Stormwater | Reforesttacoma

Stormwater:

Why Integrate Stormwater and Urban Forest Management?

Integrating Stormwater Services with Urban Forestry:
- Stormwater management is more closely related to urban forestry than wastewater systems because trees and urban forests play a crucial role in managing stormwater runoff by intercepting rainfall, promoting infiltration, and reducing erosion, while wastewater systems focus on collecting and treating sewage. Municipalities Integrate Stormwater Services and Urban Forestry to leverage the natural benefits of trees for managing stormwater runoff, improving water quality, and enhancing the overall urban environment, leading to cost savings and a more sustainable city.
Why is this important to Tacoma?
- A quick look at these two charts will tell you why. From the Puget Sound Urban Tree Canopy and Stormwater Management project in which Tacoma took part, including Sarah Low and Mike Carey, we can see how significant Tacoma’s impervious surface really is, and how it will continue to get worse as we add more roofs, streets, hardscape, sidewalks, parking, patios, etc.

After seeing so many maps depicting our diminishing tree canopy, to see this one clearly demonstrates how closely related our urban forest is to stormwater runoff.

Why Trees Make a Difference:

A couple of minutes with this chart from the Puget Sound Urban Tree Canopy and Stormwater Management Handbook will clarify why trees can make such a difference. Some crazy terms, but good descriptions.ons!

Integrating Green with Gray:

The integration of the two systems requires joint planning, common funding, and integrated resources.

Stormwater and Trees

Why Integrate Stormwater Services With Urban Forestry?

Stormwater Management:

Stormwater management focuses on managing the runoff of rainwater and snowmelt, which can pick up pollutants and flow into storm drains and waterways.
Urban forests and trees are effective at mitigating stormwater runoff through various mechanisms.
Tree canopies intercept rainfall, reducing the volume and intensity of runoff.
Tree roots help to increase soil infiltration, allowing stormwater to soak in the ground instead of flowing over the surface.
Urban forests also help to prevent erosion and improve water quality.

Wastewater Systems:

Wastewater systems are designed to collect and treat sewage and other wastewater from homes and businesses.
They are not directly involved in managing stormwater runoff, which is a separate issue.
Wastewater systems may occasionally discharge excess untreated sewage directly to nearby streams, rivers or other water bodies during heavy rainfall or snowmelt.

Relationship Between Urban Forestry and Stormwater Management:

Urban forestry practices, such as planting trees and maintaining urban forests, can significantly contribute to effective stormwater management. (Urban Forest Stormwater Infrastructure)
Urban forests can help to reduce the volume and impact of stormwater runoff, improving water quality and reducing the strain on traditional stormwater management infrastructure.
Integrating urban forestry into stormwater management plans can lead to more sustainable and cost-effective solutions. (Integrating Stormwater Services with Urban Forestry)

Tacoma’s Leading-Edge Example:

The City of Tacoma and Metro Parks Tacoma shared a vision to provide stormwater treatment through a park amenity at the entrance to Point Defiance Park.
Functionally, this facility is designed to capture the worst pollutants before they wash into an impaired area of Puget Sound overloaded with heavy metals from the Tacoma Asarco Smelter Plume, a toxic legacy from a copper smelter that operated for nearly 100 years. This innovative approach provides treatment for 754 acres in a footprint of only 5,500 square feet. This is a major step forward in improving water quality that can be replicated around the region.

Pt. Defiance Regional Treatment Retrofit Rendering.

This is not gray infrastructure. This is the application of green infrastructure as was its original purpose. It can be applied is smaller and strategic places all over the City.

Examples of Stormwater Urban Forestry Integration

Narrowing Streets: Cities across the U.S. and Canada have reevaluated their street design standards and adopted narrower street standards. In Portland, OR, the city created a Skinny Street program, which has reduced minimum residential street widths by as much as 12 feet to 20 to 26 feet depending on parking needs.6 Tacoma has existing residential roadways that range from 24 to 36 feet, with the majority of streets falling between 28 and 32 feet. Twenty-eight feet is the standard the City of Tacoma uses for new residential streets. Narrowing a roadway from 32 feet to 28 feet reduces the amount of impervious surface by about 12.5%, or about 1,200 sq. ft on a 300 ft-long block.
- Southworth, M. “Walkable Suburbs? An Evaluation of Neotraditional Communities at the Urban Edge.” Journal of the American Planning Association 63, no.1 (1997):28-44.

Rain Garden in Planting Strip Area:

Rain gardens are bioretention facilities consisting of planted depressions with a layer of specialized soil mix that are designed to allow stormwater runoff from streets, sidewalks, driveways, yards, and roofs to infiltrate through the specially designed soil mix to provide water quality treatment. In locations where infiltration is possible, rain gardens may also provide onsite retention of stormwater. Rain gardens are designed to maximize soil-water contact and to treat runoff by filtering out sediments using vegetation and a soil mix. Rain gardens may function as treatment alone or as treatment and retention facilities.