Proactively Protecting Communities and Ecosystems from Flooding
Considering the time and planning required to build or update infrastructure, engineers and policymakers could benefit from more efficient ways to prioritize improvements to the countless physical structures that the world relies on for energy, weather protection, transportation, water supply, and more.
Levees—raised embankments that are built parallel to bodies of water to prevent flooding—are in particular need of upgrading. Initially designed to protect agricultural land, these structures protect more than 23 million people, millions of acres of farmland, and trillions of dollars in property in the United States today.
Professor and Louis Berger Chair in Civil and Environmental Engineering Farshid Vahedifard and Ph.D. candidate Mohammed Azhar recently developed an adaptation framework that proposes prioritized upgrades to levees across the United States by assessing their risk under current and future scenarios. Their work, recently published in Water Security, establishes a proactive approach to protecting vulnerable communities and ecosystems from flooding that and supports the co-development of adaptation strategies that minimize this risk over time while balancing technical reliability, economic feasibility, and social equity
Rising to modern-day challenges
“The average age of U.S. levees is 62 years old,” explained Vahedifard. “The performance of these structures can’t keep up with modern-day challenges like precipitation changes, flooding, land subsidence, and soil degradation that can compromise their ability to protect communities, ecosystems, and resources.”
Other infrastructure sectors have developed frameworks to accelerate engineering decision-making and upgrades. For example, projects like Risk Management for Roads in a Changing Climate (RIMAROCC) and Roads for Today, Adapted for Tomorrow (ROADAPT) provide structured approaches to identifying priority road upgrades. Similar frameworks have been developed for drinking water and energy infrastructure.
“We need a similar approach for levee adaptation,” Vahedifard said.
Quantifying the risks and consequences of levee failure
The proposed framework’s goal is to quantify the “risk” of a levee, and how likely it is to fail. For example, two levee-protected areas may face similar flood hazards, but the one protecting a larger and/or more vulnerable population, more critical infrastructure, and greater economic assets would generally face greater risk. With a quantified understanding of levee risk around the country, engineers and other stakeholders can easily identify where to focus efforts and resources to ensure that high-risk levees protecting vulnerable communities are prioritized.
Vahedifard and his collaborators outline five steps for the framework. The first is proposing the “levee risk index.” By assessing levee-protected areas based on factors like climate, hazard exposure, and available resources, this step addresses the difficulties in simultaneously conducting physical, in-depth analyses of the country’s 22,000 miles of levees.
The second step involves stakeholders like watershed managers, levee owners, emergency management agencies, policymakers, and land-use planners validating risk assessments made in step one and ensuring analyses about vulnerability, solutions, budgets, and priorities aren’t made in a vacuum. This step allows engineers to confirm that the levee risk index aligns with what people are actually observing.
To zoom in on high-priority areas, step three involves a more in-depth analysis of levees with the highest risk of failure, using flood models to identify levees that protect large populations or critical infrastructure. Then, structural models help engineers zoom in on these specific levees to get a more precise understanding of how they might fail and the consequences if they do.
Engineers and stakeholders then collaborate to develop potential solutions, from upgrading physical infrastructure to nature-based solutions like wetlands that help absorb water from flooding. The final step establishes continuous monitoring of levee performance to understand and improve the effectiveness of implemented solutions.
A proactive approach to levee upgrades
“What began as a research effort has gradually evolved into a broader vision for risk-informed, resilient, and equitable infrastructure, and even inspired the development of a new graduate course at Tufts, CEE 183: Resilient and Equitable Infrastructure,” said Vahedifard.
Although this framework is designed for levees, the concept can be applied to upgrading other critical infrastructure systems, serving as an example of how to take a proactive approach to developing collaborative, holistic, and just engineering solutions.
As modern-day infrastructure upgrades are often reactive, this framework allows engineers and stakeholders to take a proactive approach to levee adaptation that can help identify the country’s most vulnerable levees and prevent the social, economic, and environmental degradation that often comes with their collapse.