In February 2017, Oroville Dam's main and emergency spillways were significantly damaged, prompting the evacuation of more than 180,000 people living downstream along the Feather River and the relocation of a fish hatchery. Damage to the dam's main spillway appeared on February 7, resulting in its closure as management tried to assess the extent of damage and ways to mitigate further damage. As storms dumped significant precipitation on the area, the lake level rose until it flowed over a concrete weir at the top of the dam's emergency spillway, despite the reopening of the damaged main spillway. As water flowed uncontrolled over the weir, headward erosion of the emergency spillway threatened to undermine and collapse the concrete weir, which could have sent a 30-foot (9 m) wall of water into the Feather River below and flooded communities downstream. A collapse never occurred, but the main spillway suffered significant damage and the bare slope of the emergency spillway was significantly eroded.