As dam failures and incidents occur both nationally and internationally, there is a pressing need to understand the underlying causes for failure to help minimize such occurrences in the future.  Current information on historical dam incidents is scattered, incomplete, missing, and sometimes misleading – making it difficult for owners and practitioners to easily access meaningful information that could assist them with critical design and operational decisions.  If lessons learned and best practices are not effectively communicated, there is a possibility that poor practices will be repeated and preventable incidents will not be averted.

Presented within DamFailures.org are links to individual case studies as well as lessons learned pages that summarize historical dam incidents and failures and the valuable information gleaned from them.  Each page contains background and description, photographs, videos, best practices, and other resources related to the case study or lessons learned being addressed.  The contents of this webpage encompass a range of failure modes, dam types, and dam safety topics including best practices regarding engineering and design practices, human factors, emergency planning and response, operation and maintenance, and regulatory issues. 

The first new studies of 2020 have been uploaded with more currently being researched. The site now has more than 30 case studies and more than 20 lessons learned, as well as 5 ASDSO webinars that can be viewed free of charge as part of a Cooperating Technical Partnership between FEMA’s National Dam Safety Program and ASDSO.


 

October 2020

Lesson Learned: Extreme floods do occur.

Researcher: Gregory Richards
Reviewers: Amanda Hess and Mike Hand

There is significant historical evidence that extreme floods and even Probable Maximum Flood (PMF) magnitude floods do in fact occur.  Studies of historical storm records and trends have consistently found that extremely rare floods approaching PMF magnitude have occurred, will continue to occur, and may increase in magnitude over time.  The fact that an extreme flood event may not have occurred previously at a given dam or watershed does not diminish the reality that such an event could occur.  Extreme floods such as the PMF do occur, are quantifiable, and their likeliness is predictable.  

It is also true that one of the most common deficiencies identified at existing dams is inadequate spillway capacity.  In light of this information, dam owners, operators, engineers and regulators should recognize that extreme floods can and do occur and take appropriate action to mitigate the risks of such events.   
 

Lesson Learned: High and significant hazard embankment dams should have internal filter and seepage collection systems.

Researcher: Everett Taylor
Reviewer: David Marble

Failure of high and significant hazard dams may result in loss of life, significant property damage, or both.  Because of these consequences, a 2-stage filter and drain system is a critical design feature for embankment dams. A filter and drain system is used to capture and measure seepage, protect against backward erosion (piping) and erosion through cracks, and to protect against internal erosion due to seismic events.

 

Case Study: Front Range Flood (Colorado, 2013)

Researcher: John Batka
Reviewer: Bill McCormick

The September 2013 rainfall that occurred on the Front Range of Colorado was the result of an unusual, late season storm event where warm moisture and upslope winds allowed this regional storm to dump up to 17 inches of rain over a seven day period.  It has been reported (Doeskin, 2014) that this storm ranked in the top three of extreme storms documented in Colorado.  The rain event did not have unusually high rain intensity, but had a long duration and high volume which caused extensive flooding.  By most accounts, the rainfall and flooding occurred simultaneously from Colorado Springs in the south, to Fort Collins in the north and impacted numerous dams at the same time.  This case study provides a time line for the events that occurred and the Colorado Dam Safety Branch’s response to this extreme storm event.


 

September 2020

Lesson Learned: Early Warning Systems can provide real-time information on the health of a dam, conditions during incidents, and advanced warning to evacuate ahead of dam failure flooding.

Researcher: Lee Mauney
Reviewers: Bill Johnstone, Jackie Blumberg, Korey Kadrmas, Bill McCormick, Dan Klein, Dusty Myers, Alon Dominitz and Mike Hand

The detection of abnormal or hazardous conditions is the first step in issuing a more timely and effective warning. Early Warning Systems (EWS) allow owners and emergency response teams to provide advanced warning prior to flooding or to identify incidents that are developing at dams and levees. In addition, an EWS enables proactive action to be taken during the development stage of a potential failure which may provide time to take action to reduce the probability of imminent failure. EWS are especially valuable in situations when visual surveillance is not possible, for remote locations with access challenges, or during times when visual inspections are irregular. EWS installations can function as a non-structural risk mitigation measure until the structure can be improved to current standards. Installations have become much more affordable and reliable during recent years, especially when considering long-term value and reduced labor costs. 

 

Case Study: Swift and Two Medicine Dams (Montana, 1964)

Researcher: Lee Mauney
Reviewers: Dan Osmun, Gene Onacko, Mark Baker and Mike Hand

The second week of June 1964 brought one of the worst natural disasters in Montana’s recorded history. In all, the flooding caused 30 deaths, damages of over $500M (in 2020 dollars), and exceeded many of the peak flow records across the state. Precipitation during the 36-hour storm period, June 8-9, 1964, was recorded at upwards of 16 inches, and caused the most severe floods of record on both sides of the Continental Divide. The area affected by resultant flooding covered an area of nearly 30,000 square miles, or about 20% of the state of Montana. While much of the media coverage of this event focused on flooding in more populated areas like Great Falls and Kalispell, all of the fatalities from the flood occurred on the Blackfeet Indian Reservation, where the Swift and Two Medicine Dams failed. This case study discusses the many lessons to be learned from the tragic events surrounding the 1964 flood, and the consequent failures of these dams.

 

Case Study: Fort Peck Dam (Montana, 1938)

Researcher: Keith A. Ferguson
Reviewer: Laila M. Berre

Beginning at about 1:15 pm on September 22, 1938, the upstream slope of the dam adjacent to the right abutment experienced a large failure as the construction work had progressed to within 20 feet of the final dam crest elevation.  One hundred eighty men were working in the area.  Thirty-four men were injured.  Eight men lost their lives, six of whom were never found and are buried somewhere in the dam.

This case study presents a summary of 1) the efforts to investigate and understand the cause of the failure, and 2) the controversy concerning the root cause evaluation.  The Board of Consultants for the project found that the failure was due to the inadequate shearing resistance of the weathered shale and bentonite seams in the upstream right abutment and dam foundation.  They further indicated that “the extent to which the slide progressed upstream, may have been due, in some degree, to a partial liquefaction of the material in the slide.”



August 2020

Lesson Learned:  A complete and thorough dam record is essential.

Researcher: Mark Baker
Reviewers: Lee Mauney and Mike Hand

Almost all dam owners and regulators have files about their dam(s). Any owner who does not, should start to collect and maintain such records.  Some regulatory agencies such as the  Federal Energy Regulatory Commission (FERC) have defined dam record management requirements. However, it is the author’s experience that dam records tend to be scattered in many different locations, some are not digitized, and some records are poorly organized. Often, if research is performed, valuable dam records come to light which could greatly improve dam safety engineering studies.

One of the biggest challenges in doing comprehensive risk/safety assessments of a dam is to have a complete dam record. Most dam owners have a set of files for their dam. Regulators may have a file as well.  Generally, no one knows what information or reports are missing. Often these files are in different locations. The owner, regulator, and the owner's engineers often have different or unshared files or reports. Some other valuable information about a dam is not in anyone’s files, but may be stored off-site in boxes, libraries, archives, newspapers, or only in people’s memory. Sadly, other information or records are permanently lost to history.  This lesson learned gives guidance on how to perform dam record research that can yield a more complete record that has valuable insight into the safety of a dam.


 

June 2020

Lesson Learned: Dozens of dams can fail or be in danger of failing during a single event (i.e. swarming failures). Dam owners and regulators need to prepare for these types of events.

Researcher: Mark Baker
Reviewers: Mike Hand, Ken Smith, John Moyle, Greg Richards and Lee Mauney

Dam owners and regulators need to prepare for multiple dam failure “swarms.” Since 2006, 145 dams have failed in the United States during multiple dam failure (“swarm”) events such as earthquakes, hurricanes, and major storms. Technical papers written after these events show that state dam safety programs and dam owners are stretched thin responding to these events and there are valuable lessons to be learned. 


 

May 2020

Case Study:  Kinugawa Levee at Joso (Japan, 2015)

Researcher: Paul Risher
Reviewer: Bill Johnstone

Beginning around September 6, 2015, Tropical Storm Etau (Typhoon No. 18) together with Tropical Depression Kilo (Typhoon No. 17) began dropping excessive rainfall across northeast Japan. The interaction of the two systems caused them to stall and concentrate rainfall in a narrow band over the Kinugawa watershed. Some places accumulated over 2 feet of rain in a few days. The steep terrain let loose in mudslides, landslides, and flash floods. Four upstream flood control reservoirs in the watershed all had spillway flows sending a significant flood down the Kinugawa River.

The Kinugawa River is a major tributary of Japan’s most important river, the Tone River. They confluence about 20 miles northeast of Tokyo. On September 10th, the Kinugawa River began to overtop its natural banks in a few places and then around mid-day breached the east bank levee in Joso-shi, Ibaraki Prefecture.  The levee is roughly 12 feet high and breached by overtopping of less than 2 feet. It had also been experiencing some sand boils on the same reach. The breach flow and other out of bank flows combined to inundate an area of over 15 square miles.


 

March 2020

Lesson Learned: Dam failure sites offer an important opportunity for education and memorialization.

Researcher: Lee Mauney
Reviewers: Mark Baker, Mike Hand and Wayne Graham

Dam failure sites are important opportunities to honor victims, educate dam safety professionals, and raise awareness of both the risk posed by dams, as well as the numerous benefits dams provide while highlighting the need for continued public funding of the Nation’s infrastructure. Challenges may exist related to funding, safety, and legal concerns, but a range of options are available to commemorate locations where significant dams have failed, and many successful examples can be toured across the United States. At the same time, there are seminal dam failures sites that have been forgotten or are difficult to locate and visit. When a dam fails, there is often pressure to remove the remains or rebuild the dam in order to expeditiously move beyond the incident. However, in certain cases, memorializing a fai led dam is an opportunity worth pursuing. This lesson learned covers benefits, examples and recommended best practices for commemorating dam failure sites.

 

Thumbnail Photo:Dam failure sites are important opportunities to honor victims, educate dam safety professionals, and raise awareness of both the risk posed by dams, as well as the numerous benefits dams provide while highlighting the need for continued public funding of the Nation’s infrastructure. Challenges may exist related to funding, safety, and legal concerns, but a range of options are available to commemorate locations where significant dams have failed, and many successful examples can be toured across the United States. At the same time, there are seminal dam failures sites that have been forgotten or are difficult to locate and visit. When a dam fails, there is often pressure to remove the remains or rebuild the dam in order to expeditiously move beyond the incident. However, in certain cases, memorializing a fai led dam is an opportunity worth pursuing. This lesson learned covers benefits, examples and recommended best practices for commemorating dam failure sites.