What is Green Stormwater Infrastructure?
Photo Location: Rain Garden at 12th and Reed
Photo Credit: Meliora Design
Green Stormwater Infrastructure (GSI) is a nature-based solution to water quality issues that urban stormwater runoff causes and provides greater benefits than conventional (or “Gray”) stormwater solutions. GSI combines economic and environmental sustainability, adaptability, resiliency, and social equity. GSI is defined as soil-water-plant systems that intercept stormwater, infiltrate a portion of it into the ground, evaporate a portion of it into the air, and in some cases release a portion of it slowly back into the sewer system. In addition to better stormwater management practices and improved water quality, GSI provides benefits such as beautified communities, improved public health, creation of ecological habitat, and enhanced local economic vitality.
Rain Garden:
A rain garden is planted lower than the surrounding area to collect stormwater before it drains directly into the sewer. Plant species are selected based on their ability to thrive in varying weather conditions, whether extremely wet or very dry. Rain gardens filter pollutants, replenish groundwater, and provide habitat for birds and insects.
Photo Location: Rain Garden at Nebinger School;
Photo Credit: Philadelphia Water Department
Stormwater Planter:
Stormwater planters are set into the sidewalk and filled with vegetation, soil, and stone. Stormwater is stored in the bottom of the planter so that the plants can use the water as they need it. A stormwater inlet collects water from the street and directs it into the planter. The planter also has small openings to catch stormwater running down the sidewalk. Not only do plants use rainwater as a source of hydration, but they also slow the passage of water into the soil and filter pollutants from it.
Photo Location: Stormwater Planter at Columbus Square;
Photo Credit: Philadelphia Water Department
Stormwater Tree Trench:
These trees are connected by a trench beneath the sidewalk that stores stormwater while providing water for the trees. Water flows down the street and enters the trench through the stormwater inlet, where a perforated pipe distributes runoff throughout the trench. A storage trench beneath the ground holds the water. Water is absorbed into the earth or flows slowly into the sewer. A tree’s root system uses the rainwater to help it grow.
Photo Location: Tree Trenches in South Philadelphia;
Photo Credit: Philadelphia Water Department
Green Roof:
A green roof is a roof or section of roof that is vegetated. A green roof system is composed of multiple layers including waterproofing, a drainage layer, an engineered planting media, and specially selected plants. A green roof can be installed on many types of roofs, from small slanting roofs to large commercial flat roofs. A green roof is effective in reducing the volume and velocity of stormwater runoff from roofs by temporarily storing stormwater, slowing excess stormwater released into the combined sewer system, and promoting evapotranspiration.
Photo Location: Green Roof at the Free Library of Philadelphia, Central Branch;
Photo Credit: Philadelphia Water Department
Stormwater Bumpout:
A stormwater bumpout is a landscaped extension of the curb. Stormwater runs down the street and into the bumpout, where it infiltrates the soil and waters the plants.
Bumpouts are planted with grasses, perennials, and shrubs. These plants soak up water that collects in the bumpout. They are selected for their ability to thrive in extremely wet or dry weather. Plants, soil, and stone filter and remove pollutants from the stormwater as it soaks into the ground.
Photo Location: Stormwater Bumpout at Shepard Recreation Center;
Photo Credit: Philadelphia Water Department
Swale:
A swale is a lower tract of land that collects stormwater runoff. Stormwater from the street or from uphill flows downhill and from the surrounding area into the swale. Plants filter water and enhance streetscapes. Water filters through the soil.
Photo Location: Swale and Rain Garden in South West Philadelphia;
Photo Credit: Philadelphia Water Department
Infiltration Trench (roads/basketball court):
During heavy storms, stormwater overwhelms the sewer system, sending pollutants into creeks and rivers. An infiltration trench is a below-ground bed of stone that collects and redirects this excess stormwater. Inlets catch water from the street and directs it into the trench, which is located under the pavement/basketball court. The water passes through the gaps between the stone and seeps to the bottom of the trench. The water is absorbed into the earth or flows slowly back into the sewer after the storm has passed.
Photo Location: Infiltration Trench at Clark Park Basketball Court;
Photo Credit: Meliora Design
Porous Paving (asphalt/porous play surface):
Rainwater can’t soak into traditional pavement. Instead, water flows into sewers and carries pollutants from the street into our waterways. Special materials, such as porous asphalt/porous play surfaces, allow water to pass through their surfaces into the stone and ground below. These materials slow, redirect, and filter water through the soil instead of overwhelming the sewers.
Photo Location: Porous Pavement at Heron Basketball Court;
Photo Credit: Philadelphia Water Department
Stormwater Wetlands:
Stormwater wetlands seek to imitate the functions of natural wetlands, therefore becoming aesthetic assets to the community and providing habitats for wildlife. Stormwater is piped into the wetland or flows downhill into the wetland from the surrounding area. Water is collected and stored in a pool that allows water to filter through the soil. Excess stormwater drains to the sewer.
Photo Location: Saylor Grove Stormwater Wetland;
Photo Credit: Philadelphia Water Department