What is Green Stormwater Infrastructure?

An illustration of the ways runoff and pollutants flow directly into local creeks via storm drains.
Left: Landscaped areas and pervious surfaces capture runoff, reducing the quantity of pollutants flowing into local creeks. Right: Runoff and pollutants flow directly into local creeks via storm drains

In natural landscapes, rain that falls on the ground mostly soaks, or infiltrates, into the soil. However, in urban areas, impervious surfaces such as roofs, pavement, and streets, prevent infiltration. This results in an increase in stormwater runoff and pollutants flowing into storm drains, local creeks, and the Bay.

Cities and towns in Santa Clara Valley are working together to create sustainable or green streets, buildings, and parking lots that mimic natural landscapes by incorporating green stormwater infrastructure features. These features allow rainwater runoff to soak into the ground and be filtered by soil. This reduces the quantity of water and pollutants flowing into storm drains and local creeks.

Green stormwater infrastructure features include the following:

  • Dispersion of Stormwater Runoff into Landscaping
  • Bioretention Areas or Rain Gardens
  • Rainwater Harvesting and Use
  • Green Roofs
  • Pervious Concrete, Porous Asphalt, and Pervious Pavers
  • Infiltration Trench

Map of Stormwater Treatment Measures in Santa Clara Valley - link to interactive data portal

Access the Stormwater Treatment Measure Data Portal (opens in new window) to reach the interactive data portal on Stormwater Treatment Measures (STMs) constructed to-date in the Santa Clara Valley. The data portal includes Low Impact Development (LID) and Green Stormwater Infrastructure (GSI) projects constructed on private properties and public projects constructed in the public right-of-way.

Photograph showing example of landscaped surface to help with stormwater drainage. Dispersion of Stormwater Runoff into Landscaping
Landscaped areas can be designed to collect stormwater runoff from building roofs and paved areas. Stormwater infiltrates into these areas, and pollutants are filtered out or broken down by the soil and plants.
Photograph of an example of a Rain Garden which is a landscaped area in the middle of a sidewalk. Bioretention Areas or Rain Gardens
These landscaped areas collect, treat, and infiltrate runoff using plants and a specified soil mix. Biotreatment areas can be incorporated into parking lots, curb extensions, park strips, traffic circles, and street edges and medians. Planter boxes next to buildings, tree wells, and tree trenches can also be designed as biotreatment areas.
Photograph of a rainwater storage tank. Rainwater Harvesting and Use
Rainwater harvesting systems collect and store rainwater for later use. They slow and reduce stormwater runoff, and that stored water can be used for landscape irrigation or toilet flushing.
Photograph of a landscaped roof which is an example of a green roof. Green Roofs
Building roofs covered in soil and vegetation enable rain water infiltration, storage, and evapotranspiration (water loss from soil and plants to the surrounding air). In addition to stormwater benefits, Green roofs can also mitigate urban heat island effects while improving air quality and building energy efficiency.
Photograph of grid pavers with gaps filled with gravel. Pervious Concrete, Porous Asphalt, and Pervious Pavers
Pervious surfaces let rain percolate through them and into the soil. They are generally used in crosswalks, sidewalks, plazas, driveways, parking spaces, street edges, and emergency vehicle access lanes. Pervious surfaces include the following:

  • Pervious concrete or porous asphalt
  • Grid pavers with gaps filled with gravel or turf
  • Interlocking pavers made of pervious material
  • Solid interlocking pavers that have gaps between
A photograph of a street that contains an infiltration trench. Infiltration Trenches
Infiltration trenches are excavated trenches backfilled with gravel. They capture, store and infiltrate stormwater runoff into the soil. They can be used along street edges and in alleys and parking lots.