Oroville Dam: A story of a catastrophe told through photos

Oroville Dam Spillway: The story of a catastrophe in photos Left: 2014, the spillway never kicked into use when the lake level was low due to little rain. Right: 2017, after several weeks of heavy rain, the spillway was used heavily and eroded. less Oroville Dam Spillway: The story of a catastrophe in photos Left: 2014, the spillway never kicked into use when the lake level was low due to little rain. Right: 2017, after several weeks of heavy rain, the ... more Photo: Kelly M. Grow / DWR, Brian Baer / DWR Photo: Kelly M. Grow / DWR, Brian Baer / DWR Image 1 of / 29 Caption Close Oroville Dam: A story of a catastrophe told through photos 1 / 29 Back to Gallery

A gaping hole was discovered in the Oroville Dam main spillway on Feb. 7, 2017, marking the start of a catastrophic situation that unfolded over the course of several days.

As a moisture-packed storm drenched Northern California in early February, a torrent of stormwater and snow melt poured into Lake Oroville. The lake level rose rapidly and Oroville reached full capacity.

To make room in the reservoir and prevent flooding, water was released down the main spillway, a 3,000-foot-long concrete chute that dumps water into the Feather River.

When the crater was discovered on the main spillway, dam operators monitored the situation carefully, reducing the flow to prevent the main spillway from becoming further damaged and inoperable. But they couldn't prevent further erosion and the hole grew into a massive crater measuring more than 300 feet wide and 500 feet long.

As more stormwater flowed down from the mountains, the reservoir continued to swell and on the morning of Feb. 11, it began tumbling over the emergency spillway that had never been used in the 48-year history of the dam.

While the main spillway is lined with concrete and controlled by gates, the auxiliary spillway has no gates and dumps water down an earthen hillside.

Officials noticed erosion and a hole opening below the concrete lip of the emergency spillway on Feb. 12.

Fearing the emergency spillway was in danger of failing and unleashing flooding on towns below, state officials ordered evacuations for at least 188,000 people.

And this is how the nightmare situation at the Oroville Dam started. For the full story and to see the most recent images revealing the severe damage to the spillway, take a look at the gallery above.