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Massive erosion on California’s Oroville Dam

Spillway canyon demonstrates power of flowing water


Published: 23 March 2017 (GMT+10)

A crisis at California’s Oroville Dam in early 2017 dramatically demonstrated the incredible power of flowing water. The 235-m (770-ft) dam (figure 1) is a 250 km (160 mile) drive north-east of San Francisco in the foothills of the Sierra Nevada. It’s the tallest dam in the US.

Figure 1. Oroville Dam holding back the Feather River and forming Lake Oroville. At 235 m (770 ft) high, it is the tallest dam in the US.

In February 2017, heavy rainfall in the Feather River catchment raised the water level of Lake Oroville, and operators began a routine release of water down the main spillway. As they increased the flow, even though it was well below its maximum capacity, an unusual flow pattern developed.1 On shutting off the water, they discovered the water had ripped large slabs of concrete from the spillway and eroded the underlying rock. The crater extended almost the full width of the spillway (figure 2).

California DWRspillway-damage
Figure 2. Initial damage to spillway from first release of water.
California DWRSpillway-under-high-flow
Figure 3. Spillway under high flow showing water dropping into plunge pool. Some water flows the full length of the spillway and sprays off the end, while the rest flows to the side of the spillway cutting a canyon into the embankment.

Rains persisted and the dam continued to fill. Because of concerns that the auxiliary spillway could fail, operators had no choice but to use the damaged spillway again. The situation was so serious that more than 180,000 people were evacuated at short notice from the valley below the dam.2

As the flow resumed it eroded more concrete and started to gush alongside the spillway down the embankment (figure 3). However, operators continued discharging water for more than two weeks until the lake had reduced to a safe level.3

When they eventually shut off the flow, the immensity of the erosion was astounding (figure 4). Half way down the spillway the water had excavated an enormous plunge pool—140 m (450 ft) wide, 75 m (250 ft) long, and 40 m (130 ft) deep. Beyond that, most of the concrete structure had been washed away.

Alongside the spillway the water had excavated a long, deep canyon into the rock abutment of the main dam. It was 400 m (1,300 ft) long, 120 m (400 ft) wide, and up to 50 m (160 ft) feet deep (figure 4). Except for a few enormous chunks of rock, the canyon was swept clean of debris, which is typical of a canyon formed by large water flows. The sides of the canyon were steep, a tell-tale sign of being eroded recently.

California DWRcanyons-eroded
Figure 4. The enormity of the spillway damage and canyons eroded revealed after the flow was shut off. Notice the huge plunge pool at the end of the intact spillway, and the canyon carved to the side into the rocky abutment. Notice the hard, grey rock at the base of the canyon and the reddish brown altered material above at the surface. Also note the huge pile of eroded rock debris in the channel at the end of the spillway.
California DWRgrey-debris
Figure 5. Eroded grey debris at the end of the spillway. Note the size of the pile compared with the bulldozer and the people on it, as well as the size of the rock boulders on the pile.

As seen in figure 5, the Oroville Dam spillway sits on red-orange weathered material, which is easily eroded. Beneath that is a hard, resistant, fresh, grey-blue, metamorphic rock, called amphibolite.4 It has repeating north-south fractures called foliation (Latin folium, leaf), similar to a book with its pages sitting almost vertically. This rock was originally of undersea volcanic origin but metamorphosed when the Sierra Nevada was uplifted about halfway through Noah’s Flood. This rock is hard and erosion resistant.

Eroded rock debris was washed into a debris pile in the river channel at the bottom of the spillway (figure 4). The material, with an estimated volume of about 1.3 million cubic metres (1.7 million cubic yards), restricted the channel and prevented the hydro power plant from operating. The rock was so hard that, when excavators were scooping up large boulders to load onto trucks, it would create sparks. The rocks were still angular in shape because they had not been transported far enough to round their sharp edges. The water had carried a large volume of finer material downstream.

The massive canyon eroded by water released from Oroville Dam demonstrates how quickly hard rock can be eroded by flowing water. That the canyon was eroded in just 18 days demonstrates that geological processes occur rapidly when the water flows are large. The highest discharge rate was maintained for just four days. Although the flow down the spillway was alarming in its ferocity, it was many thousands of times smaller than the water flows unleashed on the earth during Noah’s Flood. The Oroville Dam crisis gives a tiny glimpse into the sorts of forces at work during the global Flood, which produced continental scale sedimentary deposits and vast canyons quickly when the enormous cataclysm engulfed the earth.

References and notes

  1. Lake Oroville Spillway Incident: Timeline of Major Events February 4–25, California Department of Water Resources, 27 February 2017; water.ca.gov/oroville-spillway/ accessed 17 March 2017. Return to text.
  2. Rodriguez, O.R. and Thompson, D., Officials order evacuation of residents near California dam, The Associated Press, bloomberg.com, 13 February 2017. Return to text.
  3. For four days water discharged at 100,000 ft3 (2,800 m3) per second (ref. 1). For the remainder of the time it was less. Return to text.
  4. Oroville Spillway Geological Survey, March 7 2017, California DWR, youtube.com/watch?v=W7UGPT0vDZQ. Return to text.

Helpful Resources

Readers’ comments

Louis C.
I love Dr Walker's style of stating things as fact such as "This rock was originally of undersea volcanic origin but metamorphosed when the Sierra Nevada was uplifted about halfway through Noah’s Flood." Just like a uniformitarian geologist would spin a story about how a rock layer has formed, e.g. "This layer was formed during the late Triassic period in a shallow lake environment by seasonal deposition." It is, scientifically speaking, on the same level of credibility, except that the facts fits the Flood model much better than the uniformitarian model...
Louis C.
I just love how Dr Walker always states ideas from his creationist geology model with confidence and as fact, just as the uniformitarians would state e.g. "This rock layer was formed during the late Triassic period 220 million years ago in a lake environment." (Not referring to the rocks in the article.) It is actually funny to think that people would attack his ideas as unscientific storytelling while their version clearly also is - only it fits the facts much more poorly. Keep up the good work!
Mark M.
Noah's flood was in Mesopotamia not North America. If he had had access to Google Earth we would be reading a very different picture in Genesis.
Tas Walker
Mark, The Flood was global. Read the account in Genesis and you will see that it was global. And when you look at the geology of the earth you see that it was formed by that global event. Especially in North America. Check the links I gave you and others because you will be amazed at how compelling the evidence for the global Flood is.
Terry W.
I followed this closely, and it is remarkable how much erosion an average flow of 55000 CFS can do in a couple of weeks. Also pay attention to the emergency spillway: the erosion to it was accomplished by a maximum flow of 12600 CFS in just a few hours. You can see it by clicking on Figure 4 and comparing it to Figures 1 and 3.

But I was less keen about the physical situation as I was about the spiritual situation: I knew on Sunday, February 12 that it wasn't going to undercut either spillway. See the Genesis 9:13 feature in Figure 3 visible just to the right of the bypass flow elbow and the end of the service road. I'm using another Oroville rainbow image as a worship slide background at my church. As the crisis wound down on Youtube and other live streams, it was heartbreaking to see trolls declaring that the dam had failed and posting other such nonsense. Since they were acting much like the children of 2 Kings 2:23, I was and still am very concerned for them. Please join me in praying for their salvation.
Wesley V.
After the Great Seattle Fire about 1889, the city cut down Denny Hill and filled a large area of the waterfront using hydraulics.
Robert E.
The un-armoured emergency spillway to the left of the main spillway was the major concern if it had kept raining. That area would have eroded much faster than the main armoured spillway did, and would have breached the actual dam wall. Thank God the rain stopped before that emergency spillway was needed.
Caleb L.
This is a great story! I live just few hours from Oroville and was amazed by the news coverage showing the damaged spillway. I am so glad Dr. Walker did a story covering the Oroville Dam and how it ties in with biblical Flood geology.
Chris C.
The ability of flowing water to do work is astonishing. Years ago, I worked in fish habitat restoration in Northern California; much of our work involved building in-stream habitat improvement structures out of large redwood or Douglas fir logs and boulders, secured with steel cable and epoxy. After a winter of particularly heavy rainfall, similar to this past winter in California, we went to inspect some of these structures. Not only had many of the structures been demolished by high water, but oftentimes the stream morphology had been so profoundly altered that the structure sites themselves could not be recognized, or even located. As amazing as these changes were to us, the flows that produced them were, as Tas Walker observed, orders of magnitude smaller than what happened during the Flood. As CMI scientists have been pointing out for years, many of the earth's topological features can be readily explained by large-scale hydrologic action.
Anthony A.
Glad to see this made it on the site! When this was happening I was thinking some of the exact things about the sheer power of the water flow over the dam and how much more force a global flood would have on the earth. The flood had to of been a truly terrifying experience, and to think that the power of the flood is insignificant compared to God's power is more than humbling.
Bill P.
I've been hoping you guys would do an article about this dam and spillway. This event along with others like Mount St Helen which are tiny compared to The Flood of Noah's day I hope open up the eyes of many who might have some doubt about creation and the flood as historic events that The Word Of God reveals. Keep up the good work guys...

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