Green Roofs and Green Infrastructure

High-Performance Building WeekJune 16, 2010

Environmental Benefits of Green Roofs, Green Infrastructure, and Low-Impact Development:• Control stormwater runoff• Improve water quality• Conserve water• Reduce urban heat island effect• Store carbon• Improve air quality• Reduce building energy use• Create biohabitat

Impervious Surface and Water Quality

• Natural landscapes clean and filter water, slow and reduce runoff

• Traditional development increases impervious surfaces

• In the U.S., impervious surfaces are increasing 3% annually

• Result: Urban and suburban stormwater runoff is the #1 cause of pollution in urban watersheds

Sources: Urban Green Space: Effects on Water and Climate, Regina E. Bonsignore, University of Minnesota, 2003; Stream Corridor Restoration: Principles, Processes, and Practices, Federal Interagency Stream Restoration Working Group, 1998.

Impervious Surface and Water Quality

• Water quality begins to degrade when impervious cover exceeds 10%

• Water quality becomes “poor” when impervious cover exceeds 25%

• D.C. – 46 % impervious• NYC – over 90% impervious• Stormwater concerns:

– Pollutant load – Water temperature– Speed and quantity causes

erosion and streambed scouring

Sources: Urban Green Space: Effects on Water and Climate, Regina E. Bonsignore, University of Minnesota, 2003; Stream Corridor Restoration: Principles, Processes, and Practices, Federal Interagency Stream Restoration Working Group, 1998.

Water Quality: Combined Sewer Outflows

• Heavy storms = release of untreated sewage and runoff into watersheds.

• Nationwide, CSOs affect 772 cities, 40 million people

• Scope of problem in D.C. — 2.5 billion gallons of untreated wastewater and precipitation released annually

• In some parts of D.C., one-tenth inch of rain triggers CSOs

• Cost of fixing problem in D.C. -- $2.6 billion

Sources: U.S. Environmental Protection Agency; D.C. Water and Sewer Authority

Water Quality: Combined Sewer Outflows

• CSOs are #1 cause of beach closures around urban areas

Impervious Surface and Flooding

• As development increases, so does the amount and speed of stream flow

• As stream flow speeds increase, so does flooding

Source: U.S. Geological Survey

Houston 2001: Tropical Storm Allison

• $6.5 billion (‘08 USD) in damages• 41 deaths• 70,000 homes flooded

Traditional Development = Urban Heat Island

• = Increased air pollution and related health problems

• = Increased carbon footprint -- higher temperatures require more energy for cooling

Sources: U.S. Environmental Protection Agency; Paul R. Baumann, Department of Geography, SUNY Oneonta

Test

April 15, 2004

Image Courtesy of Michael Van Valkenburgh Associates, Inc. & ASLA

Roofs are 15-25% of surface area in cities

ASLA: Pre-Green Roof

ASLA Green Roof

ASLA Green Roof Results

• Retains 100 % of a one-inch rainfall and over 77 % of total annual rainfall

• Reduces the amount of nitrogen entering the watershed

• Building energy use reduced by 10 % in winter months

• Temperature as much as 43.5 cooler in the summer

•25% reduction in stormwater leaving site

•Bioretention planters filter and clean water

• LEED platinum • Integrated stormwater and

wastewater system

Sidwell Friends School, D.C.Image courtesy of Andropogon

• Biofilters treat building wastewater for reuse

• Uses constructed wetlands, rain gardens, bioswales, biofiltration and habitat pools

Sustainable Housing Community: High PointSustainable Housing Community: High PointSeattle, WashingtonSeattle, WashingtonPhoto courtesy of Mithun

• 120 acre residential redevelopment

• Returns clean water to an urban salmon-bearing stream

Photo courtesy of Mithun

• Rain gardens, pervious pavements, 22,000 linear feet of bioswales

• Native plants and rich vegetation

• Controls water flow for 100-year storm events

Photo courtesy of Mithun

• Incorporates “Complete Streets”

• Handles 100-year storm rainfalls

SW 12th Avenue, Portland, ORSW 12th Avenue, Portland, ORPhoto courtesy of Kevin Robert Perry, ASLA Photo courtesy of Kevin Robert Perry, ASLA

• Retail district “green street” • Retains 100% of rainfall from

a 100-year storm• Channels water from street

into stormwater planters

NE Siskiyou, Portland, ORNE Siskiyou, Portland, ORPhoto courtesy of Kevin Robert Perry, ASLA Photo courtesy of Kevin Robert Perry, ASLA

•Residential “green street”

Photo courtesy of Kevin Robert Perry, ASLAPhoto courtesy of Kevin Robert Perry, ASLA

Photo courtesy of Kevin Robert Perry, ASLAPhoto courtesy of Kevin Robert Perry, ASLA

Buffalo Bayou Promenade, Houston, TXPhoto courtesy SWA Group

•Turned derelict riverfront into 23 acres of park land•Mitigated erosion•Enhanced flood control

Buffalo Bayou Promenade, Houston, TXPhoto courtesy SWA Group

• Reduces air temperature• Provides recreation

opportunities• Creates biohabitat

Important Legislation• HR 4202 The Green Infrastructure for

Clean Water Act of 2009– Provides grants to states, localities, and other

qualified entities for plan, design and implementation of green infrastructure projects that would mitigate stormwater runoff and address other water quality and quantity issues

HR 4202 – Recommends changes to local ordinances,

permitting processes, and zoning regulation to encourage the use of Green Infrastructure solutions

– Establishes a Green Infrastructure program at EPA to promote the use of green infrastructure

– Creates up to 5 Green Infrastructure centers of excellence to conduct research and develop best management practices

Questions?Roxanne Blackwell rblackwell@asla.org 202.216.2334

Kevin O’Harakohara@asla.org202.216.2370