Submitted By David Vaughn
Professor of Practice, Clemson University
Director of Global Engagement, RESA
Recently, many of us learned about the plight of the earthen Oroville Dam which is tallest earthen or concrete dam in the U.S. at 770 ft.(1), with a concrete spillway, an unarmored earthen emergency spillway that is susceptible to erosion. Nearly 200,000 residents were evacuated due to a potential dam failure and we owe a debt of gratitude to the emergency managers that managed the situation and brought calm to a potentially catastrophic situation. Many news casts focused on the design of the structure which was started in 1961, while others focused on maintenance and upgrade decisions that were made in recent years but what lessons have we learned that will help our communities become more resilient?
We are all familiar with Hurricane Katrina and how on August 29, 2005 over 50 levees failed within days causing billions of dollars of damage and great loss of life. The overtopping of the levees was not the reason for failure but rather that the earthen levees were not hardened with concrete on the community facing slopes. Based upon the lessons learned then, “the U.S. Army Corps of Engineers has now raised the levees back to full height and finished the sections that were never high enough. It has also “hardened” the slopes of many levees with heavy rock or concrete to withstand waves.”(2) These actions have greatly reduced the risk to the city of New Orleans.
An interesting point is that seven weeks after Katrina’s landfall, three environment groups (Friends of the River, the Sierra Club, and the South Yuba Citizens League) acted and filed a motion on October 17, 2005 with Federal Energy Regulatory Commission (FERC), urging federal officials to require that the Oroville dam’s emergency spillway be armored with concrete, rather than remain as an earthen hillside. They said that the dam, built and owned by the state of California, and finished in 1968, did not meet modern safety standards because in the event of extreme rain and flooding, fast-rising water would overwhelm the main concrete spillway, then flow down the emergency spillway, and that could cause heavy erosion that would create flooding for communities downstream, but also could cause a failure, known as “loss of crest control.” The group stated that “A loss of crest control could not only cause additional damage to project lands and facilities but also cause damages and threaten lives in the protected floodplain downstream,”.(3)
FERC rejected that request, however, after the state Department of Water Resources, and the water agencies that would likely have had to pay the bill for the upgrades, said they were unnecessary. Federal officials at the time said that the emergency spillway was designed to handle 350,000 cubic feet per second and the concerns were overblown. “It is important to recognize that during a rare event with the emergency spillway flowing at its design capacity, spillway operations would not affect reservoir control or endanger the dam,” wrote John Onderdonk, a senior civil engineer with FERC, in the Federal Energy Regulatory Commission’s San Francisco Office, in a July 27, 2006, memo to his managers.(3)
In October 2015, South Carolina experienced over 36 dam failures (5) due to a stalled tropical storm and within one year 25 additional dam failures were experienced due to Hurricane Matthew in 2016 (6). One of the disservices that occurred was when the stalled tropical storm of 2015 was classified as a 1,000-year event, which mortified several of my colleagues as it diminishes the reality that extreme events happen every year and that we need to plan accordingly.
Too many times when bad things happen we get to classify these as acts of God or as a black swan event. “The theory of black swan events is a metaphor that describes an event that comes as a surprise, has a major effect, and is often inappropriately rationalized after the fact with the benefit of hindsight.” (4) But we have experienced these failures before, they are not black swan events, therefore, we can model the effects of extreme events, understand the impacts, and mitigate vulnerabilities.
The reality is that California has experienced an incredibly wet winter with it being on track to be the wettest on record in California. The snowpack in the northern Sierra Nevada is 224 percent of normal which is compounded by increase temperatures that threatens to melt the snowpack.(7) Based upon the current trend, this year will be the wettest season since 1982 only 35 years ago, and the Oroville Dam was dedicated in 1968 only 49 years ago.
Research suggests that the increase in frequency and magnitude of weather-related events is tied to climate change (whether it be a natural cycle or human caused). In “Building Safer Cities”, Torben Juul Andersen notes that in the past 30 years, the frequency of disaster events has quadrupled, economic losses have increased by a factor of 2,000 to 3,000, and insurance losses have increased by a factor of 1,000(9). The economic losses have far outweighed economic growth figures for the same period, suggesting that factors beyond the increase in number of events have impacted loss figures.
It is with hope that situations like the Oroville Dam near-failure will foment collaborative discussions about improved design standards which will foster the development of community resilience. Some of the factors that need to be discussed are as follows:
- What is at stake? – Peter Gleick, a water researcher at the Oakland-based Pacific Institute stated that a failure of the spillway could cut into the hillside and release more and more water, leading to a “cascading failure.” (8) This catastrophic event could cause $100s of billions of damages to California’s infrastructure and over a decade of economic impact. Normal and continuous operations of the Oroville Dam is critical to California’s economy and the state should invest in the protection of this resource.
- What is the expected life? – As a rule of thumb, large dam projects like the Oroville Dam seem to have a life expectancy of 50 to 100 years and many of these projects across the country are or will be exceeding their design life span. We need to focus on what measures need to be taken to strengthen our aging infrastructure.
- What is the design threat? – As stated above, the frequency and magnitude of weather-related events has increased dramatically and to some degree it is a moving target. To combat this uncertainty, “the government of the Netherlands has recognized the threat of sea level rise and climate change. Current proposals in Dutch parliament call for upgrades in flood protection. If this proposal passes North Sea flood protection will be upgraded to 1-in-100,000 years status. Such a large commitment is part of the Netherlands’s “Living with Water/We are Here to Stay” campaign.”(10) This is not a recommendation to use a return period of 10,000 years for weather-related events but rather that we need to align the likelihood with the consequences. However, we should recommend that a standard be created that will increase the design threat return periods to 500 or 1,000 years for our highly critical infrastructure.
- Should Failure Mode Analysis be used to detect design flaws? – In 2006, federal officials at the time said that the emergency spillway was designed to handle 350,000 cubic feet per second and the concerns were overblown. However, the reality is that some of the main turbines had to be taken off line, the concrete spillway sustained damage prior to the event which got much worse during the event, and the erosion from the emergency spillway was well beyond expectations. There is enough evidence from Katrina, the SC floods, and the most recent Oroville incident that should dictate the hardening of the emergency spillway slope.
The Oroville Dam incident has highlighted what is at stake, our poor understanding of weather-related events, design flaws, funding short-falls, and to some degree our arrogance as human beings by stating that an event would never happen. The reality is that we have and are learning lessons that need to be acted upon, changes implemented, standards created, and in time our communities will become more resilient.
- Oroville Dam; Wikipedia (https://en.wikipedia.org/wiki/Oroville_Dam)
- “Is New Orleans Safer Today Than When Katrina Hit 10 Years Ago?”; Scientific American; Mark Fischetti; August 27, 2015 (https://www.scientificamerican.com/article/is-new-orleans-safer-today-than-when-katrina-hit-10-years-ago/)
- “Oroville Dam: Feds and state officials ignored warnings 12 years ago”; The Mercury News; Paul Rogers; February 12, 2017 (http://www.mercurynews.com/2017/02/12/oroville-dam-feds-and-state-officials-ignored-warnings-12-years-ago/)
- “Black swan theory”; Wikipedia (https://en.wikipedia.org/wiki/Black_swan_theory)
- National Performance of Dams Program, Stanford University (http://npdp.stanford.edu/2015_SC_Flood_Failures)
- “Dams again failing in South Carolina”; The State; October 13, 2016 (http://www.thestate.com/news/local/article108153527.html)
- “10 things Southern Californians should know about the Oroville Dam crisis” (http://www.scpr.org/news/2017/02/13/69021/10-things-southern-californians-should-know-about/)
- What is the Oroville Dam, and what will happen if the spillway fails?; USA Today; Ian James; February 13, 2017 (http://www.usatoday.com/story/news/nation-now/2017/02/13/what-oroville-dam-and-why-so-terrible-if-fails/97844512/)
- “Building safer cities: the future of disaster risk.”; Kreimer, Alcira, Margaret Arnold, and Anne Carlin; World Bank Publications; 2003.
- “Sea Level Rise and the Future of the Netherlands”; ICE Case Studies; Vanessa McKinney; May 2007 (http://www1.american.edu/ted/ice/dutch-sea.htm)