Chapter 3
Examples of Recent Catastrophic
Hydro-Dam Accidents
3.1 Oroville Dam Spillway Accident
This chapter is similar to Chap. 2, but looks at recent hydro-dams failures and major
incidents.
The Oroville Dam is an earth-fill embankment water dam in the Sierra Nevada
foothills northeast of San Francisco owned and operated by the California Department
of Water Resources (DWR). At 770 ft (235 m) high, it is the tallest dam in the United
States and serves for water supply, hydroelectricity generation and flood control.
The dam impounds Lake Oroville and has a capacity to store more than 4400 million
cubic metres of water. We selected the Oroville case because of its interest, although
Oroville dam is not a tailings dam and the dams itself was not breached.
3.1.1 What Happened
In February 2017, heavy rainfalls required the release of water through the main
flood control spillway. On 7 February 2017, erosion of a large area of concrete and
underlying rock in the main spillway was observed (Fig. 3.1) and discharge rates
were reduced to protect the integrity of the structure. This resulted in water levels
behind the dam rising, due to further heavy rainfalls, to the point that the water
began to be discharged over the crest of the emergency spillway. The emergency
spillway discharge channelized as it flowed across the natural terrain downstream of
the crest structure causing extensive erosion, with some of the erosion areas headcutting aggressively toward the emergency spillway crest structure. At this point, on
11 February, the authorities triggered the evacuation of more than 180,000 people
downstream of Lake Oroville. Two days after the evacuation order, when water levels
© Springer Nature Switzerland AG 2020
F. Oboni and C. Oboni, Tailings Dam Management for the Twenty-First Century,
https://doi.org/10.1007/978-3-030-19447-5_3
23
Examples of Recent Catastrophic
Hydro-Dam Accidents
3.1 Oroville Dam Spillway Accident
This chapter is similar to Chap. 2, but looks at recent hydro-dams failures and major
incidents.
The Oroville Dam is an earth-fill embankment water dam in the Sierra Nevada
foothills northeast of San Francisco owned and operated by the California Department
of Water Resources (DWR). At 770 ft (235 m) high, it is the tallest dam in the United
States and serves for water supply, hydroelectricity generation and flood control.
The dam impounds Lake Oroville and has a capacity to store more than 4400 million
cubic metres of water. We selected the Oroville case because of its interest, although
Oroville dam is not a tailings dam and the dams itself was not breached.
3.1.1 What Happened
In February 2017, heavy rainfalls required the release of water through the main
flood control spillway. On 7 February 2017, erosion of a large area of concrete and
underlying rock in the main spillway was observed (Fig. 3.1) and discharge rates
were reduced to protect the integrity of the structure. This resulted in water levels
behind the dam rising, due to further heavy rainfalls, to the point that the water
began to be discharged over the crest of the emergency spillway. The emergency
spillway discharge channelized as it flowed across the natural terrain downstream of
the crest structure causing extensive erosion, with some of the erosion areas headcutting aggressively toward the emergency spillway crest structure. At this point, on
11 February, the authorities triggered the evacuation of more than 180,000 people
downstream of Lake Oroville. Two days after the evacuation order, when water levels
© Springer Nature Switzerland AG 2020
F. Oboni and C. Oboni, Tailings Dam Management for the Twenty-First Century,
https://doi.org/10.1007/978-3-030-19447-5_3
23