Natural Resource Defense Council: Rooftops to Rivers II

From the Natural Resource Defense Council (NRDC), Rooftops to Rivers II describes the challenges of managing stormwater, and the benefits and economics of employing green infrastructure to do so. The report explains how population growth, changing landscapes, aging infrastructure, and climate change are placing increasing pressures on stormwater management. Highly detailed case studies are developed for 14 cities that are all leaders in employing green infrastructure solutions to address stormwater challenges. Local, state and national level policy recommendations are offered also.

The stormwater management impacts addressed are related to development patterns, the resulting loss of pervious surfaces, deficiencies in stormwater infrastructure and regulatory structures, and impacts from both climate change and increasing population trends. According to the report, climate change will exacerbate the problems caused by aging and failing infrastructure and current development patterns through higher temperatures; shifts in the time, location, duration, and intensity of precipitation events; increases in the number of severe storms; and rising sea levels are expected to shrink water supplies, increase water pollution levels, increase flood events, and cause additional stress to wastewater and drinking water infrastructure.

Green infrastructure helps stop runoff pollution by capturing rainwater and either storing it for use or letting it filter back into the ground, replenishing vegetation and groundwater supplies. Examples of green infrastructure include green roofs, street trees, increased green space, rain barrels, rain gardens, and permeable pavement. 

The economics of green infrastructure are explained, including how it can be less expensive than some conventional infrastructure investments and mitigate the costs of energy use and flooding. The report also details traditional and innovative financing mechanisms, including incentivizing green infrastructure through codes and zoning changes, and government-run financing and inducements such as streamlined permitting and inspection processes, cash rebates, and tax credits. 

Innovative financing approaches for financing stormwater retrofits are discussed, which depend upon a municipality having in place a stormwater billing structure that includes a credit for owners who install stormwater retrofits. Four financing approaches that rely on such a fee structure are summarized: Property Assessed Clean Energy (PACE), on-bill financing, off-balance-sheet project financing, and credit enhancement to accelerate private investment in retrofits.

14 Case Studies chronicle how green infrastructure is helping manage urban stormwater:

  • Aurora, Illinois
  • Chicago, Illinois
  • Kansas City, Missouri 
  • Milwaukee, Wisconsin 
  • Nashville, Tennessee
  • New York, New York 
  • Philadelphia, Pennsylvania 
  • Pittsburgh, Pennsylvania 
  • Portland, Oregon
  • Rouge River Watershed, Michigan 
  • Seattle, Washington
  • Syracuse, New York
  • Toronto, Ontario Canada
  • Washington, D.C.


NRDC’s “Emerald City” metric identifies six actions cities should undertake to fully realize their green infrastructure investment. Each action is identified along with specific policy recommendations for local leaders. Only one of the cities profiled in this report, Philadelphia, met all six criteria:

  1. Develop a long-term green infrastructure plan
  2. Develop and enforce a strong retention standard for stormwater
  3. Require the use of green infrastructure to reduce, or otherwise manage runoff from, some portion of the existing impervious surfaces
  4. Provide incentives for residential and commercial private party use of green infrastructure
  5. Provide guidance or other affirmative assistance to accomplish green infrastructure
  6. Ensure dedicated funding source for green infrastructure (Ten of the cities profiled - Aurora, Kansas City, Milwaukee, Nashville, New York, Philadelphia, Portland, Seattle, Syracuse and Washington, D.C. - have a dedicated funding source for green infrastructure.)




Publication Date: 2011

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  • Best practice
  • Case study


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