Green Infrastructure

What is Green Infrastructure?

Briarcliff rain garden. Part of Green Infrastructure project in Millers Creekshed

Briarcliff rain garden. Part of Green Infrastructure project in Millers Creekshed

Infrastructure is the foundation of modern living. It consists of roads, bridges, buildings, pipes, cables, parking lots and more, providing important resources such as communication, transportation, economic development, safety, and artistic expression.

Yet there is a side to infrastructure that has often been overlooked in human development: green infrastructure (GI). If railroads and buildings can be called gray infrastructure, then open spaces, wetlands, streams and rivers are green infrastructure. The ecosystem services they provide have always undergirded our towns and cities, but only recently have we come to appreciate and quantify their value. Through GI, our water is cleaned, our natural settings are preserved, local wildlife find habitat, and our temperatures are moderated . . . all free of charge.

Naturally-occurring GI, such as wetlands and meandering streams, can be mimicked through human-constructed GI for the purpose of managing stormwater. Designers and engineers now construct bioswales, rain gardens, green roofs, pervious pavement, and various site-specific infiltration designs. The point of these projects is to draw stormwater into the groundwater instead of piping it quickly into streams, where it carries pollution raises the water temperature and causes flashy, eroding creeks. Vegetated GI features capture rain water, filter it through the soil, cool it, and slowly deliver it to streams via groundwater.

Green infrastructure is not merely rain gardens and bioswales. Each of these features would be more accurately described as Low Impact Development (LID), or the implementation of best management practices at the site-specific level. GI, like grey infrastructure, expands the same idea to a community-wide scope. Its focus is on the planned, strategic placement of LID features and on the accounting of reduced stormwater volume and pollutant loads those features provide. It requires planning and inter-jurisdictional communication. (Read more about the differences between LID and GI along with case studies).

Gray infrastructure and GI are similar in some ways, but differ in others:

 Gray infrastructure . . .

  • Removes stormwater and delivers it  to local streams quickly
  • Overlays or replaces natural systems with impervious structures
  • Requires planning and costly maintenance
  • Requires upgrading to accomodate increased stormwater flow that results from development and climate change
  • Is limited to stormwater-removal benefits such as flood reduction

 Green Infrastructure . . .

  • Treats stormwater on-site and delivers it to streams slowly
  • Incorporates natural systems
  • Requires planning and less-costly maintenance
  • Can supplement grey infrastructure to prevent major system upgrades
  • Has multiple, quantifiable benefits beyond stormwater-removal

Green Infrastructure Projects

HRWC, working with partner organizations in Washtenaw County, developed an inventory and map of Green Infrastructure projects for the county. The map shows individual GI projects by type including bioretention, pervious paving, green roofs, native restoration and residential rain gardens. Each project location on the map includes a link to a project fact sheet complete with contact information for the project owner. If you find errors in project information or would like to submit a new project for inclusion on the map, please e-mail Ric Lawson.

Green Infrastructure and Sustainability

A community that incorporates GI alongside gray infrastructure for stormwater management is concerned about sustainability. The economic benefits of GI have been shown to outweigh those of grey infrastructure, especially at the community-wide scale (see, e.g., EPA’s 2007 “Reducing Stormwater Costs through Low Impact Development (LID) Strategies and Practices,” American River’s 2012 “Banking on Green” and “Economic Benefits of GI: Great Lakes Region,” CNT’s “Value of GI,” and numerous others). In addition, GI helps protect water quality and aquatic ecosystems. It retains a natural landscape aesthetic, which increases property values and quality of life. It provides habitat for local and migrating birds and wildlife. GI is a smart choice for stormwater management because of its many benefits.

Yet many barriers stand in the way of GI implementation. That is why HRWC has spent a year learning about and describing the barriers. We interviewed county, city, and township managers, surveyed the latest literature, and brainstormed options for overcoming the barriers. As we approached the end of our study, we hosted a series of “Growing Green Infrastructure Forums” with our local partners. Check out the results.

 What else can I do about my stormwater?

You can install your own rain garden with the help of designers at the Washtenaw County Resource Commissioner’s office.

You can disconnect your downspouts and use your lawn or garden to cleanse and cool your stormwater.

You can invest in a rain barrel at the end of your downspout to collect water during storms and release it slowly to your gardens or your lawn.

You can plant your garden with deep-rooted native plants.

You can replace impervious (non-porous) drives and walkways with pervious pavement or GI designs.

In addition to this introduction page, we have a number of Green Infrastructure resources for you to explore:




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