A century of dam safety: Five key insights
Expert(s) |
Antonio Moreno Rodenas
Dams are essential for flood protection, water resources management, energy, and food security. However, their failure can lead to devastating consequences, as recent disasters have demonstrated. A new study, published in Nature Water by researchers from Deltares, IHE Delft, and Imperial College London, presents a detailed global analysis of dam failure probability from 1900 until present. This work unveils key factors behind the evolution of large dams’ failures and offers insights into future trends.
Dam safety as a discipline emerged in the 20th century, integrating expertise from hydraulic, geotechnical and mechanical engineering, alongside statistical analysis. Driven by lessons from past failures, this approach has shaped modern dam design, construction, and risk management practices.
This research has applied for the first time a formal statistical survival modelling approach to the modern dam failure records, allowing the incorporation of new aspects of dam safety. This explicitly considers aspects like climatic regions, the dam owner’s resources, age, and changes in construction efforts and trends. By reanalysing and updating the historical records from the International Commission on Large Dams on dam failures, this research provides a structured evaluation of dam failure probabilities at global scale.
Five new insights
The researchers identified five new insights with regards to long-term safety trends and the factors shaping contemporary dam safety. These insights are:
1. Sustained safety improvements over the 20th century
The probability of a large-dam failure has decreased consistently, with failure rates dropping by an average of 30% per decade since the early 1900s up to the end of the century. Dams built on a given epoch retain to a good extent the safety of those times, which might be linked to construction methods and design techniques of the time. Countries that experienced major dam failures have effectively “learnt” from those catastrophic experiences.
2. Early failures remain a critical factor
This old-known vulnerability remains, at least for embankment dams. Dams are more likely to fail during the first five years after construction than during the following 45-55 years. This study further highlights the temporal evolution of this early failure effect, which has strongly reduced, particularly for concrete dams.
3. No significant evidence of aging-related failures
While concerns about aging infrastructure are often raised, this research did not find a substantial increase in dam failures due to aging. Data shows that dams built at the beginning of the 20th century exhibit a clearly higher probability of failure, possibly linked to inherent outdated designs and construction practices, but this probability does not yet seem to accelerate over time.
4. A concerning reversal: rising failure rate of newly built dams
Since the 2000s, failure rates for newly built dams have increased for the first time in a century, reverting advances of the previous decades. This trend is linked to latest dam construction in low-income countries, especially where catastrophes have not been experienced before in the recent past.
5. Highest failure rate today linked to tropical zones and flooding
Highest failure rates of dams are currently observed in monsoon-tropical regions, especially in regions with lower purchasing power. While traditionally, structural, mechanical, and geotechnical failures have been relatively common, new failure statistics are increasingly dominated by flooding context. This research cannot attribute the recent surge in dam failure rates to climate change, but raises the need to conduct local specialised studies.
What makes a dam more prone to failure?
Dam safety is a complex matter, which requires very detailed knowledge on each structure’s state, design and local characteristics. However, this analysis formally retrieves insights using data available for a very large number of dams. This type of analysis cannot pinpoint the real state of an individual dam, but can be very useful to prioritise attention on critical structures based on their characteristics.
Using a classification technique, this study identifies common characteristics of high-risk dams, which majorly comprehend dams built in the beginning of the 20th century or newly built (<10 years) embankment dams in low-GDP countries.
Looking at the future
This analysis identified that the current average failure probability remains well below the strictest accepted failure probability of 1 in 10,000 annually, with 85% of dams being at least twice as safe. However, with a global portfolio of 62,000 large dams in 2024, failures are inevitable. This research estimates 23 failures of large dams between 2023 and 2035. Yet these projections do not account for the construction of new dams, the consequences of climate change, or human conflicts, which could influence failure rates and lead to higher numbers.
Identifying inherent risks—through a combination of failure probability assessment and impact evaluation on downstream populations and infrastructure—is essential for guiding risk-informed decision-making. A proactive approach that integrates monitoring, maintenance, and policy interventions will be crucial to ensuring that dam safety keeps pace with changing environmental and socio-economic conditions.
Our future predictions align with 120 years of observed trends, yet it remains key to monitor evolving risk factors.
Antonio Moreno-Rodenas (Lead author and hydraulic engineer at Deltares)
Dam safety expert at Deltares and lead author, Antonio Moreno-Rodenas, emphasises the study’s significance: "Dam safety is a complex issue that depends on detailed knowledge of each structure’s condition, design, and operational environment. Our future predictions align with 120 years of observed trends, yet it remains key to monitor evolving risk factors—such as deglaciating basins, increasing extreme events, and geopolitical conflicts. Ensuring we accurately quantify these risks is crucial to supporting effective policies for dam safety."
Flood-resilient communities
The research team is now expanding their work to improve the understanding of risks and benefits around dams. Daniel Valero (Imperial College) highlights that “keeping reservoirs safe is critical to meet water, food and energy challenges that many countries are already intensely experiencing”.
The collaboration between Imperial College London and Deltares also works towards accelerating current dam safety profiling, through the use of artificial-intelligence and remote sensing to map infrastructure, and the rapid evaluation of vulnerability and population at risk. These efforts aim toward enhancing dam safety and ensuring flood-resilient communities worldwide.
