using trees to reduce stormwater runoff
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Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
using trees to reduce stormwater runoff
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
stormwater runoff is the number one factor in the decline of
urban streams and
decreasing urban water
quality !
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
old news
The first models for predicting runoff appeared in the 1800s and used runoff coefficients to account for different land use and land covers.
•The Rational Method (Mulvaney 1851)
•Peak Discharge = Runoff Coefficient x Rainfall x Basin Area
•Runoff Coefficients:
•Forested ground is typically assigned a value of near 0.
•Pavement is given values approaching 100 percent
But why emphasize trees in particular versus other
stormwater practices?
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
save energy improve air quality provide habitat better quality of life neighborhood stability aesthetic values increase property value reduce noise good for business
trees are the original “multi-taskers”
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
??so if trees and forests provide so many benefits beyond reducing stormwater …shouldn’t they be more of a priority consideration
in site design.??
… yes, but only if trees are given credit for their work…and to give credit, we must be
able to provide numbers!
(How else can engineers calculate credits?)
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
don’t trees get some credit already?
not in most municipalities not enough to matter to most developers. not enough to equal their true value
Source: CWP
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
trees & stormwater: some conclusions
• Watershed health is linked to the amount of forest in the watershed and its distribution.
• Increases in tree cover and tree size will result in reduced total runoff and peak runoff rates (10% = 2-5%)
• Tree canopy has a greater effect on small storm events than on large storm events (2 year storm frequency)
• Effects on runoff are greatest when urban trees are large and well-established (site quality).
• Trees and stormwater management practices can coexist if planned and designed from the start.
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
Approaches to use trees for stormwater management
•Incorporate trees into stormwater practices•Pursue site opportunities for stormwater forestry•Make stormwater practices an amenity
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
incorporating trees into stormwater practices
•Traditionally not a celebrated union
•Some engineers don’t want trees in STPs
•Foresters want to know where are all the trees?
•Most of our practices end up losing trees due to poor maintenance
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
challenges…
Urban Foresters
Engineers/Planners
Now remember, you have to work
together Leftover disturbed areas are not the only place for trees
We can retain valuable trees that improve watershed functions
We can use trees in SW practices if we design it differently
We need wider streets and curbs
Keep the trees in the park, we need the tax revenue
Don’t worry, we’ll come back and plant trees later.
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
potential engineering conflicts
•Tree litter may clog pipes/outlets•Maintenance may be more difficult•Tree roots may puncture underdrains/filter fabric•Trees can reduce storage capacity•Limited maintenance access•Trees may compromise embankment stability
Source: Tim Schueler
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
conditions that limit tree growth in
stormwater/urban practices
• Compacted soils/limited soil volume
• High temperatures/drought• High winds• Physical damage from
mowers/browsers• Too much/too frequent
inundation• Urban pollutants (metals,
chloride)• Ice damage/scour
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
most stormwater projects are…
• built on the least valuable land
• constructed at the lowest cost
• designed only to manage quantity
• not intended for people
• UGLY!!!
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
Historic Approach to Stormwater Management: move water off the site as quickly as possible
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
typical stormwater pond with no trees
More recent approach is to temporarily detain runoff to control peak flows – this does not reduce
the volume of runoff or mimic pre-development hydrology
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
What opportunities are we missing?
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
Why integrate trees and stormwater?
• Potential benefits of trees in stormwater treatment practices: infiltration, pollutant removal, stabilization, habitat, reduced mowing costs, landscaping value
• Implementation of stormwater forestry practices has been limited - lack of collaboration among foresters and stormwater engineers
• Use of trees (non-structural practices) is more cost-effective than use of structural practices
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
Stormwater projects can reduce water quantity, improve water quality…and be beautiful.
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
Stormwater practices can be amenities for people…
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
• Good Stormwater Practices = Water Amenities
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
how do we get there?
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
stormwater forestry practice concept designs…what if?• Wooded wetland• Bioretention and bioinfiltration• Tree check dam• Alternating side slope plantings• Multi-zone filter strip• Forested filter strip• Linear stormwater tree pit• Stormwater dry pond
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
Third Generation The Forested Wetland—water quality + tree benefits
Wooded Wetland
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
Tree Clusters in Stormwater Ponds and Wetlands
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
Bioretention with trees
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
tree check dams
tree check dam section tree check dam axon
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
Alternating side slope plantings
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
Multi-zone filter strip
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
Forested filter strip
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
linear stormwater tree pits
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
stormwater drypond
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
stormwater drypond
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
Stormwater forestry opportunities in a watershed
• Schools• Parks• Highway rights-of-way • Vacant lots• Streams and shorelines• Utility corridors• Street medians and roadways• Parking lots• Home lawns (education and incentives are key)
Opportunities to build urban tree canopy that can enhance stormwater treatment
and improve watershed health
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
schools
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
parks
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
forest cover in parks limits runoff
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
highway right of way
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
vacant lots are a good opportunity for reforestation and
neighborhood beautification
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
Combining Reforestation and Soil Compost Amendments to Restore a Vacant Urban Lot
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
Reforesting stream buffers provides stream shading, bank stabilization, pollutant removal and other benefits
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
planting under utilities
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
Plant Trees During Development/Redevelopment
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
More shade means more time between repaving. 20% shade on a street improves pavement condition by 11%, which is a 60% savings for resurfacing over 30 years.
Planting along local roads
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
local roads median planting
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
Trees planted in a median strip
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
A typical cul-de-sac is a large expanse of pavement with no vegetation
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
Trees can be incorporated into cul-de-sac islands
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
No infiltration of rainfall& limited soil volume
Parking Lots
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
Trees in parking lots perimeter
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
What opportunities
are we missing?
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
So what’s with turf cover? fastest growing land cover in the US!
Sources: MTC (1996), VASS (1998) and PTC (1989)
(% of total turf cover)
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
the truth about turf
• Turf is fastest growing urban land cover in United States
• High compaction of urban soils produces more urban runoff, particularly at edges
• Lawns have highest nitrogen and phosphorous concentrations of any urban source area
See Urban Watershed Forestry Manual Part 1
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
Trees planted on home lawns provide shade and other benefits at maturity
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
Use trees to: block winter winds,
shade summer sun,
accent important views, and
screen private areas
Residential landscapes can be functional and beautiful
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
Stormwater Design Amenities, Emerging Discoveries
• Visible water trail that intrigues and Engages• Character of Water Design that responds to context• Information systems that educate• Design for Maintenance that shows intention• Physical Accessibility• Multiple Use • Public Support• Perceived Value • Municipal Support
Source: Echols, Pennypacker 06
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
12th street green street, portland oregon
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
Stormwater runoff from 8000 square feet flows downhill along the existing curb unit. Stormwater planter system reduces intensity of
a 25 year storm event by 70% or more.
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
Infiltration = 4 inches per hours
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
Seattle SEA Streets
Seattle SEA (Street Edge Alternatives) Streets Project uses graded swales to reduce impervious cover by 11% over
traditional streets. Project has decreased stormwater volume by 97 percent.
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
A concept drawing of the $800,000 street edge alternative (SEA) project shows 14-foot-wide curved street, swales, additional trees, vegetation and diagonal
parking areas for cars.
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
SEA Streets
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
The Cascade Prototype project at N. 110th St. after most of the construction has been completed and
before planting.
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
• Stephen Epler Hall, Portland State
Visible water trail that intrigues and Engages
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
Growing Vine, Seattle Washington
“beckoning cistern” by buster simpson
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
alternative sidewalk design
Traditional sidewalk designs utilize individual tree pits (left) which confine roots; alternative designs cluster trees (right), which allows them to share rooting space. This reduces the
need for tree roots to grow under pavement.
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
alternative sidewalk materials
• Reinforced or thicker concrete slabs
• Pervious concrete
• Decomposed granite and compacted gravel
• Permeable pavers
• Recycled rubber
• Other ideas? *Goal is to allow tree roots to grow under sidewalks without causing damage
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
so what if we…
create watershed projects that target areas and actions needed to protect, expand, reforest and integrate tree cover with other development, stormwater, and landscaping activities?
create plans that facilitate goal setting and allows tracking of progress?
Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry
• What opportunities can you identify to integrate urban forestry, watershed forestry, engineering and design?
• What if….?