Heavy rains, made more frequent and severe by climate change, lead to floods.
Floods can cause dams to overflow, either over or around them, which poses a serious risk. These conditions can result in erosion, leading to dam breach or failure and sudden and uncontrolled bursts of water.
Dam failure can result from the combined effect of extreme natural events, such as storms and floods, and an aging, poorly maintained dam.
Today’s dams average between 50 and 100 years old, and many still operate past their lifespan. The frequency and intensity of extreme events mean that these dams may need to be adapted to deal with the pressures of climate change (Barroud, 2023).
34% of dam failures result from overtopping. The consequences of damages depend on the dam’s proximity to development. The damage could be massive if dams are located near homes, businesses, and critical infrastructure.
A 2024 report by the United Nations University (UNU)’s Canadian-based Institute for Water, Environment and Health, “Ageing water infrastructure: An emerging global risk,” offers an overview of dam aging, examining key trends in many countries worldwide and their primary functions, such as water supply, irrigation, flood control, hydropower, and recreation.
The report shows that tens of thousands of existing large dams have reached or exceeded the “alert” age threshold of 50 years. Many others are nearing 100 years, highlighting the rising risks associated with aging dams, such as rising maintenance costs, reduced functionality due to sediment build-up, and the benefits of restoring or redesigning natural environments.
The report also includes case studies of the aging or decommissioning of dams from countries like the United States, Canada, Japan, France, India, Zambia, and Zimbabwe.
According to the International Commission on Large Dams (ICOLD), there are over 58,700 large dams. Large dams are defined as having a height of 15 meters or more from the lower foundation to the crest or dams that impound more than 3 million cubic meters. North America and Asia hold 16,000 large dams between 50 and 100 years old and 2,300 large dams over 100 years old.
According to the American Society of Civil Engineers (ASCE) 2017 report, the average age of all 90,580 dams (of all sizes) in the USA is 56 years. Over 85% of these dams will reach their end-of-life expectancy in 2020, and 70% will be over 50 years old by 2030.
Overall, the ASCE graded the US dams “D” and estimates that more than 2,300 have high-hazard potential. If they fail, they could cause loss of life or severe property damage due to the proximity of development around them.
The Conversation article notes that decommissioning or replacing dams can be complex and costly, with cascading effects on the surrounding community and other infrastructure.
Regular maintenance and upgrades are the most cost-effective way to strengthen aging dams and make them resilient to natural hazards. However, dams can be partially breached or removed to restore the river’s natural flow when they cease serving their purpose.
The rehabilitation cost of all non-federal dams in the US would be around US$ 157.7 billion.
Climate change is making extreme events more severe and frequent. For instance, in 2015, a 1-in-1000-year rainfall event in South Carolina breached 47 dams.
The changing climate calls for upgrading existing dams based on a design considering future climate projections. Older dams were built under a past climate and not the one unfolding today and in the future, making them vulnerable to climate change. The situation calls on authorities to take proactive steps, such as regular and better maintenance of aging dams, upgrading to build resilience when necessary, and developing emergency action plans.
Watch this video from Practical Engineering showing the near-failure of California’s Oroville Dam in February 2017. This caused the evacuation of nearly 200,000 residents living downstream.
Factors contributing to the near breach of the dam included design and construction flaws and lapses in regular inspections.
A key message from this post and the video is not to neglect dams in infrastructure management planning.
Sources:
Baroud, H. (2023, July 14). Climate change is increasing stress on thousands of aging dams across the US. The Conversation. Retrieved from https://theconversation.com/climate-change-is-increasing-stress-on-thousands-of-aging-dams-across-the-us-209568
Perera, D., Smakhtin, V., Williams, S., North, T., & Curry, R.A. (2021 January). Ageing Water Storage Infrastructure: An Emerging Global Risk 11. United Nations University. Retrieved from https://www.researchgate.net/publication/348754254_Ageing_Water_Storage_Infrastructure_An_Emerging_Global_Risk_11
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