Green Infrastructure comes in many forms, all of which infiltrate, evaporate or recycle storm water runoff. Some are complex and expensive, while others are simple and economical. Nevertheless, all do the important job of conserving our precious resource, water.
Why use Green Infrastructure?
Green infrastructure helps protect and restore naturally functioning ecosystems and provides a framework for future development. It provides a diverse range of ecological, social, and economic functions, including: enriched habitat and biodiversity, maintenance of natural landscape processes, cleaner air and water, increased recreational and transportation opportunities, improved health, and better connection to nature and sense of place.
Well-planned green space has also been shown to increase property values and decrease the costs of public infrastructure and public services, including the cost of storm water management and water treatment systems. To learn more about the benefits of green infrastructure and ways you can implement it in your community, please check out Riverkeeper’s “Know Your Sewershed” guide, available for download here.
Types of Green Infrastructure:
Green Roof: a roof of a building that is partially or completely covered with vegetation and soil, or a growing medium, planted over a waterproofing membrane. It may also include additional layers such as a root barrier and drainage and irrigation systems. Also known as “living roofs,” green roofs serve several purposes for a building, such as absorbing rainwater, providing insulation, creating a habitat for wildlife, lowering overall urban air temperatures, and combatting the heat island effect. There are two types of green roofs: intensive roofs, which are thicker and can support a wider variety of plants but are heavier and require more maintenance, and extensive roofs, which involve a light layer of vegetation and require less maintenance than an intensive green roof.
Rain Garden: a planted depression that allows rainwater runoff from impervious urban areas like roofs, driveways, walkways, and compacted lawn areas to be absorbed. This reduces rain runoff by allowing storm water to soak into the ground (as opposed to flowing into storm drains and surface waters which causes erosion, water pollution, flooding, and diminished groundwater). Rain gardens can cut down on the amount of pollution reaching creeks and streams by up to 30%. Native plants are recommended for rain gardens because they generally don’t require fertilizer and are more tolerant of one’s local climate, soil, and water conditions. The plants — a selection of wetland edge vegetation such as wildflowers, sedges, rushes, ferns, shrubs and small trees — take up excess water flowing into the rain garden. Water filters through soil layers before entering the groundwater system. Root systems enhance infiltration, moisture redistribution, and diverse microbial populations involved in filtration. Through the process of transpiration, rain garden plants return water vapor into the atmosphere.
Bio-retention: the process by which contaminants and sedimentation are removed from storm water runoff. Storm water is collected into the treatment area which consists of a grass buffer strip, sand bed, pooling area, organic layer or mulch layer, planting soil, and plants. Runoff passes first over or through a sand bed, which slows the runoff’s velocity, distributes it evenly along the length of the pooling area, which consists of a surface organic layer and/or ground cover and the underlying planting soil. The pooling area is graded, its center depressed. Water is pooled to a depth of 6 inches and gradually infiltrates the bio-retention area or is evapotranspired. The bio-retention area is graded to divert excess runoff away from itself. Stored water in the bio-retention area infiltrates over a period of days into the underlying soils.
Rain Barrel: a container that collects and stores rain water for future uses, such as watering landscaping, and for decreasing the amount of storm water runoff that leaves your property. A rain barrel is typically inserted under the downspout from a roof to channel rainwater into the barrel for later use. This is a technology that has been used for thousands of years! This reduces the demand on our drinking water source and conserves precious fresh water. Rain barrels also help address an important water pollution issue caused by overflowing sewers during heavy rain. Rain barrels are available for order here.
Permeable Pavement: a range of materials and techniques for paving roads, parking lots, and walkways that allows the movement of water and air around the paving material. Although some porous paving materials appear nearly indistinguishable from nonporous materials, their environmental effects are fundamentally different. Whether the material used is pervious concrete, porous asphalt, paving stones or bricks, all these pervious materials allow precipitation to percolate through areas that would traditionally be impervious and instead infiltrates the storm water through to the soil below.
Downspout Disconnection: Disconnecting downspouts from the sewer system allows roof water to drain to lawns and gardens. It’s a more natural way to manage roof runoff because it allows water to soak into the ground as plants and soils filter pollutants.Downspouts on many homes are connected directly the combined sewer system and roof runoff from those homes contributes to combined sewer overflows (CSOs). Disconnecting those downspouts reduces the amount of water entering the system and reduces CSOs. Downspouts must be disconnected safely to protect people and property.
Swale: a low tract of land, especially one that is moist or marshy. The term can refer to a natural landscape feature or a human-created one. Artificial swales are often designed to manage water runoff, filter pollutants, and increase rainwater infiltration. Swales are designed to slow and capture runoff by spreading it horizontally across the landscape (along an elevation contour line), facilitating runoff infiltration into the soil. This type of swale is created by digging a ditch on contour and piling the dirt on the downhill side of the ditch to create a berm. In arid climates, vegetation (existing or planted) along the swale can benefit from the concentration of runoff.
Green Space: Green space is an area within an urban environment which is dedicated to nature. One of the most familiar forms of green space is a recreational park, such as New York City’s famous Central Park, although green space can also take the form of urban wetlands or urban forest canopy.
Wetland Restoration: Wetland restoration is an essential tool in the campaign to protect, improve, and increase wetlands. Wetlands that have been filled and drained retain their characteristic soil and hydrology, allowing their natural functions to be reclaimed. Restoration is a complex process that requires planning, implementation, monitoring, and management. It involves renewing natural and historical wetlands that have been lost or degraded and reclaiming their functions and values as vital ecosystems. Restoring our lost and degraded wetlands to their natural state is essential to ensure the health of America’s watershed.