• Encourage or require effective state dam safety programs that provide adequate funding, staff, and statutory authorities;
  • Develop emergency action plans for every high hazard dam by 2011;
  • Establish a national funding program and parallel state programs to repair nonfederally owned dams;
  • Include dam failure inundation mapping as part of the National Flood Insurance Program;
  • Educate the public about dam safety risks;
  • Encourage individuals to educate themselves on the location and condition of dams in their area.


Dams provide essential benefits, including drinking water, power generation, flood protection, irrigation, and recreation. They may be publicly owned and operated by federal agencies, states, cities and municipalities or privately owned and operated by businesses and corporations. Typically earth embankments or concrete structures, dams can reach heights of up to 770 feet and store billions of gallons of water. A dam’s “hazard potential” is classified on the basis of the anticipated consequences of failure, not the condition of the dam. The classifications include “high hazard potential” (anticipated loss of life in the case of failure), “significant hazard potential” (anticipated damage to buildings and important infrastructure), and “low hazard potential” (anticipated loss of the dam or damage to the floodplain, but no expected loss of life).

The National Inventory of Dams (NID), which is maintained by the U.S. Army Corps of Engineers (USACE), shows that the number of dams in the U.S. has increased to more than 85,000, but the federal government owns or regulates only 11% of those dams.3,5 Responsibility for ensuring the safety of the rest of the nation’s dams falls to state dam safety programs. Many state dam safety programs do not have sufficient resources, funding, or staff to conduct dam safety inspections, to take appropriate enforcement actions, or to ensure proper construction by reviewing plans and performing construction inspections. For example, Texas has only 7 engineers and an annual budget of $435,000 to regulate more than 7,400 dams.3 That means each inspector is responsible for more than 1,050 dams. Worse still, Alabama does not have a dam safety program despite the fact that there are more than 2,000 dams in the state. And in some states many dams are specifically exempted from inspection by state law. In Missouri there are 740 high hazard potential dams that are exempted because they are less than 35 feet in height. The task for the states is an enormous challenge. (See Table)
While the total number of dams is increasing, the number of high hazard potential dams is also increasing at an alarming rate, now totaling 15,237.3 That represents an increase of more than 3,300 new high hazard potential dams since 2007. This increase is a result of new development below dams, which is dramatically increasing the consequences of failure and resulting in the reclassification of dams. This change in classification requires that significantly greater safety standards be met given the greater consequences of dam failure.

Number of Deficient Dams in United States by Repair Status

year # of deficient dams # of High Hazard deficient dams # of High Hazard repaired dams # of High Hazard Dams needing repair
2001 1,348 488 124 364
2002 1,536 646 163 483
2003 2,004 648 120 528
2004 3,000 979 100 879
2005 3,271 1,367 138 1,229
2006 3,346 1,308 139 1,169
2007 4,095 1,826 83 1,743

SOURCE Association of State Dam Safety Officials

The number of dams determined to be unsafe or deficient has risen from 3,500 in 2005 to 4,095 in 2007.3 Of that number, high hazard potential dams that are also classified as deficient has risen from 1,367 in 2005 to 1,819 in 2007.3 The greatest indicator of the condition of the nation’s dams can be seen in the Table that demonstrates the increase in the number of high hazard dams that need to be repaired compared to the number of completed repairs to high hazard dams, which remains flat.3 The rate of dam repairs is not keeping pace with the increase in the number of high hazard dams that need rehabilitation. The gap between dams needing repair and those actually repaired is growing significantly.
Many dams are determined to be deficient as a result of aging, deterioration, and a lack of maintenance. Often dams are deemed unsafe or deficient as a result of increased scientific and engineering knowledge about large flood events and earthquakes, and the ability to predict a dam’s structural response to such extreme events, which pose a significant safety threat. Many dams were constructed 30 or 40 years ago using the best science and engineering at the time. But as a result of the additional 40 years of historical records and greater abilities to predict increases in loads on dams and the dams’ responses to those events, more dams are being identified as unsafe or deficient.
The National Dam Safety Program (NDSP), which was established by the Water Resource Development Act of 1996, created a national dam safety program administered by the Federal Emergency Management Agency that is designed to provide incentive grants to states and training to encourage research.12 While there have been successes and improvements as a result of the NDSP and stronger state programs, the safety and condition of the nation’s dams have not improved overall. Successes have included modest increases in staffing, budgets, and dam safety inspections in some state programs. The number of Emergency Action Plans (EAPs)—essential plans used in the event of a failure to identify and notify people residing below a dam, and to coordinate their evacuation—has also increased.9 However, the number of high hazard potential dams nationwide that have EAPs remains at a lackluster 50%. Even worse is the fact that many high hazard potential dams are unregulated and uninspected. Approximately 30% of the high hazard potential dams have not been inspected within the last five years (see Figure).
Federal agencies own or regulate a very small percentage of the 85,000 dams in the U.S. but they face significant challenges in terms of oversight.8 As the country’s dams age, downstream development increases, and better engineering methods are developed, more significant rehabilitation will be needed. Examples include the $317 million rehabilitation of Wolf Creek Dam, which is owned by the USACE, and the major improvements to Folsom Dam, which were jointly undertaken by the USACE and the U.S. Bureau of Reclamation at an estimated cost of $1.5 billion through 2019.
In 2009, the Association of State Dam Safety Officials (ASDSO) estimated that the total cost to repair the nation’s dams totaled $50 billion and the needed investment to repair high hazard potential dams totaled $16 billion. These estimates have increased significantly since ASDSO’s 2003 report, when the needed investment for all dams was $36 billion and the needed investment for high hazard potential dams was $10.1 billion.4
The 2009 report noted an additional investment of $12 billion over 10 years will be needed to eliminate the existing backlog of 4,095 deficient dams. That means the number of high hazard potential dams repaired must be increased by 270 dams per year above the number now being repaired, at an additional annual cost of $850 million a year. To address the additional 2,276 deficient—but not high hazard—dams, an additional $335 million per year is required, totaling $3.4 billion over the next 10 years.4
While much progress in identifying the condition of the nation’s dams has been made since the implementation of the NID, the 2008 failure of a dam retaining coal ash from a power plant in Tennessee points out significant gaps in the regulation of dams associated with the power and mining industry at both the federal and state levels. Many states do not have the authority to regulate mining dams, other states only regulate mining dams after the mining operation has stopped, and some states regulate mining dams through departments other than those that administer the dam safety program. At the federal level there are significant differences in regulatory standards between the coal mining industry and the metal/nonmetal industries regarding standards for design, inspection, and the requirements to provide EAPs for high hazard dams.
Number of High Hazard Dams in the United States


Dams are generally not very resilient because few have redundant structures, many have regional impacts, and only 50% of high hazard dams have EAPs.

The U.S. Department of Homeland Security, through the Office of Infrastructure Protection, has started addressing this important issue in collaboration with the dam safety and dam security communities, federal and state agencies, and the entire spectrum of owners and operators. Given the large number of dams and their broad range of resiliency levels, efforts are being made to develop a rational prioritization approach for coordinating protection programs and resiliency enhancements. Important physical and functional characteristics of dams—such as the consequence of failure and loss of critical benefits—are considered the basis for identifying which dams would have the most severe and long lasting impact if service was lost (drinking water, hydropower, flood damage reduction, inland navigation, etc.). By considering the impact on all sectors—public safety, local commerce, service suppliers, etc.—in the risk evaluation process, strategies that target increased resilience and improved security can be effectively identified.


Despite some successes, the overall condition of the nation’s dams has not improved in recent years. This is evidenced by the rising numbers of dams—especially high hazard dams—that are deficient and in need of repair as well as by the limited number of dams that are actually repaired each year. In order to make significant improvements in the nation’s dams—a matter of critical importance to public health, safety and welfare—Congress, the administration, state dam safety programs, and dam owners will have to develop an effective inspection, enforcement and funding strategy to reverse the trend of increasingly deteriorating dam infrastructure.


  1. Association of State Dam Safety Officials. National Dam Safety Program Successes and Challenges (2003)
  2. Association of State Dam Safety Officials. State and Federal Oversight of Dam Safety Must Be Improved (2007)
  3. Association of State Dam Safety Officials. Statistics on Dams and State Safety Regulation (2007)
  4. Association of State Dam Safety Officials. The Cost of Rehabilitating Our Nation’s Dams: A Methodology, Estimate and Funding Mechanisms (2002; rev. ed., 2008)
  5. Association of State Dam Safety Officials. News Archives. 21 October 2008
  7. Federal Emergency Management Agency. Availability of Dam Insurance, A Report to Congress (1999)
  8. Federal Emergency Management Agency. Federal Guidelines for Dam Safety (2004)
  9. Federal Emergency Management Agency. Draft Report: Dam Safety in the United States, Progress Report on the National Dam Safety Program Fiscal Year 2006 and 2007 (2008)
  10. Federal Emergency Management Agency. Emergency Action Planning for State Regulated High-Hazard Dams; Findings, Recommendations and Strategies (2007)
  11. Federal Emergency Management Agency. Dam Safety and Security in the United States:
  12. A Progress Report on the National Dam Safety Program Fiscal Years 2004 and 2005
  13. Federal Emergency Management Agency. Interagency Committee on Dam Safety Agency Report on the Implementation of the Federal Guidelines for Dam Safety
  14. Federal Emergency Management Agency. The National Dam Safety Program: 25 Years of Excellence (2005)
  15. United States Department of Agriculture, Natural Resources Conservation Service (NRCS) Watershed Rehabilitation Program

Other Resources:

  • National Research Council of the National Academies, Washington, D.C., Assessment of the Bureau of Reclamation’s Security program, (2008)
  • U.S. Army Corps of Engineers. National Inventory of Dams Overview (2007)