The following post is a review of the new report “Modernizing Probable Maximum Precipitation Estimation” published by The National Academies Press.
For over 75 years, engineers in the U.S. designed high-hazard structures, such as dams and nuclear power plants, to endure floods resulting from the infrequent but possible precipitation events known as Probable Maximum Precipitation (PMP). The failure of any of the more than 16,000 high-hazard dams and 50 nuclear power plants in the country can lead to significant loss of life, immense economic costs, and extensive environmental harm — particularly under the stresses induced by climate change.
To date, PMP estimates provided essential guidance for the design of critical infrastructure. However, deficiencies in scientific underpinnings and advances in storm understanding, observation, and modeling necessitate significant revisions to the PMP definition and its estimation methods. The potential risks of not addressing these deficiencies can be catastrophic, underscoring the urgency and importance of this issue.
A recent report from the National Academies advocates for a redefined PMP and presents a new methodology for its application in the design, operation, and regulation of essential infrastructure. This updated definition focuses on precipitation depths with an ‘extremely low exceedance probability’ instead of presuming a bounded rainfall limit. It considers specific climate periods to allow PMP estimates to adapt to climate changes. Immediate improvements to PMP include better data collection, model-based storm reconstructions, and a more robust scientific foundation for PMP methodologies.
Over the long term, kilometer-scale climate models capable of resolving PMP storms will be used for model-based PMP estimation, providing more precise PMP-magnitude precipitation data. A Model Evaluation Project will validate the scientific basis for model-based PMP estimation and determine the appropriate timing for transitioning to this approach. Progress in scientific research and modeling will play a crucial role in addressing the societal challenges posed by extreme storm and precipitation changes in our warming climate, which are essential for ensuring public safety and infrastructure resilience.
Contributor(s): National Academies of Sciences, Engineering, and Medicine; Division on Earth and Life Studies; Board on Atmospheric Sciences and Climate; Water Science and Technology Board; Committee on Modernizing Probable Maximum Precipitation Estimation
(Source: National Academies of Sciences, Engineering, and Medicine. 2024. Modernizing Probable Maximum Precipitation Estimation. Washington, DC: The National Academies Press. https://doi.org/10.17226/27460.)
© 2024 National Academy of Sciences. All rights reserved.
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