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The most effective tools to reduce the water pollution and flooding caused by stormwater runoff are green infrastructure, land conservation, and best management practices on farms.
Stormwater runoff pollutes waterways and causes dangerous, damaging flooding. Nature-based stormwater management strategies allow the ground to absorb and filter stormwater, resulting in cleaner water and fewer, less severe floods.
Clean water and flood mitigation, in turn, provide a host of economic benefits. For example, clean water decreases water-treatment costs for communities and supports water activities like fishing and paddling that contribute $29 billion each year to the United States economy. Less frequent flooding saves communities billions of dollars in averted damage. Clean water also provides a host of environmental benefits (e.g., wildlife habitat) and health benefits (e.g., safe drinking water).
This guide outlines the three most effective nature-based stormwater management strategies—green infrastructure, land conservation, and best management practices (BMPs) on farms—and provides links to resources for each.
For resources focused on nature-based stormwater management more generally, see the Naturally Resilient Communities website.
The term “green infrastructure” refers to features such as rain gardens and bioswales that reduce runoff by using vegetation and soil to absorb and filter stormwater. (It also refers to tools like rain barrels that can store stormwater for reuse.) Green infrastructure is especially effective—and necessary—in built environments, where it can serve as a cost-effective complement to (and sometimes substitute for) conventional stormwater infrastructure like storm drains and pipes, which often carry pollutants directly into waterways and easily overload during severe storms.
Green infrastructure components can be included in the design of new projects or incorporated into existing streetscapes and landscapes. Often, green infrastructure makes cities and neighborhoods more colorful and interesting. Green infrastructure installations can also provide hands-on educational opportunities close to home, school, or work for people of all ages to learn about water, soil, and wildlife.
Follow the links for more detailed information about these different types of green infrastructure:
Marsh systems planted with vegetation designed to treat stormwater runoff.
Gently sloping strips of dense vegetation between paved areas that intercept and absorb stormwater.
Roofs covered with a system of contained vegetation, waterproofing, and drainage designed to reduce the amount of stormwater entering gutters.
Basins with capacity to store excess water during storms, then filter it back into the ground through plants and soils.
Mounds of compacted earth that can stop or redirect runoff and absorb stormwater.
Linear ditches or beds that collect runoff, often from roadsides or parking lots, and absorb it into highly porous soil.
Pavement that allows stormwater to soak through it and into the ground rather than flowing across the surface and into sewers.
Basins that capture stormwater before it reaches the ground, allowing it to be used later for things like watering lawns or washing cars.
Areas with native plants that absorb and filter stormwater but can also thrive in dry weather.
Vegetation planted along waterways that absorbs runoff and filters pollutants before they can enter the water.
Besides benefits like shade and aesthetics, trees absorb and filter stormwater.
Channels planted with trees, shrubs, or grasses that slow runoff and help absorb it into the ground; similar to rain gardens, but often larger and designed to manage runoff from a specific impermeable area like a parking lot.
Conserving land is an incredibly effective stormwater solution: Forests, wetlands, and other natural areas can filter and absorb massive amounts of stormwater, improving water quality and reducing flooding. Protecting a piece of open space from development reduces water pollution and flooding in the immediate area as well as downstream; conversely, paving over that land results in dirtier water and increased flood risk. For example, one study found that less than 5% of rain falling on forests runs off into waterways, compared to 95% for impermeable surfaces.
Land trusts and governments (local, state, and federal) may conserve land by acquiring and managing it or by acquiring conservation easements that limit use of the land to activities consistent with the easement’s conservation purposes.
Establishment of conservation-oriented land-use ordinances and—of equal importance—consistent enforcement of the ordinances and adherence to the good land-use principles underpinning the ordinances in making decisions about individual developments can also provide some land conservation benefits.
See ConservationTools.org for a wealth of land conservation resources, including:
Runoff from farms carries chemical fertilizers, pesticides, and livestock waste into waterways, killing wildlife and making waterways unsafe for fishing, paddling, and swimming. Implementing best management practices (BMPs) on farms can drastically reduce this runoff and pollution.
While the focus of agricultural BMPs is protecting water quality, some BMPs also help mitigate flooding by absorbing more stormwater into the soil, reducing the volume of runoff flowing into waterways. These BMPs are described below. For a more detailed overview, see the guide Turning Soils into Sponges.
Vegetated buffers that capture pollutants and reduce downstream flooding.
Fields planted in crops year-round filter pollutants, stabilize the soil, and absorb far more water than fields left fallow.
Leaving crop residue on the soil surface (rather than tilling it into the ground) preserves organic matter in the soil, reducing erosion and allowing the ground to absorb more stormwater.
Improving the efficiency of irrigation systems to reduce the amount of excess water running off fields and into waterways.
Sediment chokes biodiversity and clogs waterways, making floods more likely; stabilizing soil with vegetation or physical structures reduces the amount of sediment flowing into waterways.