When rainfall hits an impervious surface, it meets whatever pollutants reside on that surface. The average city block can generate more than five times as much runoff as a forested area of equal size. In contrast, streets, parking lots, rooftops, and other hard, impervious (nonabsorbent) surfaces essentially repel stormwater, preventing it from soaking into the land and forcing it to flow whichever way gravity takes it. This is then gradually released into the groundwater, nearby water bodies, and the atmosphere. Porous natural landscapes, such as meadows and forests, will readily soak up most of the rain or snowmelt they receive. The more permeable (or absorbent) the surface, the less runoff there will be. Runoff, the product of rainstorms or snowstorms, flows over the ground and into drains, sewers, and waterways. Gray infrastructure also does not provide the same community benefits mentioned above. It does not provide the same range of benefits as green infrastructure since it neither reduces the amount of stormwater that reaches waterways nor, for the most part, improves the quality of that runoff. It relies on hard infrastructure-such as storm drains, concrete, and pipes-to collect and channel stormwater (sometimes treated, oftentimes not) into waterways. Gray infrastructure is the more traditional (and typically more expensive) water management systems that green infrastructure complements and can at times replace. It also increases the quality and quantity of local water supplies and provides myriad other environmental, economic, and health benefits-often in nature-starved urban areas. It mimics natural hydrological processes and uses natural elements such as soil and plants to turn rainfall into a resource instead of a waste. Green infrastructure captures the rain where it falls. In doing so, it cuts down on the amount of flooding and reduces the polluted runoff that reaches sewers, streams, rivers, lakes, and oceans. Green infrastructure encompasses a variety of water management practices, such as vegetated rooftops, roadside plantings, absorbent gardens, and other measures that capture, filter, and reduce stormwater. Here’s a look at what green infrastructure is, what it does, and why we should invest so much green paper in it. As an alternative to traditional water management systems, green infrastructure offers a cost-effective solution to many of our water woes, including how to handle flooding and stormwater pollution. The country’s urgent infrastructure needs also present a major opportunity. Environmental Protection Agency (EPA) estimates that upgrading our stormwater and other public wastewater systems will require at least $150 billion in investments over the next two decades. Not surprisingly, in 2021, the American Society of Civil Engineers bestowed a lowly D letter grade on U.S. In many urban and suburban areas, this runoff causes significant flooding as well. waterways from city sewer systems every year, polluting the environment and drinking water supplies. An estimated 10 trillion gallons of untreated stormwater runoff, containing everything from raw sewage to trash to toxins, enters U.S. ![]() The critical systems we rely on nationwide endure chronic overuse and underinvestment, including our stormwater management systems. ![]() ![]() From highways to bridges to airports, America’s infrastructure is in dire need of a face-lift.
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