WPSU WBGS Green Roof in Philadelphia

WPSU WBGS Green Roof in Philadelphia

Bird's-eye view of a green roof in Philadelphia

Cities such as Portland, Ore. and Philadelphia, covered in impervious pavement and skyscrapers, have turned to solutions like green roofs, such as the one pictured above, to alleviate flooding and stormwater runoff.

Image: Penn State Public Media
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