In Brief:
The 10 warmest years since record-keeping began 150 years ago were all in the last decade. Warmer air absorbs more moisture, and this moisture is now more and more likely to come down in buckets, increasing the frequency and scale of flood risks to communities.
Climate impacts are making an already-bad situation worse, says Mami Hara, CEO of the nonprofit US Water Alliance. “We were already in a deep hole from underinvestment and systemic inequities of infrastructure investment and services,” Hara says.
Soon enough, the water infrastructure in cities and towns across the U.S. will be regularly pushed to its limits, experts say.
“Virtually all of the infrastructure that we have built was built for a climate that no longer exists,” says Daniel Swain, a University of California, Los Angeles climate scientist who studies relationships between warming and extreme weather. We’re already living in the climate future predicted decades ago, he says, learning that extreme precipitation events are one of its manifestations. Both Hara (who was previously the general manager and CEO of Seattle Public Utilities) and Swain say it’s crucial for local jurisdictions to begin planning for extreme flooding events now.
As a step in this direction, the US Water Alliance brought teams from nine cities together to discuss shared challenges, learn from climate researchers and identify priorities for improving both resilience and equity. Their work was published in a report, Water Rising: Equitable Approaches to Urban Flooding.
The priorities they identified can help communities plan for climate impacts other than flooding, Hara says. But floods are the most common and widespread weather-related disasters. Estimates of their annual cost range from $180 billion to $496 billion a year.
Floods and Public Health
Hampton, Va., was one of the nine cities that participated in the US Water Alliance “boot camp.” It is one of several cities in the state’s Hampton Roads coastal region. Last year the Hampton Roads Sanitation District (HRSD) published the findings of a planning study focused on climate resilience.
John Dano, chief of planning and analysis for HRSD, believes this work could be a model for others scratching their heads about the right way to respond to rising flood risk. “We’re looking at the probability of different storm events that raise water levels to different levels over time, compiling projected damage, and then looking at the payback from different levels of protection,” Dano says.
HRSD examined risks and resources in a regional system that covers 3,000 square miles, serving nearly 2 million people in 20 cities and counties. Floodwater can bring dual risks to this system and the region it serves: sewage overflow, or stormwater inflow that brings operations to a halt.
HRSD operates separately from stormwater management systems in the region, but Dano does have the benefit of economy of scale and the ability to share lessons learned across 150 wastewater facilities. Building system resilience against large-scale events has the added benefit of reducing cumulative damage from smaller ones, he says.
The approach is adaptive, over time and in stages. “We want to have a plan, but we also want to be flexible,” Dano says. “We can’t solve the 70 years in the future problem today, but we can plan for it.”
Moving Target
Flooding caused by heavy rain is increasing more than floods caused by overflowing rivers, according to Swain, the UCLA climate scientist. Thanks to funding from the Bipartisan Infrastructure Law (BIL), the National Oceanic and Atmospheric Administration is beginning a process of updating precipitation estimates to account for climate change, work that will continue until 2027.
This is expected to recalibrate predicted rain depths from “hundred-year” storms (those with a 1 in 100 chance of happening in a year), and how much more frequently today’s “hundred-year” rainfall will burst from the sky. (There’s “strong certainty” that the number of extreme rain events will continue to increase, says Victor Murphy, manager of the climate services program for the National Weather Service).
Past storm patterns are losing predictive value, and these kinds of projections are vital. By the time infrastructure designed today is built, the climate will be even warmer, Swain says. The most extreme events will be more extreme.
Localities must gather and heed this kind of data as they plan for infrastructure improvements, Swain says — and the whole country has to plan for how to fund needed upgrades, according to Hara of the US Water Alliance.
Hara would like to see planning and investment around water become a more regional discussion, in the same way that jurisdictions coordinate on transportation planning. “I’m an advocate for some kind of regional resilience entity that brings together water and climate issues,” she says. California and Maryland are moving in this direction, but it’s not the norm.
The BIL was a monumental step forward, Hara says, but it’s a down payment on the funding that’s needed. The gap between the investments it makes possible and needed infrastructure upgrades is $91 billion annually, a mismatch that the Alliance estimates will continue to grow to $161 annually by 2043 even if funding continued at current BIL levels until then. “We can’t revert back to prior levels of investment,” Hara says. “What we were investing was minimal, not nearly enough to shift the deteriorating state of our country’s water infrastructure.”
