The Ballona Creek Trash Interceptor 007 is the first device of its kind in the U.S. It was developed and deployed by Dutch nonprofit The Ocean Cleanup (Delft). The Ocean Cleanup chooses strategic sites around the world to deploy their fully automated devices at no cost to the municipalities that host them. The devices clear debris from stormwater runoff and other sources before they reach the ocean. Similar devices are already operating in a growing number of marine-debris hotspots around the world, including sites in Indonesia, Guatemala, Vietnam, and Malaysia.

The Ballona Creek Trash Interceptor’s first storm season was marked by unprecedented runoff volumes generated by at least 12 atmospheric river storms as well as the strongest tornado to affect Los Angeles in 30 years.

“Its performance has exceeded our wildest expectations,” Boyan Slat told the Los Angeles Times in May. Slat is founder and chief executive of The Ocean Cleanup.

Simple, Sustainable Source Control

The Ballona Creek Trash Interceptor 007 floats just offshore from Ballona Creek’s discharge point, appearing as a wide, blue-and-white barge. It is moored to the north and south jetties of the channel and equipped with a purpose-built river monitoring system that sets the device in motion when stream conditions and weather forecasts suggest higher-than-usual flows. When it senses oncoming discharges, the solar-powered interceptor autonomously deploys two long, floating barriers in a V-shaped formation toward the shore.

Debris entering the Santa Monica Bay from Ballona Creek becomes trapped between the barriers, which gradually feed the trash into the opening of the device. A conveyor belt then guides the waste into six large, onboard dumpsters for periodic collection and proper disposal by DPW crews.  

As part of its arrangement with The Ocean Cleanup, DPW pays to perform basic maintenance and ensure timely disposal of collected debris. However, DPW describes on its website that these additional staffing concerns do not entail higher burdens on taxpayers, as Los Angeles County’s existing stormwater fee as well as support from environmental nonprofit groups fully fund the device’s upkeep. The Ocean Cleanup paid to deliver, install, and initiate the device in October 2022, beginning a 2-year pilot program to gauge its performance. During this trial period — after which DWP will have the option to assume ownership of the device at no cost — The Ocean Cleanup maintains ownership of the interceptor.

Although the device exceeded expectations during its first storm season in Los Angeles, the inaugural stretch was not without its challenges. At least twice — once in January and again in May — heavy winds and strong waves during intense storm events damaged the device’s deployable barriers, prompting project partners to secure replacements. However, by repositioning itself, the device remained semi-functional even during these outages.

Placement is Paramount

Located in southwestern Los Angeles, the 14-km (8.5-mi) Ballona Creek is among the most urbanized U.S. streams.

The channel sits within a 335-km² (130-mi²) watershed encompassing much of Los Angeles as well as Beverly Hills, Santa Monica, Culver City, and unincorporated Los Angeles County. The channel receives flows from an area with a combined population of approximately 1.5 million residents. A single storm-drain network serves the entire watershed, which collects runoff and debris from busy roadways and discharges it into Ballona Creek. According to DPW estimates, in an average year, heavy storms that overwhelm the drainage network send nearly 13,500 kg (30,000 lb) of plastic waste alone into Santa Monica Bay.

The Ocean Cleanup describes on its website that Ballona Creek represented an ideal site for a trash interceptor not only due to its debris output, but also its proximity to the North Pacific Subtropical Convergence Zone. This system of fast-moving ocean currents mixes nearshore waters with those hundreds of miles away from land, making trash and debris from Los Angeles and its surroundings particularly difficult to recapture after its discharge. Much of this waste from urbanized areas bordering the Pacific Ocean eventually concentrates in the Great Pacific Garbage Patch, a massive gyre of degraded but persistent microplastics covering approximately 1.6 million km² (620,000 mi²) of the ocean as of 2018.

Learn more about the Ballona Creek Trash Interceptor 007 project at the DPW website.

Top image courtesy of The Ocean Cleanup

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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.

The post ‘Interceptor’ Keeps More Than 75 Tons of Debris Out of Pacific Ocean appeared first on Stormwater Report.

This need is perhaps greatest for rivers running through cities, which are uniquely sensitive to “urban stream syndrome” — rapid deterioration in response to urbanization and economic development. As approximately 80% of the U.S. population and rising now lives in cities, buy-in from residents near urban streams is often a make-or-break factor in fundraising for restoration projects.

A recent study published in the Proceedings of the National Academy of Sciences proposes a new methodology to help quantify the financial value that locals attach to water quality improvements in urban streams. The study, supported by a U.S. Environmental Protection Agency (EPA) grant, aims to provide new tools to help governments and regulators of all sizes and scopes make better-informed decisions about the restoration projects they propose.

“Urban streams are ubiquitous and face a number of stressors from rapid economic development,” said study co-author Roger von Haefen, North Carolina State University (Raleigh) Professor of Agricultural Economics, in a release. “But there have not been well-established tools to help agencies assess the benefits of regulations aimed at improving the water quality of these streams.”

Translating Data Into Visible Outcomes

The research team focused on the Piedmont Region to prove and refine their new approach. This region stretches approximately 171,000 km² (66,000 mi²) between Maryland and Alabama. The Piedmont Region contains roughly 16,000 km (10,000 mi) of urban streams. Several Piedmont cities — most notably in North Carolina — are amid historic booms in population and rapid urbanization, causing new stressors on nearby streams.

One example is the Upper Neuse River Basin, which contains the cities of Raleigh and Durham. This region is projected to nearly double in population within the next few decades.

Considering the unique hydrological and socioeconomic conditions of the Upper Neuse River Basin and its residents, the researchers developed a three-part approach to gauge residents’ willingness to pay for different stream-restoration scenarios.

First, researchers compiled a robust set of water quality monitoring data from urban streams across the basin to capture a snapshot of their current quality. They input this data into a computer model that then calculated six water quality indicators for each stream: biodiversity, fecal coliform contents, specific conductance, total nitrogen, total phosphorus, and turbidity.

Recognizing that the average water customer will require more context to understand the meaning of these indicators, the second step saw the researchers consult with various environmental and public health experts familiar with the Piedmont Region to translate raw numbers into visible, easily understandable benefits. This translation effort followed strict procedural controls and quality control standards. It tied hypothetical improvements for each water quality indicator to observable outcomes. For example, a restoration project that would lower a stream’s fecal coliform, nitrogen, and phosphorus contents by specific thresholds could change the stream’s risks to human health from “medium” to “low”, while a project targeting turbidity could reduce the annual number of murky water days in the stream by a proportionate number.

Lastly, the researchers used these translations to conduct a voluntary, online survey of more than 2,500 households served by streams in the Upper Neuse River Basin. The survey proposed four hypothetical stream restoration projects, each promising observable changes in the condition of the stream ecosystem, risks to human health, and/or the annual number of murky days each stream would experience. Scenarios prescribed a range of different cleanup tactics or combinations thereof, such as increasing canopy cover along stream banks, introducing stormwater runoff source-control features, or repairing leak-prone collection systems. Each scenario entailed some degree of increase in monthly water bills via a new stormwater fee. Mimicking a referendum on whether to proceed with each hypothetical restoration project, respondents could choose to either approve or decline each scenario. 

Financial Insights at All Scales

Working from survey results, the researchers gained several insights into specific outcomes from stream restoration projects that locals prioritize and desire.

Most notably, the study describes, residents expressed far more interest in the health and safety of local streams (measured in biodiversity and risks to human health) than in their aesthetic value (the stream’s annual number of murky days). More than 85% of respondents ranked the water’s visual clarity as their least important concern, with stream health and human health roughly tied for their most important concern.

Answers for each scenario shed light on the types of projects residents would be most likely to support. For example, the most commonly approved proposal would increase tree cover along stream banks by 25% while also substantially decreasing runoff from nearby streets and parking lots. On average, each household was willing to pay $127 per year for such a project — approximately $54 million annually when aggregated according to the region’s rate-paying population.

Von Haefen described that although the hydrological and socioeconomic data underpinning this study were tailored narrowly to the Piedmont Region, a similar methodology could suit this type of analysis elsewhere. The authors expressed hope that their procedure will help guide decision-making at all levels, from small cities trying to implement cost-effective projects to federal regulators attempting to create more impactful water quality policies.

“We’ve shown that this approach can work, and it is designed for use in urban areas throughout the Piedmont Region,” von Haefen said. “Currently, EPA has limited tools to assess the benefits associated with environmental regulations that affect urban streams. We’re optimistic that federal and state agencies can use this framework to better capture those benefits and make more informed regulatory decisions.”

Read the full study, “Estimating the Benefits of Stream Water Quality Improvements in Urbanizing Watersheds: An Ecological Production Function Approach,” in the Proceedings of the National Academy of Sciences.

Top image courtesy of pakawoot/Pixabay

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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.

The post Researchers Pinpoint Financial Value of Urban Stream Restoration appeared first on Stormwater Report.

Wetland connectivity — the degree to which water from wetlands flows into nearby rivers, lakes, and oceans — is gaining increasing attention among scientists as one of the most important factors that determine the type and level of ecosystem benefits wetlands provide. However, determining whether wetlands connect to other freshwater systems can be difficult. For example, water from wetlands may flow into other bodies from either above or deep below ground-level, for only certain parts of each year, or only in instances of heavy rainfall. 

To help watershed managers, conservationists, and regulators make better-informed decisions about wetlands, a research partnership led by the U.S. Environmental Protection Agency (EPA) has developed the first-ever classification system to help assess different levels of wetland connectivity. A study published in the journal Nature Water introduces the system and applies it across the contiguous U.S. This system identifies where different types of wetlands exist as well as how their varying levels of connectivity affect local water quality.

“We still have much to learn about how wetlands connect to downstream waters in different geographic regions,” said Mark Rains, University of South Florida (Tampa) Geologist and study co-author, in a release. “This classification system gives us a place to start.”

Classification Improves Strategic Wetland Management

Using existing geospatial data on U.S. wetland coverage and hydrology, researchers identified four major wetland classes. These are based on their surface connectivity to downstream waters and their resulting effects on downstream water quality: riparian; non-riparian shallow (NRS); non-riparian mid-depth (NRMD); and non-riparian deep (NRD).

Riparian wetlands, defined as those that directly adjoin rivers and streams with multiple, aboveground connections, were by far the most commonly identified class in the U.S. These types of wetlands cover about 3.8% of all land area in the lower 48 states and have large effects on downstream water quality. Although the researchers confirmed that riparian wetlands are the most effective for controlling sedimentation, the study describes that they also tend to increase acidification and brownification — negative changes in water color due to high amounts of dissolved organic matter and carbon. 

By contrast, NRS wetlands were the rarest wetland class. NRS wetlands are concentrated in Florida and along the Atlantic coast. Featuring slightly less connectivity than riparian wetlands, these landforms contain permeable but poorly draining soils. They most often connect to downstream waters through aboveground connections, but this connection is not constant. NRS wetlands have the capacity for below-ground flows, but they tend to be shallow and infrequent, the study describes.

Water drains through the soil of NRMD wetlands more easily than NRS wetlands, making below-ground flows far more common than surface flows. They are considered less connected to downstream waters than riparian or NRS wetlands, yet still better-connected than NRD wetlands, which feature exclusively sub-surface flows and only experience above-ground flows during the most torrential downpours. Each of the three non-riparian wetland classes covered roughly 0.5% of total land area in the contiguous U.S.

The study reveals specific insights into how each class of wetlands affects downstream waters, measured by their influence on 11 criteria of stream water quality. They also map the locations of each class of wetlands across the U.S. to help regulators and watershed managers plan wetland restoration and protection efforts. Researchers illustrate how restoring different types of wetlands can help achieve specific goals for downstream waters. For example, the study describes that restoring NRD wetlands can often provide similar rates of nitrate removal and total suspended solids filtration as can restoring the same volume of riparian wetlands, but with the added bonus of minimizing acidification and brownification rates.

The classification system proposed in the study is globally applicable, researchers describe. EPA plans to make the system, as well as details on how to apply it, publicly available online, according to EPA Research Ecologist and lead author Scott Leibowitz.

“Until now, there hasn’t been a way to classify how wetlands connect to other waters at large scales,” said Leibowitz. “This has limited our ability to understand how wetland connectivity might contribute to water quality in watersheds.”

Read the full study, “National Hydrologic Connectivity Classification Links Wetlands with Stream Water Quality,” in Nature Water.

Vital Ecosystems Under Threat

The U.S. National Oceanic and Atmospheric Administration estimates that approximately 2,600 km² (1,000 mi²) of wetlands were lost in the U.S. between 1996 and 2016, mainly due to human development.

The U.S. Clean Water Act affords protections against development to waterways considered ‘Waters of the U.S.’ (WOTUS) — however, the definition of WOTUS has been ambiguous and subject to various changes since the concept’s introduction in the 1980s. Under the Clean Water Act, protections for wetlands have historically depended upon their ability to impair the quality of other WOTUS, such as navigable rivers and lakes, if degraded or removed.

How EPA gauges this potential, however, has also been the subject of various legal challenges, and ultimately hinges on the definition of wetland connectivity. In general, wetlands have received WOTUS status so long as they are adjacent to other protected waters, even if separated by dikes, barriers, or berms.

On May 25, 2023, the U.S. Supreme Court ruled 5-4 that Clean Water Act protections for wetlands extended to only those systems “with a continuous surface connection to bodies that are waters of the United States in their own rights”. Under the newly developed wetland connectivity classification system, this ruling means that only riparian wetlands would qualify for WOTUS status — and even then, only if they connect to other protected waters.

Image courtesy of Jose Sabino/Pixabay

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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.

The post New Classification System Focuses on Wetland Connectivity appeared first on Stormwater Report.

A recent study published in Nature Communications Earth and Environment analyzes how the topics discussed among Australian stream management professionals have shifted during the last 25 years. It probes these long-term changes using a unique dataset: nearly 1,000 peer-reviewed papers presented during the biennial Australian Stream Management Conference (ASMC) since 1996.

Lead author and University of Melbourne Research Fellow Kathryn Russell acknowledges that papers presented at conferences do not typically have the same scientific impact as research papers published in journals. However, she describes that because conference papers are often written by practitioners and public officials in addition to academics, studying these peer-to-peer exchanges can provide richer insights into the innerworkings of an industry than studying papers published in research journals. Understanding how environmental industries set priorities and promote specific practices among themselves can be useful. These behaviors directly affect the types of projects and policies these professionals pursue, the study describes.

“While our analysis is local, our recommendations are global,” Russell said in a release. These insights can help as environmentalists in Australia and beyond work to meet ecosystem restoration goals set by the United Nations.

Analyzing the Who, What, and How

Researchers focused their analysis on three distinct aspects of how Australia’s stream restoration industry has developed. They looked at who shares information, what topics they deem worthy of discussion, and how those topics are contextualized. The researchers developed a structured review process to assess these factors for 958 ASMC papers.

Since 1996, the authorship teams behind ASMC papers have grown markedly in both volume and diversity, the researchers found. The study notes that longer author lists for each paper suggest a growing emphasis on collaboration and circumventing jurisdictional boundaries. More authors also typically mean including people from different types of institutions and disciplines. Notably, the analysis found that participation by consultants has increased dramatically while contributions from academics have declined. This signals a shift in the stream management sector toward practice rather than theory. Recent decades have also seen an increase in the number of female authors, constituting 18% of all authors in 1996 and 37% in 2021.

Likewise, the content discussed in ASMC papers has become increasingly diverse. Researchers identified and tracked 60 distinct topics within the realm of stream restoration discussed in conference proceedings and measured the change in prevalence over time. Since 1996, the topics that have increased in popularity most consistently include large-scale waterway management programs and managing water associated with mining activities, with such topics as urban stormwater management, managing rivers on indigenous lands, and macroinvertebrate management also experiencing a steady uptick in prevalence. Particularly in more recent years, an increasing number of papers have discussed such topics as citizen science, environmental DNA, and remote sensing.  

Evidence suggests that much of the discourse conducted via ASMC proceedings responds directly to high-profile natural events that affect rivers and streams, such as droughts, floods, and bushfires. For example, Australia’s Millennium Drought from 1996 through 2009 generated a spike in discussion about policy options to counteract water scarcity and stream overallocation. In 2010, the topical distribution shifted quickly toward flood management when the La Niña system caused spates of severe flooding across Australia through 2012.

But perhaps most telling, the researchers describe, is what ASMC papers do not discuss. According to the study, most ASMC proceedings that detail specific projects and policies focus on successes, but very few report lessons learned from failures. For that reason, researchers claim that much of Australia’s environmental sector champions a reactive rather than proactive approach to stream management. Although adaptive management topics have been included within the ASMC program since 1996, several crucial subtopics to an effective adaptive management strategy, such as vision-setting and project prioritization, have not been substantially discussed.

Global Insights from Local Investigation

The United Nations Sustainable Development Goals (SDGs) specify several worldwide targets for freshwater ecosystem restoration by 2030. The researchers argue in the study that conferences and industry events can encourage progress toward these targets by prioritizing certain topics in the papers they accept. The study outlines several broad recommendations specifically tailored to the SDGs to help drive sustainable stream restoration regardless of region.

First, program-makers should strive to approve papers that represent efforts from a variety of different professional backgrounds as well as diverse demographics. This not only includes a mixture of practitioners, policymakers, and academics among authors, the researchers describe, but also papers describing projects that involve and affect indigenous and socially disadvantaged populations.

Researchers also call for a greater emphasis on green infrastructure and nature-based solutions in knowledge-sharing efforts. Authors acknowledge that these topics are growing in prominence elsewhere, such as in Western Europe and North America, but that they still generally lag in Australia.

Conference programs should promote guidance on how stream management programs can become more adaptive. This includes spotlighting failed programs as well as successful ones. It also may include information about monitoring systems and how to incorporate insights into these systems to improve broader waterway management programs.

Read the full study, “Evolution of a River Management Industry in Australia Reveals Meandering Pathway to 2030 UN Goals,” in Nature Communications Earth and Environment.

Top image courtesy of Pixabay

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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.

The post Conference Papers Offer Glimpse into Evolution of Stream Management Sector appeared first on Stormwater Report.

The city’s approach prescribes a range of investments in the coming years that focus on both infrastructure and information. These steps are detailed in an action plan released by the New York City Department of Environmental Protection (NYC DEP) in September 2022.

In January 2023, the city announced major expansions to two stormwater initiatives intended to enhance resilience in all five boroughs: the Cloudburst Program and the FloodNet system.

• The Cloudburst Program, developed in partnership with the City of Copenhagen, Denmark, constructs neighborhood-scale clusters of green and gray infrastructure that cooperate to convey runoff to strategic points during major storms. The program will receive an additional USD $400 million to support projects in four new neighborhoods.
• FloodNet, a system of real-time flood-monitoring sensors already active in all five New York City boroughs, will receive an additional USD $7.2 million that will enable the network to multiply its current number of sensors by a factor of 15.

Cooperation on ‘Cloudburst’ Control

Roughly 60% of New York City is served by combined sewer systems that convey both wastewater and stormwater, according to NYC DEP estimates. Particularly in densely urbanized, inner-city neighborhoods served by combined sewer systems, heavy storms frequently overwhelm the collection systems that are already overburdened by a high concentration of residents, causing chronic flash flooding.

In Copenhagen, stormwater professionals often refer to the short, intense surges of rainfall that most commonly cause flash flooding and combined sewer overflows (CSOs) as cloudbursts. During the last few decades, Copenhagen has demonstrated success in using ambitious, extensive, and unconventional infrastructure designs to control cloudbursts. The city’s approach not only includes traditional elements like rain gardens and bioretention cells, but also subsurface pipe systems, restored urban wetlands, and even entire streets rebuilt with slopes and curves meant to convey runoff to specific points. These green and gray features work in tandem to relieve burdens on combined sewer systems on the neighborhood scale, while also providing new, attractive community amenities.

Seeking to learn from Copenhagen’s experience, NYC DEP formed a partnership with Copenhagen-based engineering firm Ramboll in 2016 to identify opportunities for similar projects in New York City. The partnership published a study about their findings in 2017, identifying a site in Queens’ South Jamaica neighborhood as the best candidate for a pilot project.

After a lengthy design process, construction on the site will begin this year, New York City Mayor Eric Adams announced in September 2022. The initiative, which marks the official commencement of New York City’s Cloudburst Program, will invest up to USD $5 million in South Jamaica to channel stormwater from around the neighborhood toward two open, grassy areas, which will themselves receive new vegetation and subsurface features to increase their temporary storage capacity. Plans also call for the reconstruction of an existing basketball court at a lower, sunken elevation, which will provide additional detention capacity during cloudbursts. In all, NYC DEP expects the new features to increase local stormwater management capacity by approximately 1.1 million L (300,000 gal) — designed to eliminate flooding from today’s definition of a 100-year storm.

Under the Cloudburst Program, the design process is already underway for similar renovations targeting the St. Albans neighborhood in Queens as well as Manhattan’s East Harlem neighborhood. The newly allocated USD $400 million in municipal and federal funds, which Adams announced in January 2023, will enable the city to initiate the design process for four additional neighborhoods: Corona Park (Queens), Kissena Park (Queens), Parkchester (Bronx), and East New York (Brooklyn). NYC DEP expects construction in these neighborhoods to begin in 2025. More than two dozen additional neighborhoods are under consideration by NYC DEP for future projects, Adams described.

“This $400 million investment in stormwater management projects cement New York City’s status as a national and global leader in green infrastructure and shows our commitment to protecting New Yorkers from disastrous floods,” Adams said in a January release.

Casting a Wider FloodNet

In addition to socioeconomic and environmental justice concerns, a key factor in Cloudburst’s site-selection process is flooding data.

How often and how severely a neighborhood has historically experienced flooding, the location and frequency of existing flooding, and how those trends are poised to shift as climate change intensifies are all factors. To better provide this data, the City University of New York (CUNY), New York University (NYU), Brooklyn College, and the Science and Resilience Institute at Jamaica Bay partnered with various municipal agencies to introduce the FloodNet system in 2020.

FloodNet partners install water-level sensors in strategic locations throughout the city. Each sensor is about 3 m (10 ft) from the ground and feeds real-time information on the timing and severity of flood events to a publicly accessible dashboard. The dashboard provides users remote access to minute-by-minute updates on floodwater depths as they change. The sensors also can discern whether the flood results from CSOs and overburdened storm drains or coastal storm surges, as well as how developing floods compare to historical events.

Users can explore, for example, the details of how Hurricane Ida caused record-breaking flooding in Brooklyn in September 2021, or how a new-moon tide compounded the effects of a winter storm in December 2022 to cause substantial coastal flooding in the Far Rockaway neighborhood of Queens.

Currently, FloodNet consists of 31 sensors. That number is already rising thanks to USD $7.2 million in new municipal funding announced in January. This funding will increase the number of monitored locations to 500 during the next 5 years. Network expansion already is underway, with the first new sensors installed in Staten Island scheduled to come online shortly.

“The city’s increased investment in FloodNet sensors will create an even more expansive, hyperlocal monitoring network that can alert New Yorkers in real time to dangerous flooding caused by intense rainfall,” New York City Chief Climate Officer and DEP Commissioner Rohit T. Aggarwala said in January. “This life-saving, innovative technology will help us better understand and prepare for future storms, plan and build more resilient communities, and design and implement infrastructure that will more effectively manage extreme weather.”

Top image courtesy of Alanna21/Pixabay

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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.

The post New York City Earmarks $400 Million For Flood Infrastructure, Information appeared first on Stormwater Report.

The Las Vegas Valley provides one example of this situation. A recent study published in the Journal of Hydrometeorology examines 70 years of flooding data as they relate to long-term changes in temperature, population, infrastructure, and land use. The study not only suggests that Las Vegas flood events are becoming more severe gradually, but also that the timing of “flood season” is shifting from summer to winter.

The study was written by researchers from the Desert Research Institute (DRI; Las Vegas), University of Wisconsin–Madison, Guangdong University of Technology (Guangzhou, China), and Clark County Regional Flood Control District (Las Vegas).

“A lot of research focuses on a single factor — either land use or climate — but in Las Vegas, our study shows that both are changing and interacting with each other,” said Guo Yu, DRI Hydrologist and lead author, in a release. “I wanted to understand the reason for this change as well as the physical mechanisms driving it, because that will help water managers and the public understand whether such a change will continue in the future, given climate and land-use changes here.”

An Unlikely Hotspot for Flooding

The Las Vegas Valley typically receives only about 10 cm (4 in.) of precipitation each year — about 87% lower than the nationwide average. Despite its aridness, the region is a hotspot for severe flood events. When the North American Monsoon system passes through the southwest U.S. in the summer months, storms tend to deliver short yet intense bursts of rain that fall on slow-draining, sandy, and vegetation-sparse surfaces that generate large amounts of runoff.

Meanwhile, the Las Vegas metropolitan area remains in the midst of one of the most dramatic population booms in the U.S. In 1950, the city contained fewer than 35,000 people. According to the 2020 U.S. Census, that number now approaches 3 million. This rapid urbanization has spurred a steady expansion of impervious space in the Las Vegas Valley and sprawling into surrounding mountain ranges.

For these reasons, the valley is highly susceptible to flash flooding. In terms of streamflow volume per unit of watershed area, the researchers note, five out of twelve of the most extreme flash-flood events on record throughout the U.S. have occurred in the southwest U.S. Fatal flooding has occurred as recently as August 2022, when monsoon-driven rains in southern Nevada caused two deaths.

Climate Change, Urbanization Change the Equation

From 1950 until the mid-1980s, the analysis finds that the average annual peak flow — in other words, the severity of the year’s largest flood event — was about 15 m³/s (530 ft³/s). During the second half of the study period, that average jumped to 89 m³/s (3143 ft³/s), despite average annual rainfall totals rising by only about 2 mm (0.08 in.).

Despite this increase in peak flows, an ever-expanding network of flood control infrastructure in the watershed works to keep most hazards away from populated areas. Since its establishment in 1985, the Clark County Regional Flood Control District has constructed more than 1000 km (620 mi) of storm drains, open channels, and culverts intended to divert runoff toward Lake Mead. This infrastructure tends to feature concrete lining, which keeps water moving toward a specific course, but also prevents infiltration and enhances peak flows outside city limits.

According to the study, on the watershed scale, this infrastructure has caused floodwater density in the Las Vegas Valley to more than double, potentially entailing hazards as the Las Vegas metropolitan area continues to expand outward.

Meanwhile, while climate change may not have increased overall rainfall volumes, evidence suggests that the timing of major storms in the southwest U.S. has shifted. From 1957 to 1988, 17 annual peak flows occurred in summer and 15 occurred in winter. From 1989 to 2020, 12 peak flows occurred in summer and 20 occurred in winter.

More than half of these wintertime peak flows resulted from atmospheric rivers — long, narrow bands of atmospheric water vapor capable of producing prolonged storms that most strongly affect areas at the foot of mountain ranges. The study suggests that climate change is gradually strengthening atmospheric river storms while weakening the North American Monsoon system.

Historically, monsoon-driven storms occurred more frequently, delivering less rainfall at a time. By contrast, atmospheric river storms occur less often, but deliver more precipitation at once, creating a higher potential for flooding.

“Historically, people in Las Vegas haven’t paid as much attention to winter floods as to summer floods,” Yu said. “But our research shows that there will be more frequent winter floods happening because of climate change. This is because the warmer sea surface temperatures on the Pacific coast will cause more atmospheric rivers, like what we’re seeing this January in California. And when these are positioned to bypass the Sierra Nevada mountains, they will very likely hit Las Vegas and cause severe winter rainfall and floods.”

The research pinpoints 1996 as a clear “changepoint” in the regime of flooding in the Las Vegas Valley. That year is when the effects of changing storm seasonality, urbanization, and flood-redirection infrastructure combined to a point where annual peak flows increased substantially and non-linearly compared to their historical averages. Within the 70-year study period, the nine largest peak flows observed occurred since 1996.

Read the full study, “The Nonstationary Flood Hydrology of an Urbanizing Arid Watershed,” in the Journal of Hydrometeorology.

Top image courtesy of zzim780/Pixabay

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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.

The post Why Las Vegas is Experiencing More Flooding Despite Stable Precipitation appeared first on Stormwater Report.

The new stretch of seepage barrier wall will work in tandem with other nearby infrastructure to restore the natural, southward course of water in Everglades National Park toward Florida Bay. Steady development between Lake Okeechobee and Florida Bay throughout the 20^th century has disrupted that natural course. The development has sent water to populated areas in other directions during heavy downpours while also impairing water quality, aquifer storage, and biodiversity in the Everglades ecosystem.

“This seepage wall is essential to keeping water in Everglades National Park while protecting adjacent neighborhoods,” Eric Eikenberg, CEO of The Everglades Foundation (Palmetto Bay, Florida), said in a release announcing the groundbreaking. “This feature will also allow us to send water south to Florida Bay where it belongs.”

Protecting the ‘8.5 Square Mile Area’

Where the Everglades meet the western border of Miami-Dade County, a low-lying, agricultural community known as the 8.5 Square Mile Area (8.5 SMA) sits within the path of least resistance for Everglades floodwaters. The community, prone to severe flooding since its settlement, is surrounded by a series of levees along its perimeter. However, because of the permeable soils on which the levees sit, water during heavy storms often seeps beneath them and causes nuisance flooding in the 8.5 SMA.

Early last fall, construction concluded on a 3.7-km (2.3-mi) stretch of seepage barrier wall beneath the L-357 Levee, which marks the northern border of the 8.5 SMA. According to SFWMD representatives, this initial phase of the seepage barrier wall project is already preventing stormwater flooding in the region it serves.

“We completed Phase I of this project in September [2022], and now just three months later, we are now breaking ground on the next phase that helps keep even more water in Everglades National Park,” said “Alligator Ron” Bergeron, SFWMD Governing Board Member, in a statement. “By keeping water in the park where it’s needed, water stays away from nearby neighborhoods. Thank you to our partners at the U.S. Army Corps of Engineers for working with us to expedite this project to benefit the global Everglades.”

According to project details from ACE, the seepage barrier wall segments now under construction will consist of a mixture of soil, cement, and bentonite slurry meant to minimize soil permeability with minimal effects on geological function. Each barrier will have an approximate thickness of 71 cm (28 in.) and run along the center of the L-357 Levee.

The seepage barrier wall is the latest effort under the auspices of the Central Everglades Planning Project (CEPP). This project is a long-term, interjurisdictional infrastructure campaign led by ACE and SFWMD that aims to send an additional 456 million m³ (370,000 ac-ft) of water per year through the Everglades and into the Atlantic Ocean.

Support From Tallahassee

The seepage wall is one of several infrastructure projects funded via Florida Executive Order 19-12, signed in January 2019 by Governor Ron DeSantis. Builders expect the wall extension effort to take approximately 2 years to complete.

Executive Order 19-12 allocated USD $2.5 billion in state funding toward Everglades restoration and associated water quality projects over 4 years. At the time, this was the largest investment in an environmental project in Florida’s history.

Another major CEPP initiative supported by Executive Order 19-12 is the Everglades Agricultural Area Storage Reservoir Project. The effort, which is underway now, includes construction of a 240,000-ac-ft reservoir that will collect excess water from Lake Okeechobee, supported by a 6,500-ac stormwater treatment area intended to protect water quality and discourage flooding. It also features a series of new canals and conveyance systems.

In January 2023, DeSantis signed Florida Executive Order 23-06. This order directs the Florida Department of Environmental Protection to allocate an annual USD $3.5 billion through 2026 toward additional Everglades water management projects. It also calls on SFWMD to expedite restoration projects previously authorized as part of CEPP and other long-term Everglades programs. 

Top image courtesy of South Florida Water Management District

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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.

The post Underground Barriers Rehabilitate Everglades, Block Floodwaters appeared first on Stormwater Report.

The Surface Water and Ocean Topography (SWOT) satellite will orbit Earth for approximately three years. In this mission, it will gather high-resolution data about annual fluctuations in ocean depths as well as the height of large lakes and rivers. From these measurements, scientists will be able to derive key metrics to understand the effects of climate change and the processes that drive flooding. Currently, this data originates mainly from water-level and tidal gauges — infrastructure that does not currently exist in the majority of Earth’s surface waters and coastlines, let alone in the deepest reaches of the ocean.

The SWOT mission is a product of about 15 years of planning between the U.S. National Aeronautics and Space Administration (NASA) and French Centre National d’Études Spatiales (CNES).

Tamlin Pavelsky, SWOT Science Team Lead, described that SWOT’s insights will “usher in a new golden age for the science of rivers and lakes.”

“Right now, we can measure how the amount of water in lakes and reservoirs changes for a few thousand lakes worldwide,” Pavelsky said. “With SWOT, we’ll be able to observe millions. As climate change and direct human activities influence our rivers, SWOT will help us to understand changing risks from flooding, opportunities for sustainable water use, and the fundamental nature of these important natural systems.”

Fathoming the Depths of Climate Change

Climatologists can infer an array of important details about how waterways behave in a warming world based on waterline fluctuations. In the case of rivers, analyzing long-term patterns in streamflow volume can help watershed managers better predict seasonal flooding and drought as well as the unique ways in which a specific reach of stream will respond to major precipitation.

Most predictive models that researchers and cities now use to predict flooding and drought rely on data from river gauges. In the few rivers where these gauges exist, many suffer from gaps in coverage that undermine effective flood and drought predictions. Lakes and reservoirs face similar issues, subject to gradual waterline fluctuations that can provide an early warning of drinking water shortages, recreational risks, and ecological impairments, if identified by monitoring equipment.

Researchers believe the world’s oceans absorb more than 90% of the excess heat and carbon trapped in the atmosphere by greenhouse gases, but a similar lack of worldwide tidal-gauge coverage has hindered attempts to explore this phenomenon in detail. Insights from SWOT, according to the mission team, will help scientists identify the points at which oceans reach their capacity to absorb this heat and carbon and release it back into the air. Understanding these thresholds — in ambient ocean currents as well as short-term features like fronts and eddies — will offer scientists a better picture of the ocean’s role in climate change and develop more accurate predictions of sea-level rise.

SWOT will focus mainly on waterways large enough to require extensive sensor coverage. This includes lakes covering areas larger than 6 ha (15 ac), rivers wider than 100 m (330 ft) in diameter, and the world’s coastlines, reports the mission team. Monitoring the Earth’s surface between the Arctic and Antarctic approximately every 21 days, the satellite will provide in-depth data on more than 95% of these important waterways worldwide.

“We’re eager to see SWOT in action,” said Karen St. Germain, NASA Earth Science Division director, in a release. “This satellite embodies how we are improving life on Earth through science and technological innovations. The data that innovation will provide is essential to better understanding how Earth’s air, water, and ecosystems interact – and how people can thrive on our changing planet.”

Taking a Worldwide Pulse

The key difference between SWOT and other satellite-based survey missions is its purpose-built technology. At the heart of the SWOT satellite is an instrument known as a Ka-band radar interferometer — KaRIn for short.

KaRIn works by bouncing long-range radar pulses off the water’s surface, using two specialized antennae to receive and interpret the return signal from each pulse. A single pulse can accurately measure water depth over an area covering approximately 50 km (30 mi) wide. As it slowly orbits the Earth measuring waterways pulse by pulse, the SWOT satellite will provide researchers with approximately one terabyte of hydrological data per day.

Immediately following SWOT’s launch on December 16, 2022, from California’s Vandenberg Space Force Base, it began a six-month “fast-sampling” phase. During this period, the satellite will hover about 857 km (532.5 mi) above Earth, circumnavigating the globe once each day to provide a baseline set of data intended to calibrate the equipment.

In 2019, NASA and CNES invited hydrologists and oceanographers to participate in this calibration campaign by providing local, on-the-ground water level measurements to validate via SWOT’s initial findings. After this phase, SWOT will ascend by about 34 km (21 mi) and dramatically slow its pace, marking the beginning of its main survey campaign.

“This mission marks the continuity of 30 years of collaboration between NASA and CNES in altimetry,” said Caroline Laurent, CNES Orbital Systems and Applications director, in a statement. “It shows how international collaboration can be achieved through a breakthrough mission that will help us better understand climate change and its effects around the world.”

Follow the SWOT mission’s progress on its website, and watch the satellite’s launch atop a SpaceX Falcon 9 rocket below:

Top image courtesy of U.S. National Aeronautics and Space Administration/Keegan Barber

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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.

The post Newly Launched Satellite Seeks Worldwide Waterway Visibility appeared first on Stormwater Report.

After the flooding dissipated, residents of the decimated town of Ahrweiler told the Associated Press that they received only minutes of notice that the flood was approaching and had little detail about its severity, due in part to the small community’s reliance on upstream river gauges as its primary warning system. These gauges measured water levels only once every 15 minutes — far too slow to capture an event developing as quickly as the Ahr Valley flood — and were quickly drowned and incapacitated as the river exponentially rose.

Geoscientists from the University of Göttingen (Germany) and University of Bonn (Germany) have been studying the Ahr Valley flood since it occurred, searching for untapped sources of information that could have bought residents of Ahrweiler and surrounding communities extra time to protect people and property. In a new study published in Geophysical Research Letters, they report an unconventional finding: Using data from stations intended to detect earthquakes could also provide earlier notice of severe flooding on the horizon.

Signals in the Sediment

In terms of the ways they affect the planet’s surface, major floods are not terribly different than earthquakes, the researchers write. Both phenomena typically transport huge amounts of sediment, for example. Additionally, just as earthquakes tend to distort the slope and orientation of the planet’s surface when they occur, the surface also often bows slightly under the immense weight of a large pool of floodwaters.

Given that no earthquakes occurred in the days leading up to the Ahr Valley flood, researchers sought to determine whether a seismometer station on the outskirts of Ahrweiler had picked up any indication that an event large enough to cause these types of disruptions was imminent. Focusing on the day of July 14, study authors pored over data on particle motion captured by the Ahrweiler seismometer every 30 seconds in search of abnormalities. They found that, as the Ahr Valley flood moved toward Ahrweiler in a winding path through the valley, the ambient seismic power of typical Ahr River flow modestly waxed and waned before shooting up quickly and suddenly from about 2 to 15 Hz at around 10 p.m. At that point, according to the study, the flood was still slightly more than hour away from Ahrweiler, but it had just entered the seismometer’s sensitivity range. At the same time, the seismometer picked up sudden drastic changes in the direction in which sediments were moving as a result of changes in the surface’s slope, a pattern that closely followed the arrangement of the Ahr River’s channel. In this way, the researchers were able to use the data to track the flood’s location in real-time.

Knowing the seismometer’s sensitivity range, its distance from the Ahr River, how the sudden increase in seismic power compared to its typical values, and the path of sediment movement as it changed, a series of calculations enabled the researchers to accurately determine the flood’s proximity, speed, and severity. The data also displayed subtle signals as the flood encountered — and broke through — large barriers such as bridges that were swept up in the flow to become damage-causing debris. Researchers managed to estimate debris contents based on momentary fluctuations in movement speed and the location of large structures along the river channel.

 “If the data stream from that station had been available and analyzed as our research now shows, essential, real-time information on the magnitude and velocity of the flood would have been available,” Michael Dietze, University of Göttingen geoscientist and lead author of the new study, said in a statement.

According to the study, data provided by the seismometer before the Ahr River flood could have offered roughly 30 minutes of extra notice to the residents of Ahrweiler than river gauges alone.

Prediction Potential

While these preliminary results are promising, study authors caution that using seismometers as a warning system for major floods is far from a perfect approach.

For one, as opposed to water-level sensors, they are highly sensitive to background noise that can distort readings and make it difficult to attribute fluctuations to floods with confidence. Researchers stipulate that seismometers will achieve their most useful flood-prediction data when they occupy a physical “sweet spot” — neither too close nor too far away — from a river channel and from where an event ultimately occurs. For another, while the Ahrweiler seismometer was far enough removed from the Ahr River channel to avoid being overwhelmed by the approaching flood, it was still susceptible to damage. Readings from the station suddenly ceased at 11:19 p.m. on July 14 when the flood took out its off-site power supply.

Under the current state of the science, interpreting seismometer data for flood prediction also requires significant human input. However, researchers describe that this analysis process could represent a suitable application for machine learning models that would help bridge the gap between raw data and useful insights more quickly.

Despite these weaknesses, researchers also describe that the approach has noteworthy strengths and can find uses far beyond Ahrweiler. The methods and algorithms described in the team’s study can be replicated in any river valley containing an appropriately sited seismometer so long as users have a baseline understanding of the local river’s normal behavior. If refined, the approach could be particularly useful for mountainous regions of Europe, Dietze described.

“As 10% of Europe’s surface area is prone to rapid flooding by rivers confined in valleys, we want to start thinking about new ways of flood early warning,” Dietze said. “The current network of water level stations is not enough to be adequately prepared for future events.”

According to one part of the team’s analysis, while outfitting this 10% of Europe with enough seismometers to constitute a comprehensive flood-warning system would be expensive, it would cost roughly 0.006% of the total cleanup costs associated with the Ahr Valley flood.

Read the full, open-access study, “A Seismic Approach to Flood Detection and Characterization in Upland Catchments,” in Geophysical Research Letters.

Top image courtesy of iStock by Getty Images

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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.

The post What Detecting Earthquakes Can Teach Us About Predicting Major Floods appeared first on Stormwater Report.

This month, Google unveiled FloodHub, a publicly accessible portal that enables users to detect riverine flooding up to a week in advance at parcel-scale resolution, showing precisely where rivers likely will overflow as well as how much flooding locals can expect. The technical work underpinning FloodHub has been underway since 2018, the company writes, beginning with coverage of India and Bangladesh and gradually scaling up to more countries. Today, FloodHub offers ongoing forecasts in 20 countries across Africa, Southeast Asia, and South America, with a goal to extend coverage worldwide, writes Yossi Matias, head of Google’s Crisis Response team.

“This expansion in geographic coverage is possible thanks to our recent breakthroughs in AI-based flood forecasting models,” Matias describes. “We’re committed to expanding to more countries.”

Forecasting With FloodHub

When Google formed partnerships with the Indian Central Water Commission and Bangladesh Water Development Board in 2018, the company sought to demonstrate that a machine-learning program trained on local river gauges could provide proactive and actionable flooding information to those living along the region’s major rivers. The product of this early work was a smartphone-based notification system that would give advance warning to any device with either Google Search or Google Maps installed if the program expected flooding based on shifting water levels and historical patterns.

In 2021, according to Matias, this notification system delivered 115 million flood alert notifications to 23 million people in India and Bangladesh. It also informed on-the-ground outreach efforts by community groups to those living in the region without Google-accessible devices.

However, the program’s reliance on river gauges not only limited the range of rivers on which it could be applied, but also provided only a maximum of 2-3 days of advance notice to locals. In recent years, Google describes, machine learning has become sophisticated enough to make functional, parcel-scale predictions incorporating weather forecasts in addition to river-gauge readings. In an August study about the new machine-learning approach at the foundation of FloodHub, Google researchers describe how incorporating weather forecasts from such sources as the U.S. National Aeronautics and Space Administration (NASA) and U.S. National Oceanic and Atmospheric Administration (NOAA) can yield accurate flood predictions up to a week in advance of a river overflow event as well as more reliably assess threats for river basins without expansive gauge networks.

With FloodHub, Google’s notification system has evolved into a visual and interactive format, appearing as an overlay of data gleaned from its machine-learning program on top of its popular Google Earth interface. At a glance, users can identify regions where flooding is likely according to a color-coded system of severity. They can then zoom in for more details on specific areas at risk and the likely timing of the event.

Data-Driven Stormwater Control

Other recent work by Google in the field of stormwater management has applied machine learning to disaster response after hurricanes as well as green infrastructure implementation.

In 2020, Google partnered with the United Nations World Food Program to introduce a new way to assess damages and prioritize relief efforts after a hurricane by using machine learning to quickly interpret satellite imagery. Particularly when hurricanes cause damages over a large area, disaster response professionals often undertake a manual process to pore through thousands of satellite images to assess the areas hit hardest, a process that typically takes days to complete. Google’s system, by contrast, analyzes satellite images to detect the boundaries of each specific property within a damaged area and compare the post-hurricane state of each parcel against the most recent pre-hurricane image available. It then applies an algorithm to determine which areas require the most urgent assistance, accelerating response times. As reported by Wired, the program was recently deployed in Florida in the wake of Hurricane Ian, where it helped aid groups coordinate relief payments.

While launching FloodHub, Google also announced plans to improve on its existing Tree Canopy Insights app. The app, based on the Google Earth engine, provides a neighborhood-by-neighborhood overlook of tree canopy coverage in 14 U.S. cities, offering this information alongside local climatic and socioeconomic data. By providing an accessible connection between canopy coverage and such factors as surface temperatures, population density, and median household income, the app aims to help urban planners pinpoint areas where planting new trees can make the most significant differences in residents’ quality of life, Matias describes. By the end of 2022, Google intends to expand the app’s coverage to “hundreds of cities,” the company announced in November.

Top image courtesy of PIRO/Pixabay

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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.

The post <strong>Google Takes on Flooding With Satellites, Machine Learning</strong> appeared first on Stormwater Report.