Low Cost Alternatives to “LID” (Low Impact Development)

As our culture, and more specifically, the development and design industries follow our movement into greater sustainability and “green” practices, more thought is necessary.  My observation of design is that many architects, engineers, landscape architects, planners, etc. have become very good at standardization of design.  We break down a project into components that a standard can be met and move on to the next step.  While this creates greater amounts of efficiency, it treats design elements as monotonous entities that could literally be anywhere.  This is also a common criticism of suburbia, where a subdivision in New Hampshire might look exactly the same as a subdivision in Phoenix, Fargo, Orlando or Kansas City.  It is not context sensitive to the culture and indigenous materials of its region.  We need to be more critical of the practice standards and consider alternatives for the basics such as curbs, paving and walls.

This "low impact" solution for storm water management in parking lots is effective in directing storm water to the plant material but can become very costly with excessive concrete curbs and curb cuts. Photo from Light Imprint Handbook by DPZ Charlotte.

I previously wrote a blog post about Light Imprint (LI) and its advantages in contrast to Low Impact Development (LID).  Light Imprint, as well as Steve Mouzon’s “The Original Green“, look at sustainable features in a holistic, more economical and historical manner.  I believe that there are a lot of merits and advantages of LID and its role in sustainability.  LID has opened the minds of the development industry to develop with more considerations for the environment.  Low-Impact Development standards for parking lot storm water management may call for curb cuts to allow storm water to infiltrate into the parking islands to add natural irrigation to plant material instead of simply directing the storm water into storm drains.  This is a great feature and it will save some costs in regards to irrigation for the plants, however it comes with a cost of not only constructing the curbs, but to construct them with strategically placed curb cuts.

This parking lot solution utilizes storm water management solutions for the rainwater at the point of contact rather than directing the water to other sources. Photo from Light Imprint Handbook by DPZ Charlotte.

In contrast, Light Imprint looks at the parking lot as a whole utilizing porous materials (crushed rock, not the expensive “porous asphalt”) which reduce the heat island effect and allow water to be absorbed before it can even become “storm water” during a light rain.  In lieu of the curbs and curb cuts, Light Imprint may utilize stone or another indigenous material to define the planting island and allow water to penetrate the island in the voids of the stone.  As seen in the image, trees in Light Imprint, may not even require their own island, but stand-alone in the porous paving material.

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3 Comments

  1. John, i fear you are not understanding that LID is both about achieving a goal (mimicing the hydrologic cycle), not mandating a particular technique toward achieving the goal. Both the raingardens and the porous pavements in the examples you provide above are examples of LID–let’s call them LID facilities–but so too are land use strategies like compact development and connected street grids. One may be more economical than the other, sure, but both are LID. See the Puget Sound LID Technical Assistance Manual for a full understanding of the suite of strategies that LID encompasses: http://www.psp.wa.gov/downloads/LID/LID_manual2005.pdf I’m still not sure how LI is different than LID other than it seems to be growing out of CNU. Interested in hearing more about the parsing though.

    I’d also be interested in hearing about why you think LID is a more expensive option? There’s plenty of research that shows just the opposite, and to say that it is more expensive without backing it up with some numbers seems like a disservice to the national community of practitioners, researchers and policy makers who have been advancing the practice and knowledge around LID.

    1. Hi Brice, thank you for the comment. I am familiar with the processes promoted by LID and am appreciative of the efforts of what LID promotes. Our built environment is in dire need of whatever we can do to effectively manage our resources. In my mind, the primary difference between what LID and LI (Light Imprint) are trying to accomplish is in the land use strategies. With Light Imprint, land and urbanism are valued much higher than LID. In the example that you sent, which I apologize I was only able to skim over, the illustrative land use patterns demonstrate a lot of what is considered to be conventional suburban development (or CSD). The graphics illustrate some alternatives to cul-de-sacs that appear to have as much, if not more concrete and large consumption of area for the detention/retention areas. Light Imprint dissuades the use of cul-de-sacs in favor of higher amounts of connectivity and greater optimization of the land.
      Please don’t get me wrong, LID is doing a great benefit to the development industry. In fact, my fear is that LID is almost too successful and its acceptance of CSD land use patterns will have an adverse effect on the industry. Condoning and enabling cul-de-sacs are not the answer to smart growth and in my opinion is a stretch from what should be considered “low-impact”.
      What has a greatest effect as “low-impact” on the environment, again my opinion, is to have the built environment situated for urbanity, mixed-use and walkability. This will create density and a healthy lifestyle where walking is not only encouraged, but the most feasible and opportune method of transportation. In turn, the density and urbanity created in one hamlet or village creates the option for untouched and preserved natural setting where ecology can be effective. The LID options create beautiful raingardens, but they are land consumptive in an area that could occupy another home, business, etc. that would assist in the urbanity of the place. The raingardens are also not as effective as the untouched, natural ecosystem, which urbanity allows due to the density in one location. The question about costs, not only relates to the difference in using a gravel or crushed rock parking lot compared to “porous” asphalt, brick, etc., but also relating to the consumption of land that could be used for a greater purpose.

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