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 are links to individual case studies and '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 content of this website encompasses 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. 

Seven new case studies and two lessons learned have been added in 2022, with more currently being researched. The site now has 50 case studies and more than 30 lessons learned in total. In addition, 5 ASDSO webinars can be viewed free of charge as part of a Cooperating Technical Partnership between FEMA's National Dam Safety Program and ASDSO. 


April 2022

Case Study: Little Deer Creek (Utah, 1963)
Researcher: Everett Taylor
Reviewers: Greg Richards and Mike Hand
Little Deer Creek Dam, located 52 miles east of Salt Lake City, Utah, was intended to capture spring runoff for irrigation use throughout the summer. The dam and reservoir would provide water to the South Kamas – Washington Irrigation Company utilizing the Duchesne Tunnel, a trans-basin diversion. The dam was designed to hold 1,450 acre-feet of water with a height of 75 feet. On the morning of June 16, 1963, during its first filling, the dam failed releasing 1,200 acre-feet of water downstream. The failure cost thousands of dollars in property damage, but more critically, resulted in the lost life of a young boy whose family was camping downstream.

The dam likely failed because of internal erosion at the right abutment, exacerbated by poor construction. The failure is testimony of the need for onsite inspection and testing during construction, monitoring during initial filling, and the vital importance of emergency action plans.

Case Study: Sugar Creek Watershed Dam No. L-44 (Oklahoma, 2007)
Researcher: Gregory Richards
Reviewers: Wade Anderson
In August 2007, tropical depression Erin swept across Oklahoma. In the drainage area above Sugar Creek Watershed Dam No. L-44, it is estimated that over eight inches of rain fell in about six hours causing activation of the earth-cut auxiliary spillway. Flows from the spillway were discharged beyond the toe of the earth embankment but returned after encountering the embankment of County Road 1310 located downstream. This unusual flow condition in combination with failure of the right spillway dike and backwater from debris plugging the culvert under County Road 1310 led to significant erosion of the downstream slope of the dam. Ultimately, the erosion advanced through more than half of the width of the dam embankment crest.  Had spillway flows continued much longer, the dam would have failed due to erosion and instability of the remaining embankment material.  


March 2022

Case Study: Williamsburg Reservoir Dam (Massachusetts, 1874)
Researcher: R. Lee Wooten
Reviewers: Alon Dominitz and William Johnstone
The industrialists who built the factories and the dams along the Mill River in Williamsburg, Massachusetts, were a remarkable group – inventive, hard-working, adaptive, political, and compassionate. They were, by necessity, cooperative in their shared use of the Mill River. However, their human characteristic of Yankee frugality and the physical features of the Mill River valley proved to be the major factors in America's first major dam disaster. On Saturday morning, May 16, 1874, the persistent seepage pressure through the Williamsburg Reservoir Dam and foundation finally caused the steep downstream slope of the dam to slide away, releasing the 2000 acre-feet of stored water down the narrow valley. The water wiped out the valley villages and factories and killed 139 people. If not for the early detection of the pending failure by the dam tender's family and the efforts of several men to warn the downstream communities, the death toll would have been higher by many hundreds. As America's first major dam tragedy, the event drew national attention and was followed by a trial and an American Society of Civil Engineers investigation, both of which found fault with numerous parties – the industrialist owners, the designer, the contractor, the county commissioners, and the Massachusetts legislature.

Case Study: Wivenhoe Dam (Australia, 2011)
Researcher: Seth Thompson
Reviewers: Bill Johnstone, Irfan Alvi, and Mike Hand
Beginning in October 2010, the Brisbane River system in South-East Queensland, Australia, experienced record floods due to a combination of a La Niña year and seasonal monsoons. In January 2011, the largest ever recorded inflows for Wivenhoe and Somerset Dams occurred and their flood control capabilities were tested for the first time. Due to discrepancies in the dams' flood operations manual, the operators were unclear which gated release strategy to employ at Wivenhoe. Even with this confusion, investigations showed that the engineers nearly maximized the dams' flood control capabilities. However, had more clear operational guidance been available, the operators could have engaged a higher release strategy sooner that would have slightly reduced flooding downstream. An investigation into the operators' actions lead to their exoneration of any criminal activity. After nearly a decade, flood victims won a class-action lawsuit against the dam owner for negligence. However, in September 2021, the dam owner won an appeal to the initial ruling. The plaintiffs are currently challenging the appeal through the High Court of Australia. This case study highlights several important topics from the event: 1) the dam operators faced challenging decisions when trying to implement operating orders under extreme flooding conditions; 2) investigations found that the operation manual for Wivenhoe and Somerset Dams was poorly written; and 3) several human factors relating to how the operation manual was written and operations during the flood itself played a significant role in how the event unfolded.

Lesson Learned: Embankment dams and levees are vulnerable to damage from wildlife intrusions and animal impacts.
Researcher: Meghan Walter
Reviewers: Cory Miyamoto and Mike Hand
Earth embankment dams and levees are vulnerable to damage from wildlife intrusions and animal impacts. State dam safety officials and federal agencies agree that animal burrows within dams can cause substantial and costly damage if left unmitigated and are a major concern in the safe operation and maintenance of structures (FEMA, 2005). A study by Bayoumi and Meguid in 2011 found that the annual cost of rodent impacts on earthen structures is over one billion dollars (USD). Animal activity around dams can impact how water moves through and under embankments; it can also undermine structural integrity and cause surface erosion. Regular inspection is a critical part of operating any dam and should consider the impacts of wildlife activity. Safe dam operation includes comprehensive and timely inspection and observation of animal impacts, accurate wildlife identification and mitigation, and appropriate repair and preventive measures.


January 2022

Case Study: Val di Stava Dam (Italy, 1985)
Researcher: Meghan Walter
Reviewers: Mike Hand, John Batka and Charles Cobb
On July 19, 1985, two mine tailings dams in northeastern Italy suddenly and catastrophically failed, killing 268 people and causing €133-150 million in damage. The two embankment dams were constructed in the 1960s as settling basins for waste from a nearby fluoride mine. The dams released approximately 180,000 cubic meters of tailings, burying the downstream villages of Stava and Tesero. 

A combination of physical and human factors led to the collapse of the Val di Stava dams. Both dams were built with heterogenous and liquefiable materials, with the toe of the upper dam resting on the unconsolidated material of the lower basin. According to statements by the design engineer and company hands that worked on constructing the upper basin, the surrounding area was known to be swampy due to numerous springs. Similar hydrology conditions were present at the lower basin. Stability analyses performed during design and construction were inadequate, and warning signs were ignored, leading to the disastrous failure of the dams in 1985. In 1992, 10 people were found guilty of manslaughter for their respective roles in the failure and were sentenced to pay damages. 

Case Study: Santa Clara Dam (Utah, 2012)
Researcher: Everett Taylor
Reviewer: Greg Richards
In September 2012, a series of rainstorms moved across southwestern Utah. On the morning of September 11, a debris basin formed by the Santa Clara Dam filled to an elevation that was 9 to 10 feet below the spillway when the city public services director visited the dam to monitor its performance. Nothing unusual was noted during this visit, and the director left the site to check on conditions in other areas of the city. When he returned 30 minutes later, what he found elicited a completely different response. Water from the reservoir was flowing into rodent burrows through the dam resulting in several concentrated leaks on the downstream face. Internal erosion of the dam by these concentrated seepage points ultimately led to the complete breach and failure of the dam. The released reservoir caused damage to 61 homes, 16 businesses, and city infrastructure. No deaths or injuries were caused by the failure, a credit to the City's public services director for his diligent inspection of the dam and rapid activation of the emergency action plan.

Case Study: Palagnedra Dam (Switzerland, 1978)
Researcher: Johnathon Atkins
Reviewer: Alon Dominitz
Palagnedra Dam is a 72-meter tall, 120-meter long concrete gravity arched dam with a storage volume of 4.8 x106 cubic meters. It was constructed between 1950 and 1952. Palagnedra Dam is located in Switzerland, and its primary purpose is for energy production, providing approximately 40% of the electricity to the surrounding area. Although it was unfortunate that the dam overtopped, it did not fail. The Palagnedra dam incident was very influential in advancing Switzerland's spillway capacity and debris management requirements for all dams. 

Lesson Learned: Downstream of constructed spillway exit channels, spillway outflows can erode and even breach dam embankments and can adversely impact the operation of outlet works.
Researcher: Greg Richards
Reviewers: Paul Schweiger and Amanda Hess
Spillway exit flows can cause damage to or even failure of embankment dams. There have been cases where exit flows that were significantly less than the design flood resulted in near breaching of the dam embankment or significant impairment of dam performance due to unexpected, localized hydraulics. The potential for these adverse hydraulic conditions can sometimes be identified during site visits or by reviewing design drawings and documentation. The application of recent advances in hydraulic modeling and spillway integrity analysis software can also facilitate the identification of these potential failure modes.