986 and 1997.

[7][9] The Final Report of the Independent Review Board, released 11 months after the crisis, did not cite the outdated manual as a significant factor.

According to FERC engineering guidelines, "Emergency spillways may be used to obtain a high degree of hydrologic safety with minimal additional cost.

"[8]: 18–19  The FERC determined that the emergency spillway structure was compliant with its engineering standards and that the erosion concerns raised by the environmental advocacy groups were overblown.

[17] The headward erosion of the emergency spillway threatened to undermine and collapse the concrete weir, in which case a 30-foot (9 m) wall of water would be sent into the Feather River below and flood communities downstream.

[17] On February 12, 2017, evacuation was ordered for those in low-lying areas along the Feather River Basin in Butte, Yuba and Sutter counties, because of an anticipated failure of the emergency spillway.

A failure of the concrete top of the spillway would allow up to 30 feet (9 m) vertical of Lake Oroville through the gap in an uncontrolled deluge.

[27] On February 13 helicopters began to drop sandbags and large rocks in the area of the now-dry emergency spillway, in order to protect the base from erosion.

[20] Debris was carried downstream and caused damage to the Feather River Fish Hatchery due to high turbidity.

[35][36] On February 27, the flow to the spillway was temporarily shut off, allowing crews to begin removing debris in the river in preparation to restart the power plant.

[39] The Federal Energy Regulatory Commission (FERC) ordered the California Department of Water Resources (DWR) to assemble a team of five independent experts to assess the dam and issue recommendations.

[40] On February 17, 2017, the DWR commissioned an independent Board of Consultants (BOC) to investigate causes, review and comment on repairs to Oroville Dam.

[10][43] The DWR also requested full-time FERC staff to provide immediate oversight, review, and approval of repair plans that would make the dam safe for the 2017–18 flood season.

[46] According to its 2017–18 operations plan, the DWR maintained Lake Oroville at a lower than normal level to reduce the possibility that the spillway would have to be used the following winter.

[47] On April 2, 2019, due to heavy rainfall upstream, the DWR began releasing water over the newly reconstructed spillway at a rate of 8,300 cu ft/s (240 m3/s).