On This Page
Issues and Challenges
- Dams in the U.S.
- The Increasing Hazard: Summary of US Dam Data
- The Owners’ Responsibility
- Lack of Adequate Oversight: Summary of Current Regulatory Programs in the US
- Risk of Failure: Failures and Incident Stats
- The Need for Rehabilitation and Financing for These Upgrades
- Emergency Preparedness
- Outdated or Generalized Precipitation Data
- Lack of Transparency and Communication with the Public
A Call to Action. What Can We Do to Improve Dam Safety?
- ASDSO
- States and Federal Governments
- The National Dam Safety Program
- The U.S. Congress
- Dam Owners
- Emergency and Floodplain Managers
- Citizens
Issues and Challenges
Dams are a critical part of the nation’s infrastructure—equal in importance to bridges, roads, airports, and other major elements of the infrastructure. Dams provide a life-sustaining resource to people in all regions of the United States. They can serve several functions at once, including water supply for domestic, agricultural, industrial, and community use; flood control; recreation; and clean, renewable energy through hydropower. Yet thousands of US dams have the potential to fail with tragic consequences. Our nation’s dams are aging and deteriorating while downstream populations are increasing. This situation demands greater attention to and investment in measures that reduce risks to public safety and economic assets.
Dams in the U.S.
Throughout the history of the humankind, people have built dams to maximize use of this vital resource. Dams were built to
provide a life-sustaining resource to people in all regions of the United States. The 20th Century saw the most prolific building of dams in the U.S. With that came dam failure. Early in that century, as many dams failed due to lack of proper engineering and maintenance, it was recognized that some form of regulation was needed. One of the earliest state programs was enacted in California in the 1920s. Federal agencies, such as the USDA, Soil Conservation Service, the US Army Corps of Engineers and the Department of Interior, Bureau of Reclamation built many dams during the early part of the twentieth century and established construction and safety standards during this time. Slowly, other states began regulatory programs. But it was not until the string of significant dam failures in the 1970s that awareness was raised to a new level among the states and the federal government.
The Increasing Hazard: Summary of US Dam Data
Dams are innately hazardous structures. Failure or mis-operation can result in the release of the reservoir contents - this includes water, mine wastes, or agricultural refuse - causing negative impacts upstream or downstream or at locations remote from the dam. Negative impacts of primary concern are the loss of human life, economic loss including property damage, lifeline disruption and environmental damage.
Some dams are considered to have a greater hazard potential than others. As of 2021, there are approximately 16,500 high-hazard potential dams in the United States. "High-hazard potential" is a term used by a majority of state dam safety programs and federal agencies as part of a three-pronged classification system used to determine how hazardous a dam's failure might be to the downstream area.
While the definition varies from place to place, it generally means if failure of a high-hazard dam occurs, there probably will be loss of life. It must be emphasized that this determination does not mean that these dams are in need of repair - these dams could be in excellent condition or they could be in poor condition. High hazard just reflects the dam's potential for doing damage downstream should it ever fail.
High-hazard potential dams exist in every state and affect the lives of thousands downstream. The current issue and debate is over the increasing number of these high-hazard structures - not because more high-hazard dams are being built, but that more development is occurring downstream. Dam safety regulators generally have no control over local zoning issues or developers' property rights, and so this issue continues to worry regulators as the "hazard creep" trend persists.
The Owners’ Responsibility
Dams are owned and operated by many different types of owners. Sometimes they only serve the interest of the owner—for instance in the case of a neighborhood association that wants its 
homes built around a lake—and sometimes they serve the interest of communities—for instance in the case of a water supply utility.
Private ownership makes dams a unique part of the national infrastructure. While most infrastructure facilities (roads, bridges, sewer systems, etc.) are owned by public entities, the majority of dams in the United States are privately owned.
A dam owner is solely responsible for the safety and liability of the dam and for financing its upkeep, upgrade, and repair.
Lack of Adequate Oversight: Summary of Current Regulatory Programs in the United States
It is important that there is regulatory oversight to reduce the risk of dam failure or incidents. The safety of the majority of dams in the U.S. is regulated – by state agencies or federal agencies or by self-governance as with many federally owned dams such as the Army Corps of Engineers or the US Bureau of Reclamation.
State dam safety programs have primary regulatory responsibility for almost 75% of the nation’s dams. State dam safety programs oversee classification, permitting, and inspection of dams, provide enforcement, oversee remediation of deficient dams, and work with local officials and dam owners on emergency preparedness.
Although most states have legislative authority to carry out a comprehensive dam safety program, many are lacking in specific areas. Some states are unable, by specific language in their law, to
regulate certain types of dams, allowing these structures to fall between the regulatory cracks. Other states have limited ability to enforce the law. In some states, officials have no recourse if dam owners do not carry out safety repairs ordered by the state.
Many states are simply under-resourced for carrying out the letter of the law. In FY 2021, state budgets for dam safety ranged from $0 (Alabama) to $20 million (California). But the average annual state dam safety budget is about $1.26 million. The average number of regulated dams per state is about 1700. The average number of dam inspectors per state is about nine. This means that each dam inspector is responsible for overseeing the safety of about 190 existing dams, plus the additional responsibilities of overseeing new construction.
Bottom line, many state programs lack adequate budgets, staff and authority to carry out these duties and to ensure public safety. Although things have improved in the last 20 years, there is an ongoing, serious need in almost every state to pump additional state resources into these programs.
Risk of Failure: Failures and Incident Stats
Dam failures not only risk public safety, they also can cost our economy millions of dollars in damages. Failure is not just limited to damage to the dam itself. It can result in the impairment of many other infrastructure systems, such as roads, bridges, and water systems. When a dam fails, resources must be devoted to the prevention and treatment of public health risks as well as the resulting structural consequences.
Hundreds of dam failures have occurred throughout U.S. history. These failures have caused immense property and environmental damages and have taken thousands of lives. As the nation’s dams age and population increases, the potential for deadly dam failures grows.
Although the majority of dams in the U.S. have responsible owners and are properly maintained, many dams still fail every year. From January 2010 to April 2020, states have reported 270 dam failures and 581 'incidents' - episodes where dams could have failed without intervention or if circumstances had not abated. Dam and downstream repair costs resulting from failures in 23 states reporting in one recent year totaled $54.3 million.
Historically, dams that failed had some deficiency, which caused the failure. Currently, the number of deficient high-hazard potential dams is more than 2,330. There are deficient dams in almost every state. The risk of failure only increases as dams across the nation age. Currently, the average age of dams in the United States is 61 years. By 2025, 73% of dams in the National Inventory of Dams with a completed date listed will be over 50 years old. Without the needed upgrades and rehabilitation, these dams cannot be expected to withstand current flood and earthquake predictions.
The Need for Rehabilitation and Financing for These Upgrades
Lack of funding for dam upgrades is a serious national problem, especially within the private sector. Operation, maintenance, and rehabilitation of dams can range in cost from the low thousands to millions, and responsibility for these expenses lies with owners, many of whom cannot afford these costs. Although some states offer loan programs, for the most part funding assistance through either government or private sources is minimal at best.
Dams must be maintained to keep them safe. Occasional upgrade or rehabilitation is necessary due to deterioration, changing technical standards, improved techniques, better understanding of the area's precipitation conditions, and changes in downstream populations or land use. When a dam's hazard classification is changed to reflect an increased hazard potential, the dam may need to be upgraded to meet an increased need for safety. The age of a dam is not necessarily a direct indicator of its condition. Age is indirectly an indicator in that old dams were not built to the standards of today. Some older dams are considered in poor condition for this reason alone, while others may have been inadequately maintained as well.
In 2021, the American Society of Civil Engineers updated its Infrastructure Report Card. In this report, dams were given a 'D.’ This is mostly due to the number of deficient high-hazard dams and the lack of funding the sector currently receives. The full report is available here.
Thousands of dams remain in need of rehabilitation to meet current design and safety standards. These structures are not only aging but are subject to stricter criteria because of increased downstream development and advancing scientific knowledge predicting flooding, earthquakes, and dam failures. The average age of our nation’s dams is 61 years. By 2025, seven out of 10 dams in the United States will be over 50 years old. Fifty years ago, dams were built with the best engineering and construction standards of the time. However, as the scientific and engineering data have improved, many dams are not expected to safely withstand current predictions regarding extreme storms, large floods and earthquakes. In addition, many of these dams were initially constructed using less-stringent design criteria for low-hazard potential dams due to the lack of development downstream.
In a 2023 report, ASDSO estimated that the total cost to rehabilitate the nation’s non-federal dams is $157.5 billion. The cost to rehabilitate just the most critical dams was estimated at $34.1 billion, a cost that continues to rise as maintenance, repair, and rehabilitation are delayed. Many dam owners, especially private dam owners, find it difficult to finance rehabilitation projects.
Read ASDSO's Cost of Rehabilitating Dams in the U.S.
Emergency Preparedness
Emergency planning and preparedness procedures must be in place in the event of an incident or failure. Until the last 10 plus years, a large percentage of dams in the U.S. did not have Emergency Action Plans or exercising procedures in place. Emergency Action Plans (EAPs) play a big role in keeping people and property safe in the event of a dam breach or failure. Several states are making notable progress on increasing the percentage of dams with EAPs.
Emergency preparedness is improving, with the percentage of state-regulated high-hazard potential dams with an Emergency Action Plan (EAP) increasing. The goal is for all high-hazard potential dams to have an EAP so that dam owners and local authorities are prepared for a sudden dam failure and the ensuing downstream consequences.
Outdated or Generalized Precipitation Data
National extreme rainfall (Probable Maximum Precipitation [PMP]) standards have long been used for regulation and design of high-hazard potential infrastructure including dams and nuclear power facilities. Those standards are used to bring consistency between Federal Agencies, State Agencies, and the private sector professional design community. Federal leadership is again needed to update these standards.
The US National Oceanic and Atmospheric Administration (NOAA), National Weather Service (NWS) first developed methodologies for estimating probable maximum precipitation (PMP) in the 1940s and, using historic data available at that time, applied them across the US through hydro and hydrometeorological studies and reports between 1961 and 1999. State dam safety programs have developed statutes, rules and guidance documents for design of safe facilities that are typically based on these federally sanctioned NWS studies.
Decades of storm event data (the basis for calculating the standards) have been recorded since the existing standards were published. These reports, however, have never been officially updated to include new methods, technologies, or decades of more recent storm data libraries.
These outdated reports continue to be used by many. Some state dam safety programs have changed their statutes to allow use of available new methodologies provided by entities outside the federal government and others find it too difficult to attempt. Inconsistencies between minimum design criteria of adjacent states and between federal and state design / performance expectations within states are increasing.
It has recently been reported that there are nearly 1700 high-hazard potential dams currently in need of repair across the country. It is reasonable to assume a percentage of those dams need spillway system improvements. Consistent and standardized modern methodologies for repair of spillways at high-hazard potential dams rated unsatisfactory are needed in order to ensure the highest level of public safety.
Lack of Transparency and Communication with the Public
Intersecting almost all the issues above is the issue of public education about dams. The ordinary citizen is unaware that the beautiful lakes on which they boat, ski, or fish are only there because of manmade dams. Developers build in dam-break flood inundation areas knowing nothing about the potential devastation an upstream dam could cause should it ever fail. In fact, some developers and zoning officials are completely unaware of dams within their community. Even if citizens understand and are aware of dams, they still can be overly confident in the infallibility of these manmade structures. Living in dam-break flood-prone areas is a risk.
Many dam owners do not realize their responsibility and liability toward the downstream public and environment. Adequate understanding of proper dam maintenance and upgrade techniques is a typical problem among many owners across the United States.
Some groups put forth the message that dams are bad for the environment and advocate their removal. This may mislead the public into thinking that taking care of our dams is a worthless cause. In some cases, dam removal is the best solution, but in all instances the consequences should be considered before coming to this decision.
A Call to Action: What Can We Do To Improve Dam Safety?
ASDSO Shall:
✓ Support the improvement of state dam safety programs.
✓ Increase collaboration.
✓ Advance and expand the technical expertise of dam and levee safety practitioners through training and education programs.
✓ Reduce the potential for dam failure by promoting innovative approaches to fund dam rehabilitation.
✓ Reduce the consequences of dam failure by increasing public awareness, planning and preparedness.
✓ Advocate for laws, policies and government programs that serve to improve the safety of dams and reduce the risk to the public.
✓ Support and strengthen a coordinated effort to improve the safety of levees.
Read ASDSO's Strategic Plan 2022-2027
States and Federal Governments Should:
✓ Maintain and Constantly Review and Improve Dam Safety Regulatory Laws, Policies and Programs. (Learn and Adapt).
✓ Provide sufficient resources, staffing and regulatory authorities to State and Federal dam safety programs.
✓ Ensure that adequate data on dams is available to policymakers to facilitate decision-making on funding, and to the general public to promote public awareness.
✓ Ensure that Federal agencies that own, operate, or regulate dams should meet the standards of Federal Guidelines for Dam Safety.
✓ Ensure that State agencies who regulate dams work toward meeting nationally accepted guidance detailed in the Model State Dam Safety Program Guidelines.
✓ Educate dam owners and encourage owners to use experienced professional engineers.
✓ Implement innovative grant or loan programs to shore up deficient dams, similar to the Superfund Program administered by the EPA.
✓ Effectively implement existing federal grant and loan programs including:
- the High-Hazard Potential Dam Rehabilitation Program, a national grant program administered by the FEMA National Dam Safety Program
- the Water Infrastructure Financing Program (CWIFP), a national program administered by the US Army Corps of Engineers to provide low-interest loans to dam owners for rehabilitation funding gaps
- the Small Watershed Dam Rehabilitation Program, administered by the Natural Resources Conservation Service, to provide grants for rehab of dams owned by watershed districts throughout the US
✓ Create State-administered low interest loan and grant programs for dam rehabilitation or fully fund the ones that States have on the books.
✓ Improve Downstream Hazard Classification (DHC) practices to ensure the safety of people downstream.
✓ Work with dam owners to develop emergency action plans for every high-hazard potential dam. Use a nationally accepted model/guide. Integrate exercising into the planning process.
✓ Encourage improved land use planning at the local level so that communication about how dams affect local areas is more accurately known and considered in future planning.
✓ Implement better public education about high-hazard potential dams, specifically ensuring the public has a better understanding of the dam condition rating system.
✓ Update hydrometeorological models and tools to account for what is known about climate change and current data.
✓ Work toward better communications to reduce the consequences from failure. Share inundation maps and emergency response plans for high hazard potential and significant hazard potential dams.
✓ Encourage better coordination between regulatory agencies (federal and state) regarding regulatory communication.
The National Dam Safety Program Should:
✓ Facilitate and support the strengthening of State dam safety programs.
✓ Increase and improve training programs for dam safety engineers (including regulators, engineering consultants, owners with operators). Use one nationally accepted Dam Engineering and Risk Management Program of Study.
✓ Maintain nationally accepted guidelines on dam safety program management, dam engineering and dam risk management technical topics. These national guidelines should be maintained and routinely updated by the FEMA, National Dam Safety Program.
✓ Effectively implement the National High-Hazard Potential Dam Rehabilitation Program to cost-share safety upgrades to non-federal, high-hazard potential dams across all States.
✓ Implement a national public awareness campaign to educate individuals on the location and condition of dams in their area and become more “dam aware.”
✓ Establish a national investigation program, which would be activated after dam failures or incidents, to provide important lessons to be learned from those failures.
✓ Promote a coordinated strategy within the dam safety community to study, archive and disseminate lessons to be learned from failures and incidents.
✓ Encourage better coordination between regulatory agencies (federal and state).
The U.S. Congress Should:
✓ Support and fully fund FEMA's National Dam Safety Program and CISA's Dams Sector Specific Agency to increase national coordination and support for dam safety and security.
✓ Support and provide increased appropriations for all federal dam rehabilitation loan and grant programs.
✓ Review the implementation of the High-Hazard Potential Dam Rehabilitation Program, administered by FEMA, to assure that common sense, equitable and effective strategies are being used by FEMA to carry out the program.
✓ Provide appropriations to support implementation of the US Army Corps of Engineers’ Water Infrastructure Financing Program, which provides low-interest loans for dam rehabilitation.
✓ Provide adequate resources to all Federal agencies that own, regulate or provide technical or research support for dams.
Dam Owners Should:
✓ Maintain and operate dams to assure that the they do not fail. Work with state local officials to mitigate the consequences of failures and incidents.
✓ Inform local officials of risks associated with dams.
✓ Develop emergency action plans (EAP) for every high-hazard potential dam. Use a nationally accepted model/guide. Integrate exercising into the planning process.
✓ Have a dam failure inundation map created as part of the EAP development process. Share plans and maps with local planners and first responders.
✓ Work with the state or federal regulator to comply with safety standards.
✓ Hire experienced professional engineers to oversee dam safety engineering issues.
✓ Attend educational programs when offered by organizations and agencies.
Emergency and Floodplain Managers Should:
✓ Open lines of communication with State and Federal dam safety agencies to improve planning and preparedness for dam failures or incidents.
✓ Participate in educational programs to become more aware of dams and how they intersect with emergency and floodplain management.
✓ Encourage improved land use planning at the local level so that communication about how dams affect local areas is more accurately known and considered in future planning.
Citizens Should:
✓ Be aware of their surroundings, risks they may face, and steps they can take now to protect themselves and their families from floods should a dam fail or release flood waters.
✓ Have a plan in place if an evacuation becomes necessary. Listen to first responders and emergency managers and follow directions given in the event of a dam incident or failure.
