ASCE has honored Farshid Vahedifard, Ph.D., P.E., F.ASCE; Firas Jasim; Fred Tracy; Masood Abdollah, S.M.ASCE; Aneseh Alborzi; and Amir AghaKouchak, Ph.D., P.E., M.ASCE, with the 2022 Norman Medal for the paper “Levee Fragility Behavior under Projected Future Flooding in a Warming Climate,” Journal of Geotechnical and Geoenvironmental Engineering, December 2020.
The authors demonstrated effects of changes in future streamflow on the performance of an earthen levee in Sacramento, California, considering multiple modes of failure. The important findings and contributions in the paper are described below:
1. From 1980 to July 2021, inland floods have caused 624 deaths and over $159 billion of CPI adjusted losses in the United States. While several large-scale studies have been conducted for risk and reliability analyses of levees under various loading conditions, there is a clear gap in the state of our knowledge in terms of quantitative and structural-scale assessment of the performance of levees under flooding in a changing climate.
2. This paper presents a multidisciplinary and novel framework that demonstrates how the geotechnical engineering community can closely collaborate with other related disciplines, including climate change scientists, to specifically address the following questions: (a) How does climate change and variability affect recurrence intervals of flooding? and (b) how do climate-adjusted flood patterns affect the short-term and long-term behavior of levees?
3. The authors presented a systematic approach for translating large-scale climate information down to local-scale engineering applications, an aspect that has been indemnified as a critical gap in the state of the art and practice by the 4th National Climate Assessment Model. This framework allows engineers and other stakeholders to perform levee risk analysis while accounting for possible effects of climate change. The authors performed a set of transient coupled finite-element seepage and limit equilibrium slope stability analyses to simulate the levee subjected to extreme streamflow using the historical and future flood levels.
4. The authors showed that future flood events could significantly increase the levee’s probability of failure against individual and combined modes of under seepage, uplift, and slope stability. For all cases, an increase in the flood level of all recurrence intervals significantly impacts the overall stability in the future relative to the past. For the cases examined, the results showed up to a 54 percent reduction in safety factor and an over 100 percent increase in the probability of failure when considering the future versus historical flood scenarios.
5. The approach introduced by the authors can be broadly applied to the nation’s portfolio of levees to quantify the impacts of climate change on the integrity and reliability of levees. Further, the proposed framework can be adopted as a basis for performing risk analysis of other geotechnical structures under changes in climatic extreme events.
The Norman Medal is bestowed upon the author or authors of a paper that is judged worthy of special commendation for its merit as a contribution to engineering science.