Picture for yourself a concrete-laden alley, with rainwater pooling in its eroded depressions. Tall buildings border the alley, making it a dark and potentially dangerous place. Constructed for cars, trucks and trash, the space is covered in filth. Few people find reason to walk here, save to toss their trash or take out their dogs.

Most major cities harbor hundreds of miles' worth of alleyways like this. Although originally intended to create easy access to garages and to keep garbage bins and dumpsters hidden from view, many alleys in urban spaces have become more of a hindrance than a utility.

But a movement to redesign alleyways into useful spaces is quickly changing them from nuisance to asset. Green Alley projects are taking off across the United States and Canada as a way to reclaim these spaces as filtration and collection centers for rainwater, open spaces and corridors for community members to walk and play, and green space for creating natural habitat or starting local composting efforts.

In Los Angeles, the Back Alley LA project plans to use “community-based landscape design and environmental engineering to transform nuisance alleys into lush green ribbons linking the city’s diverse neighbors together in a network of public spaces.”

The partnership of public agencies, community-based organizations, and USC’s Center for Sustainable Cities and Keck School of Medicine has conducted action-oriented research on alleys in LA and hope to influence the city to invest in the idea.

While connecting neighbors with open spaces may have been the project's initial inspiration for greening its alleys, Back Alley LA has found numerous benefits for greening alleys:

*Create recreational opportunities. Alleys are a vital land resource in many park-poor neighborhoods, where obesity is a major health problem. Transforming alleys into walkable, bikeable, playable spaces can supplement scarce park resources by using existing underused infrastructure.

*Reduce Crime. Many residents perceive alleys as unsafe. Improving lighting and making alleys attractive will help address safety concerns and encourage their use.

Back Alley LA has presented its research to policy makers, public officials, and community organizations, and included a series of case studies from other pilot programs already underway in cities like Chicago, Seattle, Baltimore and Vancouver.

Since the end of 2007, for example, the city of Chicago has built almost 50 Green Alleys. The city “has deemed the models so attractive that now every alley it refurbishes will be a green alley.” To encourage other cities take such action, The City of Chicago has created a manual called the The Chicago Green Alley Handbook, which includes some exciting ideas on how to integrate green alleys into downtown areas, neighborhoods and industrial parks. Here's a great page that shows how ideas like bioswales, cisterns, permeable pavement and dark sky lighting can all be incorporated into the picture:

What's happening in this image is a reinvention of the way we think about how we use space. Whether it's a small alley or an entire industrial park, the old ideas of covering every surface with asphalt are dying. What's apparent in the image above is that ideas about how to weave the natural world into the build environment are vibrant, alive and hold major benefits for our society and economy.

Image credit: USC's Center for Sustainable Cities and The Chicago Green Alley Handbook.