What is Green Stormwater Infrastructure?


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:

Local municipalities are developing Green Stormwater Infrastructure (GSI) Plans to incorporate green stormwater infrastructure features into new and existing drainage infrastructure on public properties and rights-of-way, including streets, storm drains, and parking lots. SCVURPPP is developing a guidance document (“Green Stormwater Infrastructure Handbook”) to provide guidance to municipal staff on how to incorporate green stormwater infrastructure features into public street, parking lot and park retrofit projects. The GSI Handbook will be available in Spring 2019.

Click here for a map of example local projects that have integrated green stormwater infrastructure features. For more information on how green stormwater infrastructure features help our communities, please visit the Green Streets webpage on the Watershed Watch website.

See below for spotlight fact sheets on local and regional Green Street projects

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.
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.
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.
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.
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
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.

Green Stormwater Infrastructure Documents

DateTitleCategoriesTags
11/29/2018Workshop Materials – Stormwater Resource and Green Stormwater Infrastructure Planning: Opportunities for Multi-Benefit Projects in Santa Clara Valley – 11/29/18Workshops,
8/29/2018GSI Handbook Workshop #2 – April 24, 2018Workshops,
8/29/2018GSI Handbook Workshop #1 – April 10, 2018Workshops,
4/19/2017Green Infrastructure Design and Implementation Workshop – April 19, 2017Workshops,