Rain Gardens

Rain gardens are shallow, landscaped depressions that capture stormwater runoff from rooftops, sidewalks and streets. The runoff is filtered and allowed to infiltrate into the ground over a period of 24–48 hours. During this time, much of the pollutants found in the stormwater can be removed by physical, chemical and biological methods. Rain gardens:

  • filter (physical)
  • settle out pollutants (physical)
  • remove nutrients through plant uptake (biological/chemical). Nutrients can lead to excess plant growth in lakes and streams
  • remove some heavy metals as they are taken up by specific plants (biological/chemical)
  • allow UV radiation to reach and have opportunity to kill bacteria (physical/biological)
  • provide surface for pollutants to attach to soil and then be removed from the catch basin to stream cycle (chemical/physical)

The stormwater filters into the soil within 24–48 hours; specifically so that there is not sufficient time for mosquitoes to breed. This infiltration of stormwater does provide input to the groundwater. This also reduces the water entering the catch basin which travels to the nearest stream or waterbody, often causing flooding even during small rain events.

Want More Information on Rain Gardens?

Download the free Rain Garden Manual of New Jersey.

Rain Garden Rebate Program for Hillsborough Residents

Hillsborough residents can get a rebate of up to $450 for installing a rain garden (423k PDF).

Hillsborough Township Rain Garden

This rain garden was designed by Tobiah (Toby) Horton, assistant professor in the Rutgers Department of Landscape Architecture, and New Jersey Agricultural Experiment Station (NJAES) extension specialist in landscape architecture.

Photo: Locust trees at rain garden.
Honey locust trees were placed within the expanse of impervious paving by Hillsborough Township's entrance, contributed by Hillsborough Township. The trees help disconnect the impervious surfaces and were included as part of the overall concept plant for the Municipal site designed by the Rutgers Cooperative Extension Landscape Architect.
Photo: Rain garen overflow.
The rain garden by the overflow. The overflow pictured here will allow excess water to enter the storm drain system when the rain garden exceeds 6 inches of holding capacity.
Photo: Long view of the rain garden.
Long view of the rain garden. Hillsborough Township is providing irrigation for the first year to assure success of the newly planted perennials, shrubs, and trees. The path to the right of the picture is pervious and provides a walking/running opportunity allowing residents and employees to personally experience their rain garden.
Photo: Rain garden and sidewalk.
Water is led off the sidewalk to the rain garden. The water is both directed and filtered by the rocks as it enters the rain garden.
Photo: Hillsborough Township Municipal building entrance.
The entrance to Hillsborough Township Municipal building and Library previously was a large expanse of impervious brick. Previously there was approximately 7,800 square foot of impervious surface, including the adjacent sidewalk, and the majority drained directly to the storm sewer system.
Photo: Rain garden planted.
Planting Day at Hillsborough Township. Along with NJ Tree Foundation staff and Rutgers Water Resources Program staff, Hillsborough Township employees volunteered to assist with planting joined by volunteers from Rutgers Master Gardeners of Somerset County.
Photo: Rain garden entrance path.
The entrance path leading into the rain garden. The walking/running path provides residents and municipal employees with the ability to experience the rain garden as part of their overall experience.

Cooperative Extension of Somerset County