LID and GI – What’s the Difference?

Every time I think I know the difference, I read something or hear something that contradicts my understanding.  I’m beginning to think that there is no difference and that’s why we always see Low Impact Development and Green Infrastructure written together as “LID/GI.”

I think I have a decent handle on LID (please correct me if I’m wrong).  My understanding is that LID is basically an approach to managing stormwater runoff that promotes the use of natural or natural-like systems to mimic post development hydrology as closely as possible utilizing or mimicking natural processes, resources and systems.

It’s really the term, Green Infrastructure, that still has me confused.  I finally came to rest a few months back at a definition that is connected to natural resources in an urban setting (wetlands, streams, forested areas, or other hydrologic “green” spaces and features).  It involves the protection and the utilization of these resources for the management of urban stormwater runoff, generally.

Mine is a definition that seems to be somewhat supported by EPA on at least one page of their website.  However, other EPA citations present GI in a more LID-like fashion, comparing its benefits and costs to gray infrastructure and describing GI in a way where LID could easily be inserted in its place.  It appears that both LID and GI are approaches and not elements or features of an urban landscape.

I held strong to my understanding for a while, and even shared this with others less informed than myself (there are few out there).  But the terms and their inconsistantly applied loose definitions keep popping up.  I don’t mind being wrong every once in a while.  But I do like to make things right and correct before moving forward in most cases.

Looking again at EPA’s website discussions for each approach, I am certain of just a few things.  I see that EPA considers the two terms to be separate and distinguishable from one another.  Both are approaches to stormwater management; both seek to treat runoff at or near its source; both use, mimic, and seek to preserve natural features; and both are characterized as sustainable stormwater practices.  So what’s the difference?

“LID/GI” is a common occurance in EPA and state issued MS4 permits.  I knnow that it’s generally a wise practice to understand terminology against which you are regulated.  I thought I understood.  But now I’m not so sure.

Stormwater Experts, please set me straight.  Share your understanding and definitions of LID and GI. 

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One thought on “LID and GI – What’s the Difference?

  • I was hoping that GI would come to be the aspect of LID emphasizing capture/reuse – similar to the Aussie’s water-sensitive urban design (WSUD) paradigm. I agree that the GI/LID distinction is muddied to the point of non-differentiation.

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