What Are the Shortcomings with Low Impact Design (LID)?
Note to Reader:
The commentary below originated with Jim Dumont, Engineering Applications Authority for the Water Balance Model Partnership. His reflections for waterbucket.ca were prompted by a recent article written by Florida-based Lisa Nisenson, a prominent member of the Rainwater-in-Context Initiative.
Jim Dumont is also a member of the Rainwater-in-Context Initiative. His commentary provides relevant context for the upcoming seminar on Sustainable Rainwater Management: Mimic the Water Balance to Protect Watershed & Stream Health!
Titled Is Sarasota doing right by the Bay?, the article by Lisa Nisenson was published by This Week in Sarasota, a community newspaper. The catalyst for her article was a presentation on the Light Imprint to the Sarasota City and Sarasota Council Commissions in June 2013.
Light Imprint: An Alternative to LID
“Sarasota is seen as a leader in Low Impact Design (LID), but you offer Light Imprint as an alternative. What are the shortcomings with LID?,” Lisa Nisenson asked Tom Low, author of the Light Imprint Handbook. (Lisa Nisenson is also a waterbucket contributor. To read an article posted previously, click on Easy Ways to Manage Rainwater for Lower Bills and a Healthier Earth.)
“LID attempts to manage stormwater quality by using on-site design techniques (such as bio-swales and pervious pavers). The primary concern with LID is its origin in managing water in auto-centric development,” responded Tom Low. He is a registered architect and certified planner. He leads the research initiative on Light Imprint.
“Its’ techniques are applied without significant variation to conventional suburban residential and commercial developments and to some urban areas with suburban characteristics (such as Portland and Seattle). While advocating for sustainable stormwater management tools, LID offers only a limited set of techniques for suburban land uses.”
Light Imprint is….
“Light Imprint is a green approach to neighbourhood design. It is a design methodology that combines ecologically sensitive rainwater management techniques with community design principles,” explains Tom Low.
“Established in 2006, the Light Imprint methodology has expanded it’s educational outreach and professional contributions to become a recognized rainwater mitigation practice.”
“Light Imprint green infrastructure is compatible with urban design that emphasizes compact, mixed-use, pedestrian-oriented design, and environmental efficiency. It is designed to reduce community infrastructure costs.”
About the Rainwater-in-Context Initiative
“Rainwater-in-Context unites New Urbanism, rainwater/stormwater and watershed management, Smart Growth, water reuse, low impact, Light Imprint, and other sustainable practices toward a holistic approach to rainwater that utilizes the rural-to-urban transect and Charter for the New Urbanism,” states Colorado-based Paul Crabtree, leader of the Rainwater-in-Context Initiative.
To Learn More:
To read the complete interview by Lisa Nisenson, click on Is Sarasota doing right by the Bay?
For more about the work of Tom Low, click on Light Imprint Handbook Integrates Sustainable Green Infrastructure and Community Design
For back on the Rainwater-in-Context Initiative, click on Cross-Border Alignment: Connecting the Dots Between Land Use Planning, Development, Watershed Health AND Infrastructure Management
The View from British Columbia
“It is significant that Tom Low said ‘LID attempts to manage stormwater quality by using on-site design techniques’. This is far different than what we are trying to do in our headwater streams in British Columbia,”observes Jim Dumont.
“If the sole objective of LID is quality of the runoff, then the vision of the stream and its health are secondary and must be assumed to be entirely related to quality.”
What About the Stream?
“What ever happened to looking at the stream to determine what is happening and to identify its needs and to identify ways to keep it healthy? I believe that the approach of focussing on water quality is short-sighted and will prove to be only a part of the solution. It seems that everyone has forgotten the pioneering work of Richard Horner and Chris May in the late 1990s in Washington State.”
“Horner and May found that, in the headwater streams, the critical impacts were habitat destruction caused by changes in the hydrologic regime of the developing land. In particular, they found that the fisheries resource would be greatly impacted by alteration of habitat by erosion long before water quality became a problem. They also found that in urban areas water quality would become critical at high imperviousness levels; however, by the time that occurs the fisheries resource would already be severely impacted.”
“They found that habitat protection and maintenance of the hydrologic regime is much more critical that water quality in headwater streams,” emphasizes Jim Dumont.
Application of Science-Based Understanding
“If we are to apply science-based understanding, we must prioritize the problems and solutions based upon the condition of the stream. It is critical to look at the stream to see its condition and its needs, rather than assuming that one solution from another region is the only solution,” Jim Dumont continues.
“In a heavily built up area, water quality protection would be a worthwhile objective as the habitat would already be damaged. Undisturbed headwater streams require erosion protection and maintenance of the hydrologic regime – that means water balance first, and protection of water quality second.”
A Guiding Principle: Applicability and Transferability
“When we read articles such as the one about Sarasota, Florida, we must always question the reasoning behind the examples and the validity of applying those examples directly in our region. So often there is a perception that someone from afar must be technologically ahead; and therefore, that we should be learning from their examples and implementing their solutions,” observes Jim Dumont.
“Asking the question about applicability and transferability allows us to utilize the most appropriate solutions in a logical and pragmatic manner. We may then choose to adopt the standards if they are appropriate and if they are applicable to the specific stream or region. Alternatively, we may choose a different and more appropriate solution based upon the needs of the stream and watershed.“
“Choosing the most appropriate solutions (and intrinsic) is a fundamental approach that somehow folks seem to have forgotten,” commented Tom Low when he reflected on Jim Dumont’s commentary about applicability and transferability. “A simplistic attempt to redirect folks to this with Light Imprint is the on-line calibration tool that applies variables of slope, climate, soil, initial cost, long-term maintenance costs, and transect zones for selecting over 60 tools for paving, channeling, storage, and filtration.
What This Tells Us
“The fact that in British Columbia we already have urban land use densities that are….in the range of the goals stated by the Light Imprint leadership….actually means that we are leading, rather than following,” concludes Jim Dumont.
“The Canadians do appear to be ahead of the US in this field because the US EPA took a really bad approach to LID that was based on the premise that enforcing every site to the same standard would somehow fix the problems of water quality in the US,” stated Paul Crabtree when he reflected on Jim Dumont’s commentary.
“The USA EPA approach has done some good, but has several crippling drawbacks: a) analysis of the stream/watershed is not part of the protocol: b) sprawl and greenfield development are incentivized since compliance is easier for those development types: c) the regulations became enormously cumbersome (100’s of pages long) because the premise was arbitrary, not based on good science, and required tremendous negotiations in order to achieve passage: and d) the resultant implementation is usually an expensive quagmire that is hated by all except those who are profiting from it,” explained Paul Crabtree.
To Learn More:
Rainwater Management in a Watershed Context – What’s the Goal?
“Watersheds are not all created equal,” states Will Marsh at the second in the 2011 Comox Valley Seminar Series
Application of the “DFO Urban Stormwater Guidelines” has evolved over the past decade to protect stream health