From the rise of artificial intelligence for flood detection to the rise of strategic beaver deployment, from reimagined golf courses in Houston to living shorelines along the Florida coast, and from centralizing green infrastructure guidance to expanding the Saffir-Simpson scale, 2024 has been a banner year for the stormwater sector.

With 2025 just around the corner, take a fresh look at Stormwater Report’s five most popular articles from this year.

#1: EPA Clean Watersheds Needs Survey Delivers Sticker Shock

In a sobering report delivered to U.S. Congress on May 13, U.S. Environmental Protection Agency (EPA) researchers estimated that the combined wastewater and stormwater sectors require approximately USD $630 billion in new federal funding during the next 20 years to address existing and anticipated water quality problems.

The most recent Clean Watershed Needs Survey (CWNS), administered by the U.S. Environmental Protection Agency (EPA), estimates that the U.S. wastewater and stormwater sectors will require more than USD $630 billion over the next 20 years to meet the goals of the Clean Water Act. Although this is the 17th CWNS produced by EPA, it is the first since 2012 and the first ever to include data from all 58 U.S. states and territories. Image courtesy of EPA

This figure resulted from EPA’s first Clean Watersheds Needs Survey (CWNS) administered since 2012, which polled more than 17,500 publicly owned wastewater and stormwater management providers nationwide about their financial needs. Compared to the previous CWNS installment, stated needs among stormwater managers saw the most significant increase of any segment polled — approximately USD $115.3 billion, a 385% increase over 2012 estimates.

Drilling down further, needs associated with designing, deploying, and maintaining green infrastructure represented the fastest-growing expenses among U.S. stormwater managers. Green infrastructure-related expenses increased from 15% to 43% of the stormwater sector’s total stated needs since the 2012 CWNS. The survey also found stormwater needs to be highly concentrated by region. Only three U.S. states — Virginia, California, and Florida — together reported roughly half of the country’s stormwater funding gaps.

Read “EPA: Achieving Clean Water Act Goals Requires $630 Billion+ Over Next 20 Years” for more details on this year’s CWNS results and what they mean for federal stormwater funding.

#2: New FEMA Policy Rewrites Floodplain Rules

Certain critical infrastructure projects are facing more stringent regulatory requirements in light of the new Federal Flood Risk Management Standard (FFRMS) policy, implemented by the U.S. Federal Emergency Management Agency (FEMA) on September 9.

U.S. Federal Emergency Management Agency (FEMA) will use this flowchart to determine whether a given site constitutes a regulatory floodplain, representing the first step of FEMA’s 8-Step Decision Making Process by which they decide whether the agency’s new Federal Flood Risk Management Standard rules apply to a potential project. Image courtesy of FEMA

The FFRMS, which applies to federally funded development projects, climate adaptation measures, and substantial repairs to critical structures, expands the criteria for what qualifies as a regulatory floodplain. Previously, any critical infrastructure project located in an area that met conventional definitions for a “500-year floodplain” was subject to more stringent design standards to ensure resilience against major flood events. In place of this one-size-fits-all measure, the FFRMS incorporates the latest projections of potential flood extent and elevation for a given project area to determine whether that project should conform to the heightened design standards. FEMA also announced that the federal government would cover up to 75% of the costs associated with FFRMS compliance.

The FFRMS elicited strong reactions from the stormwater management community. Professionals lauded the inclusion of climate projections into floodplain determinations, but expressed concerns about the increasing complexity of design and siting for critical infrastructure that could expand project timelines — particularly for small communities with fewer financial and technical resources. They also voiced doubts about FEMA’s bandwidth to implement the new policy in an equitable manner.

Read “Stormwater Professionals React to New FEMA Floodplain Standards” for insights on the FFRMS and its ramifications for critical infrastructure.

#3: Solving a Stormwater Management Mystery in Philadelphia

In May, the Pennsylvania Department of Transportation (PDOT) announced results from a 4-year investigation into the health of the city’s roadside bioretention basins, conducted alongside researchers from Temple University (Philadelphia) and Villanova (Pennsylvania) University. Their conclusions have the potential to improve the design of these critical green infrastructure elements in similar settings worldwide.

The Pennsylvania Department of Transportation commissioned a research team, including Josh Caplan (right), Associate Professor of Horticulture at Temple University (Philadelphia), to investigate why plants were dying in Philadelphia’s bioretention basins. Image courtesy of Joseph V. Labolito/Temple University

It is normal for vegetation-based infrastructure in climates with cold winters to enter dormancy and turn from green to brown for part of each year. In Philadelphia, however, PDOT noticed that roadside bioretention basins citywide remained brown even during peak-bloom season — severely undermining the basins’ treatment functions. A thorough investigation pinpointed excessive roadway-deicing salt as the culprit, accumulating to a point where some basins had the same salinity as ocean water even despite effective drainage.

Findings from this study informed a new paradigm for how PDOT selects suitable plants for roadside bioretention basins. Regarding salt tolerance as a spectrum more than a binary trait, they identified a list of 13 native plant species of suitable size for bioretention basins able to better withstand the impacts of road salt, such as seaside goldenrod, common rush, and feather reed grass.

Read “Researchers Determine Mystery Cause Behind Brown Bioretention Basins” to follow the investigation from start to finish.

#4: Tiny Forests Reach the Big Apple

New York City plunged deeper into the green infrastructure pool this year, unveiling a USD $6 billion plan to flood-proof the city’s transit system and installing an unprecedented 11 km (7 mi) of porous pavement along Brooklyn roadways, among other large-scale efforts. However, one New York City-based project caught the eyes of Stormwater Report readers more than any other: the city’s first pocket forest planted on Manhattan’s Roosevelt Island.

Hundreds of volunteers gathered to plant the 1,500 trees and shrubs included in New York City’s first “pocket forest.” The planting event also featured speakers, dancers, and musical performances. Image courtesy of Dino Kuznik/SUGi

In April, a coalition of nature-minded nonprofits planted the seeds of the Manhattan Healing Forest, a series of 1,500 trees planted within an ultra-compact 372-m2 (4,000-ft2) space. This pocket forest is emblematic of a new type of green infrastructure gaining worldwide prominence, pioneered by Japanese botanist Akira Miyawaki. It involves planting dense, multi-layered forests consisting of many different tree species, with plantings as close together as three to four saplings per square meter arranged in a randomized pattern.

Pocket forests grow up to ten times faster than monoculture forests while providing outsized ecological benefits for the footprints they occupy. These benefits include, for example, enhanced carbon capture, pollution filtration, resistance against flooding, reduced urban heat-island effects, and protection against storm surge.

Read “First-of-Its-Kind ‘Pocket Forest’ Planted in New York City” to get a glimpse of this emerging approach to nature-based stormwater management in dense, urban areas.

#5: Montreal Sponge Parks Balance Resilience and Recreation

On the opposite end of the size spectrum from pocket forests, in Montreal, municipal stormwater professionals are embracing a maximalist approach to green infrastructure with an ongoing sponge park campaign. The city is midway through an initiative to construct more than 30 sponge parks — large, public amenities designed around green infrastructure at the foundational level — by the end of 2025. City crews broke ground on the campaign’s largest planned sponge park in May.

The City of Montreal is constructing its largest-ever “sponge park” — a green infrastructure-focused public space meant to maximize stormwater infiltration — as part of a long-term campaign to mitigate combined sewer overflows and improve the city’s flood resilience. The park, located in the Verdun neighborhood, is one of more than 30 such parks under construction by the end of 2025. Image courtesy of City of Montreal

Montreal’s largest sponge park, located in the riverside Verdun neighborhood, spans 4,300-m2 (152,000-ft2) with a total stormwater retention capacity of approximately 1,067,000 L (282,000 gal). It transforms an empty lawn located on land adjacent to Montreal’s Atwater drinking water treatment facility — a low-lying area straddling two of Verdun’s busiest avenues that experiences chronic flooding during even modest storms.

The project, with a cost just below CAD $2.5 million, features numerous strategically placed amenities that strike a balance between sound stormwater management and recreation for the surrounding community. For example, the design calls for a new dog park and bike path as well as a network of carefully designed ditches and vegetated pits. Drinking fountains around the property discharge undrunk water into the ditches rather than back into the municipal water supply to help moisten the soil and preserve infiltration capabilities.

Read “Montreal Breaks Ground on City’s Largest-Ever ‘Sponge Park’” to learn more about the sponge park concept and its place within Quebec’s provincial approach to nature-based stormwater management.

ABOUT THE AUTHOR
Justin Jacques is editor of Stormwater Report and a staff member of the Water Environment Federation (WEF). In addition to writing for WEF’s online publications, he also contributes to Water Environment & Technology magazine. Contact him at jjacques@wef.org.