Resilient infrastructure can’t wait

The proper design of stormwater infrastructure, like storm sewers or detention basins, can often be the determining factor standing between extreme rainfall and life-threatening floods. But in most areas across the United States, these systems have not been built to withstand the precipitation depth and intensity projected under climate change.

As a result, communities are increasingly vulnerable to future weather events, facing heightened risks to public health, infrastructure, and economic stability unless climate-resilient planning is prioritized. In a new study published in Environmental Research Letters, researchers recommend four strategies to effectively design and build stormwater infrastructure to prepare for these uncertain future conditions, especially in the absence of such guidance and data from the federal government. 

While we are currently waiting for Atlas 15, that doesn’t mean we have to hold off on designing climate-resilient infrastructure.

David Rounce, Assistant Professor, Department of Civil and Environmental Engineering

The United States National Oceanographic and Atmospheric Administration (NOAA) provides trusted weather information for communities and conducts leading edge research on climate change. In 2004, NOAA established the Atlas 14 information resource to provide communities data on anticipated rainfall estimates, quantifying the amount and probability of rainfall expected during a certain period of time. An update to Atlas 14, known as Atlas 15, was announced in September 2024 and would be the first national precipitation frequency analysis to account for climate change in the U.S. The development of Atlas 15 was briefly paused, but is now reinstated and set for publication in 2026. 

“Every day, communities rely on NOAA information to design infrastructure and keep residents safe. It is imperative that this information accounts for the impacts of climate change,” said Costa Samaras, professor of civil and environmental engineering and director of the Scott Institute for Energy Innovation.

Looking at the mid-Atlantic region – encompassing major cities like Baltimore, Philadelphia, and Washington, DC – researchers applied each of their four strategies and measured effectiveness by calculating a climate-readiness score for the infrastructure in each county to handle future rainfall. 

The first strategy considers designing to the median of current precipitation depth measurements – or, designing for typical rainfall. Despite being a strategy most, if not all, counties in the region currently employ, the study finds that none of the counties are climate-ready under these conditions, leaving them exceedingly vulnerable to future weather events. 

Existing guidance recommends the second strategy, but it is rarely used in practice: designing for the 90th percentile of current precipitation depth, that is, planning for a larger, less frequent storm. Under this approach, 57% of counties would be climate-ready between 2020-2070, but more extreme climate projections between 2050-2100 decrease this amount to only 25%.

The next approach plans for a future where extreme weather is more intense or frequent. Using the median of a larger storm, for example, using a present-day 50-year storm when designing for a future 25-year storm, which refers to a rainfall event that has a 2% chance, instead of a 4% chance of occurring each year, 97% of counties would be climate-ready between 2020-2070, and 50% between 2050-2100.

Finally, the most conservative approach would prepare infrastructure to withstand the worst-case scenario. By designing to the 90th percentile of a larger storm, all counties in the mid-Atlantic region would be protected from increased precipitation projections under climate change from 2020 through 2070. There are, however, disadvantages to over-designing infrastructure including associated costs. Because of this, in practice, decision-makers will rarely design infrastructure for rare events.

“Our findings demonstrate the benefit of an iterative design approach for resilient infrastructure,” said Marissa Webber, lead author of the paper. “Local decision makers must consider the different design strategies, adhere to state and local regulations, and incorporate the priorities of local stakeholders.” 

Webber completed this research as part of her Ph.D. at CMU’s Department of Civil and Environmental Engineering and is now a postdoctoral research associate in the department of Earth Marine and Environmental Sciences at the University of North Carolina at Chapel Hill.

In the interim before the release of Atlas 15, it is important for decision-makers to consider climate change projections when designing all varieties of infrastructure. By prioritizing climate-resilient design, engineers and planners can build systems that adapt to change and continue to protect communities well into the future. 

“While we are currently waiting for Atlas 15, that doesn’t mean we have to hold off on designing climate-resilient infrastructure. We have the data and knowledge to design these systems already,” said David Rounce, assistant professor of civil and environmental engineering. “Here, our goal is to provide straightforward guidance for engineers and planners to ensure the systems we build today will function properly for generations to come.”