According to a Stanford research study, exacerbating rainfall owing to climate change has caused flood damages worth USD75 billion from 1991-2021 in the USA. Intensifying precipitation events, riverine flooding, and storm surge due to rising global temperatures are leading to rapid environmental depletion and putting homeowners, builders, banks, and insurers at grave financial risk. More than 4 million houses and small apartment buildings, especially concentrated on the coasts are vulnerable to high tide flooding from heavy torrential rains and frequent hurricanes.

Extreme weather conditions are expected to cause around USD32 billion of flood damage to at-risk USA homes by 2051, as per the report published by New York-based flood research non-profit First Street Foundation. Besides, expanding impervious surfaces such as pavements and roofs in cities and suburban areas are unable to naturally soak water, leading to flooding, erosion, turbidity (or muddiness), storm, and sanitary sewer system overflow, and infrastructure damage. Impervious surfaces tend to facilitate five times more runoff during urban flooding than natural land of the same size. 

The USA Environmental Protection Agency announced a grant funding of USD56 billion for prioritizing federal spending on upgrading and modernizing wastewater, stormwater, and drinking systems in the USA. The funding will also support public health, address sewer overflows, reduce pollution, and enhance the nation’s waterways. In the USA, much of the wastewater infrastructure is old and underfunded. In fact, 15% of the country’s 16,000 treatment plants supersede their design capacities and become stressed during extreme water conditions. Besides, urban stormwater is the primary source of impairment for 13% of assessed rivers, 32% of estuaries, and 18% of lakes. 

From motor oil used in vehicles to detergents used for washing away pavements, chemicals utilized in industrial sites to construction debris, all reach into the water bodies through city drains without undergoing treatment. The untreated water carries harmful pollutants such as pesticides, bacteria, and chemicals, fast food wrappers, cigarette butts, Styrofoam cups, etc. Thus, stormwater pollution affects water quality, exposing people to toxic contaminants and wiping off aquatic life.

Decreased infiltration and increased runoff creates a need for a proper stormwater management solution. Groundwater recharge is also a crucial part of stormwater management to replenish drinking water supplies and reduce the overall volume of runoff. Stormwater management utilizing green infrastructure practices such as rain gardens, permeable pavements, infiltration planters, stormwater tree trench, green roof, stormwater bumpout, swale, tree boxes, and rainwater harvesting systems can lead to the restoration of natural landscapes.

Green stormwater infrastructure 

·         Rain Gardens 

As per the Environmental Protection Agency (EPA), pollutants carried by rainwater runoff account for 70% of overall water contamination. Planted with grasses and flowering perennials and designed to hold and soak in rainwater, rain gardens are a cost-effective way to reduce runoff and reduce localized flooding. Compared to conventional lawns, rain gardens can remove up to 90% of nutrients and chemicals while allowing 30% of water to soak into the ground. A contingent of DTE Energy employees has planned to plant 20,000 sq. ft. of rain gardens in Plymouth, with a capacity to absorb around 225,000 gallons of water per rainstorm. The Milwaukee district has so far invested USD400 million on flood management programs to prevent water from flooding into the sewers.

·         Permeable Pavements

The new USD1.2-trillion infrastructure bill is aimed at installing “cool” pavements and boost tree canopies, which could prevent urban flooding on a large scale. The legislation allows states and local governments a grant of USD15 million to construct porous pavements, especially in disadvantaged areas. Constructed from porous material, permeable pavement allows rainwater to pass through it into the ground below, thus preventing the accumulation of rainwater in urban environments. Besides providing environmental benefits, permeable pavements eliminate the cost for retention basins and other water installations. 

·         Green Roofs

Green roofs are being widely employed in the USA cities such as Washington DC, Chicago, and Portland. Green roofs have a layer of plant material that has the capacity to soak 70% of rainfall over a given time. Although green roofs are initially expensive, they can reduce energy costs and cool overheated cities. Chicago has the maximum number of green roofs than any other city in the USA, and additional 600 projects are underway to cover almost 7 million sq. ft. city with green roofs. The city of Portland in Oregon provides grants of USD5 per sq. ft. for installing green roofs and aims to reduce its stormwater burden by 3 billion gallons with “eco-roofs”. 

Emerging Technologies for Stormwater Management

The American Society of Civil Engineers has stated a need for an investment of worth USD1 trillion to enhance the stormwater infrastructure for meeting future demands. The USA based startup, AquiPor Technologies is developing an innovative “pavement-like” permeable surface technology to help cities tackle urban flooding and stormwater runoff. The construction material allows high volumes of rainfall to flow through it and recharge the natural water cycle. The patented material surpasses traditional permeable pavement with the ability to filter out harmful pollutants and particulates on its surface. The sub-micron porosity allows clean water to flow into the ground and thus provide a low-maintenance and more scalable approach to stormwater management for years to come. 

Aqua-Swirl Stormwater Treatment System engineered for flow-through tends to eliminate pollutants from the contaminated water. The modular high-flow rate treatment system functions under gravity flow conditions utilizing hydrodynamic separation technology. The compact design of Aqua-Swirl integrated with lightweight and durable materials reduces the requirement of installing heavy lifting equipment for managing stormwater. 

Automated Outlet Structure (AOS) technology developed by a USA-based start-up is a patented intelligent device that mimics natural runoff rate and volume while providing proper management of water quality and quantity. While natural land allows 20% stormwater runoff, AOS technology controls runoffs during a rain event. The device has the ability to reduce stormwater runoff up to 50%, saving the customer substantial costs in underground detention. The intelligent stormwater management solution also sends storm event alerts and vital information about the device via cellular connectivity. 

DuroMaxx Steel-reinforced Polyethylene (SRPE) pipes available in various diameters as wide as 120’’ are constructed with 80 ksi steel and HDB-rated (hydrostatic design basis) polyethylene plastic. The SRPE pipe is durable and is engineered for carrying out municipal wastewater, irrigation water, storm sewer, and other highly critical and challenging applications across the USA.

Continuous Monitoring and Adaptive Control (CMAC) are innovative solutions to enhance the performance and efficiency of the existing stormwater infrastructure. The CMAC systems are adaptive and engineered to transform stormwater infrastructure into an asset, rather than a liability. CMAC integrates information from field-deployed sensors and telemetry-enabled control panels to provide accurate data for predicting weather events. Besides, CMAC reduces recurring costs and aids in accomplishing sustainable performance while meeting stormwater management outcomes. The real-time monitoring system can predict future scenarios utilizing the historical trends in an area. 

Conclusion 

Managing stormwater is one of the biggest and most expensive challenges for the USA, owing to the rising number of environmental disasters arising from climatic change. Besides, the rapid urban flooding needs to be addressed utilizing modern technologies. Green infrastructure systems, which are 5-30% less costly to construct than the traditional infrastructure can help to manage stormwater by preventing it to flow through sewers. Besides, the growing number of initiatives and programmatic funding for proper stormwater management practices can result in environmental and economic benefits.  

According to TechSci research report on “Global Stormwater Management Market By Tool (Grassed Swales, Rain Gardens, Pervious Pavement, Green Roofs and Others), By Application (Municipal, Commercial and Industrial), By End User Industry (Infrastructure, Education, Healthcare, Retail, Others) By Region, Competition Forecast & Opportunities, 2016-2026”, the global stormwater management market was valued at USD13.43 billion in 2020 and is expected to grow at a CAGR of 8.40% during the forecast period. The growth can be attributed to the increasing incidences of intense floods and storms along with rapid urbanization activities across the globe. Besides, technological advancements and growing investments towards water infrastructure and management systems are expected to propel stormwater management market.

According to another TechSci research report on “United States Stormwater Management Market By Tool (Grassed Swales, Rain Gardens, Pervious Pavement, Green Roofs and Others), By Application (Municipal, Commercial and Industrial), Competition Forecast & Opportunities, 2013 – 2023”, United States stormwater management market is expected to register a formidable CAGR and reach USD7.9 billion during the forecast period. The growth can be attributed to the rising storm incidences and development of innovative and smart technologies for stormwater management. Additionally, government initiatives such as Stormwater Grant Program (SWGP) and introduction of new standards such as Construction General Permit for the discharge of stormwater are expected to propel stormwater management market.