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LID: We know what it stands for, but what does it mean?
David Casaletto
My career in the water quality business over the last 10 years has been focused on wastewater and failing septic systems. While I have been exposed and participated in many other environmental issues, I had never taken the time to really learn about Low Impact Development or LID. My chance to change that and learn in detail what LID means and how it can change how we look at stormwater came this month.
Ozarks Water Watch helped the Fay Jones School of Architecture, located in Fayetteville and part of the University of Arkansas, print a book entitled LID: Low Impact Development, a design manual for urban areas. I was asked to give a presentation on LID and I used this book as my reference. I will say I have learned a lot! In the chance there may be a few others like me that have not have the opportunity to really study what LID is all about, I would like to share some of what I have learned.
LID is about the relationship between water and urbanization - specifically stormwater runoff - and the role of "green" development in ensuring good water quality. "Green" in this context is more about green plants and less about the "green" way of life. While most of us in the United States are blessed with good drinking water, the US Environmental Protection Agency's Index of Watershed Indicators shows that only 16% of the nation's watersheds exhibit good water quality. Besides discharges from agricultural land uses and site construction, much of this can be attributed to nonpoint source pollution from urban stormwater runoff channeled by impervious surfaces - roofs, sidewalks, parking lots, and roads - during the "first flush" of a storm event. The first hour of urban stormwater runoff has a pollution index much higher than that of raw sewage! Stormwater runoff contains residues from household and lawn chemicals, oil, gasoline, brake fluid, asphalt products from roads and roofs, and heavy metals.
 | | Stormwater runoff |
Mother Nature really does know what is best and plants (scientifically known as a vegetated treatment network), using a soft engineering approach, will infiltrate, filter, store and evaporate stormwater runoff close to its source. We have to get out of the "pipe and pond" conveyance infrastructure that just channels runoff, including pollution, elsewhere through pipes, catchment basins, and curbs and gutters. We can, as nature always has, remediate polluted runoff through a network of distributed treatment landscapes - plants. The three key words are: slow - spread - soak. Slow the runoff down, spread it out and allow it to soak in and be treated.
Research has indicated that when impervious area in a watershed reaches 10%, stream ecosystems begin to show evidence of degradation and coverage above 30% can produce severe degradation. But the good news is that infrastructure can be designed to provide greater ecological and urban services at lower costs. With LID, streets no longer have to be ecological liabilities and stream and lake ecological functioning are enhanced. Water and land can be in harmony as nature intended. New LID practices based on ecological soft-engineering can mitigate the impacts of urbanization on the environment, particularly in the substitution of natural ground cover or porous media for impervious surfaces.
 
Pervious pavement
What I have found exciting is that everyone can participate in LID, from a property owner with a small lot to the largest municipality. A small rain garden placed next to a driveway or in the low part of a lot can reduce runoff by 30%. There are a complete tool box of LID facilities including constructed wetlands, riparian buffers, rain gardens, infiltration basins, pervious paving, vegetated roofs and retention ponds, just to name a few. In fact 21 LID facilities are explained in the LID Manual in detail. LID practices can be used for the building, the lot, the street and public open space.
 
Rain garden (on the left) and a Green Roof (on the right)
I would like to invite everyone to preview the LID manual at: http://uacdc.uark.edu . Just click on "download the book" above the "low impact development" box for a .pdf preview of the 225 page manual and you can order it online for $30. If anyone would like, I would be happy to give my 45 minute presentation on LID to your group or organization. LID, like other environmental practices, will require a change in our habits and thinking and like all change, it will take time, but it is a change worth making.
Quote of the Week
"Our space planning should take its cue from the patterns of nature itself - the water table, the floodplains, the ridges, the woods, and above all, the streams."
William Whyte, The Last Landscape
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