Fitzsimmons 1 Low Impact Development as a Tool in Sustainable Land Management Abstract This paper presents research on low impact development, or LID, a method of sustainably managing stormwater through designs that utilize natural processes for filtration, infiltration, and redirection of stormwater. The water quality and quantity issues associated with urban areas and climate change are explained as a context for LID as well as the history of its use in the United States. Likewise, the barriers and benefits associated with LID are further explained to clarify typical misconceptions and assumptions. I also use examples of successful implementation of LID technology on both the east and west coasts to illustrate how different techniques can coordinate with each other in different climates; correspondingly, I include an example in the Midwest in which LID techniques have not been established but are highly recommended by scientists. The literature shows that LID is an extremely viable tool for furthering sustainability through land use design and regulations. Even so, at this point in time and politics, methods like LID are not widely accepted enough to be required or even regularly used in planning. However, as climate change effects continue to worsen, LID techniques and similar tools will soon become an undeniable necessity in land management. Optimistically, this change in land use law and policy will occur before anthropogenic climate change becomes irreversible.
Introduction Context and History Science has proven not only that climate change is real but that it is anthropogenic. The rapidly increasing human population coupled with unsustainable consumption are creating environmental issues on both local and global scales with water quality and quantity as some of the most severe challenges. In particular, the rapid urbanization associated with population growth is a major offender in stream degradation due to increasing impervious cover – including but not limited to roofs, roads, impervious canals, and parking lots – and stream burial from development (Martin-Mikle et al. 29; Pyke et al. 166). These actions result in inconsistent water flow, higher flooding, rapid movement of water, more erosion, less infiltration and filtration of water, more water pollution, and general disruption of watersheds and hydrological ecosystems (Martin-Mikle et al. 29). This stream degradation that occurs because of improper city
Fitzsimmons 2 stormwater management is called “urban stream syndrome” (Pyke et al. 166). One of the widely used responses to these issues is LID. Although LID techniques have been successfully utilized in both Asia and Europe for many years, the United States has only caught on to the benefits and practicality of LID within the last few decades. What is experimental and fresh to American planners, engineers, and architects is tested and proven to the rest of the world. In the United States, LID at the municipal level was pioneered in the 1990s by Prince George’s County in Maryland. The county initially constructed bioretention cells, but after their success, the county expanded their LID use and by 1998, they had published the first municipal manual for LID, which would be expanded and published on a national scale just two years later. Since then, research and implementation of LID techniques have expanded and improved across the US (Guillette “Achieving”; Prince). Definition and Purpose As defined by the US Environmental Protection Agency, LID consists of “systems and practices that use or mimic natural processes that result in the infiltration, evapotranspiration or use of stormwater in order to protect water quality and associated aquatic habitat” (“Urban Runoff”). In other words, LID is an alternative method of stormwater management that uses both natural and engineered techniques to filter, store, and direct stormwater, which conserves, maintains, and restores watersheds (Guillette “Low”). LID falls under the broader categories of green infrastructure – physical infrastructure built with the natural environment as a priority – as well as source-control technology because it manages the stormwater where water is generated rather than right before it re-enters the hydrologic system, like in conventional stormwater management (“Urban Runoff”; Guillette “Achieving”). Also unlike conventional methods, which heavily concentrate stormwater runoff in retention ponds, LID strategies distribute stormwater evenly across a site so that the water can be better absorbed into groundwater (Guillette “Low”). Low Impact Development Tools LID techniques vary widely in method, cost, and design, but they are often used together to meet different needs, thus creating a comprehensive stormwater management system. The most common LID technologies are listed in Table 1 below with indications of what they contribute to stormwater management (Guillette “Low”).
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(Guillette “Low”) Benefits and Barriers Overall, LID is considered a sustainable and holistic approach to stormwater management, especially in the face of climate change. In fact, research shows that LID techniques are more effective than conventional strategies at managing and cleaning stormwater runoff based on historical precipitation data as well as simulations of various future precipitation loads based on climate change effects (Pyke et al. 170). Specific benefits of LID include: •
Elimination of the costs associated with retention ponds, curbs, gutters, pipes, and inlets
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Reduced long-term costs
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Increased property values and marketability
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Increased lot yield with the elimination of large retention ponds (Guillette “Low”)
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Groundwater and surface water conservation
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Efficient and cost-effective water management
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Community beautification
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Improved ecosystem health (Guillette “Achieving”) However, LID does still present challenges, especially in countries without a long history
of utilizing this tactic, such as the US. The four most common barriers to LID include high costs, long-term maintenance, delayed permit approval timelines, and misconceptions of what LID is (Frederick et al. 17). LID is generally assumed to be more expensive than conventional management; however, costs vary widely by design. For instance, a vegetated bio-swale costs about $0.50 per square foot for both design and construction, whereas a green roof is described as the “LID practice with the greatest capital cost, compared with its conventional alternative,” at $10-$25 per square foot for installation (Guillette “Low”; Frederick et al. 22; Taylor). Because of the money saved from avoiding hard infrastructure installation, like curbs and impervious canals, LID can sometimes be cheaper than conventional design. Other times, the construction and maintenance costs will be higher, but the LID design will last longer, manage the stormwater more effectively, and provide other benefits (Frederick et al. 21-22). Likewise, maintenance is necessary for LID designs to be continually effective, but conventional infrastructure also requires its own, very expensive maintenance. And, again, with proper maintenance, the LID method will last longer and reap more benefits than conventional infrastructure (Frederick et al. 22-23). The third challenge, delayed permit approval times, is a cost associated with government operations rather than LID itself; this can be overcome by municipalities incorporating LID techniques into their land use law, dedicating funds and staff toward LID installations and maintenance, and promoting its use with incentives (Frederick et al. 24). Lastly, many misunderstand LID as a very narrow technique limited to certain climates and soils; however, LID includes a wide variety of tools that can be adapted to hot, cold, or temperate climates and sandy or clay soils. These techniques have been successful in all types of environments (Frederick et al. 17-21).
Examples As noted above, Prince George’s County in Maryland is considered one of the pioneers in LID in the US. Their fame began in 1995 when a developer incorporated LID technologies into a 60-acre development in the Somerset Community. The development replaced curbs and gutters with bioswales along the streets and rain gardens, or bioretention cells, in each yard; these stored
Fitzsimmons 5 and filtered rainwater, allowing it to infiltrate the soil across the entire site rather than directing stormwater runoff to one large retention pond. Additionally, downspouts directed roof water into either rain barrels or vegetated areas, where the water was reused to irrigate plants. Even though the development still had unusually wide, impervious streets, the developer’s successful use of LID techniques allowed for six additional lots and a subsequent savings of $916,382 as well as long-term, sustainable stormwater management for the community (Guillette “Low”; Prince). As another example, Olympia, WA, has shifted to LID in order to preserve their Green Cove Basin. This involved changing policy to first designate the Green Cove Basin and Creek as an environmentally sensitive area, to require certain LID designs in that area, and to encourage development away from the basin. Olympia achieved this largely by encouraging increased density and pervious surfaces. The city increased the allowed density and building heights, changed zoning to allow multiple uses, and reduced setbacks and lot widths. Additionally, they limited street widths and parking lot sizes while also requiring pervious materials in newly constructed parking as well as increased minimum tree density (Guillette “Achieving”). By contrast, research at the University of Oklahoma on the Lake Thunderbird watershed illustrates that LID techniques strategically placed in hydrologically sensitive areas within the stream network would be beneficial to the watershed, but LID is not being implemented. The Lake Thunderbird watershed is a mixed-use watershed, so it has both urban as well as agricultural pollutants. In particular, the watershed suffers from high amounts of nutrient input, which causes eutrophication. The authors’ calculations indicate that LID could reduce nutrient pollution in Lake Thunderbird by up to 17%. However, effective installation and maintenance of LID technologies rely heavily on local governments’ willingness to commit funds and staff, which often prevents LID from being implemented in places like Oklahoma (Martin-Mikle et al. 29-39).
Implications for Planning Practice Although most of the literature contextualizes LID solely as a sustainability tool, it also is inherently linked to land management, especially in the prevention of and reaction to climate change effects. Currently, LID fits into planning and land regulations as an optional best practice rather than a requirement in most US cities. Undue politics surrounding climate science prevents sustainable land management methods like LID from being incorporated into land use law.
Fitzsimmons 6 However, as anthropogenic degradation of the environment and global climate change continue to rapidly increase, sustainability will inevitably need to become a priority in planning for many reasons like mitigating the costs of natural disasters, decreasing energy use, conserving natural resources, meeting stricter environmental regulations, and meeting basic needs as well as improving general quality of life. The built environment and land use policy heavily influence all these factors and more, including stormwater management, and LID is one of the tools that will likely be required for planners to utilize soon with increasing awareness, acceptance, and effects of climate change.
Fitzsimmons 7 Works Cited Frederick, Rod, et al. “Overcoming Barriers to Implementation of LID Practices.” Low Impact Development Technology – Implementation and Economics, American Society of Civil Engineers, 2015, https://app.knovel.com/hotlink/toc/id:kpLIDTIE01/low-impactdevelopment/low-impact-development. Accessed 19 April 2021. •
This article is from a book of compiled articles and research from the 2011 Low Impact Development Conference. The authors address the main challenges associated with low impact development, including increased maintenance and cost, delayed permit approval timelines, and misconceptions of how low impact development functions. First, the authors clarify that low impact developments consists of more than filtering water through vegetation and permeable soils; there are various low impact development techniques that are flexible to different climates and soil types. The authors also discuss the costs and maintenance associated with low impact development. They assert that although low impact development has more upfront costs and requires more regular maintenance, the long-term durability and benefits of low impact development ultimately make it the more financially smart choice. The authors also assert that governments should treat low impact development as their responsibility when managing stormwater, dedicating proper funds for implementation and maintenance and communicating swiftly so that developers can get permits in time. The authors also briefly discuss examples of public education efforts that have helped residents and developers accept low impact development more and encourage its use.
Guillette, Anne. “Achieving Sustainable Site Design Through Low Impact Development Practices.” Whole Building Design Guide, National Institute of Building Sciences, 2 Aug. 2016, https://www.wbdg.org/resources/achieving-sustainable-site-design-through-lowimpact-development-practices. Accessed 18 April 2021. •
This article is also written by Anne Guillette, a LEED accredited professional who works in the Low Impact Design Studio. This article focuses more on the history and administration of low impact development strategies; it also delves a little more into the purpose and benefits of low impact development. Notably, the article includes a diagram of the low impact development process as well as a list of specific tools. The author also
Fitzsimmons 8 briefly describes several examples of towns that have implemented low impact development in planning. ---. “Low Impact Development Technologies.” Whole Building Design Guide, National Institute of Building Sciences, 3 Nov. 2016, https://www.wbdg.org/resources/low-impactdevelopment-technologies#:~:text=A.,water%20where%20it%20is%20generated. Accessed 18 April 2021. •
This resource is a very comprehensive in describing low impact development. The author defines low impact development while also providing graphic and written examples. She also compares low impact development with conventional stormwater management and explains its advantages over conventional strategies. The article includes a table that brushes on a multitude of low impact development techniques followed by in-depth explanations of the most common of those. There is also a list of related regulations and laws and additional resources at the end of the article. The author is a LEED accredited professional who works in the Low Impact Design Studio.
Martin-Mikle, Chelsea, et al. “Identifying Priority Sites for Low Impact Development in a Mixed-Use Watershed.” Landscape and Urban Planning, Elsevier, vol. 140, 2015, http://dx.doi.org/10.1016/j.landurbplan.2015.04.002. Accessed 20 April 2021. •
This article is based on research done on the Lake Thunderbird Watershed, which is a mixed-use watershed, to determine a methodology for strategic placement of low impact development. The authors note that a lot of low impact development is done in rural areas, but a lot of stream and water degradation, or “urban stream syndrome,” occurs because of rapid urbanization, which is why they have focused their research on a mixeduse watershed that encompasses several cities. The authors base their method on public data of hydrologically sensitive areas (HSA) as well as site-specific factors of impervious surfaces, spatial scale, land use, and proximity to the stream network, so it is replicable in other regions. The authors determine that low impact development has potential to significantly reduce eutrophication, which is a particular problem for the Lake Thunderbird Watershed, and reduce general stream degradation; in particular, they note that low impact development would be an important tool for planners in regulating land use and environmental health as well as meeting federal environmental regulations.
Fitzsimmons 9 However, the authors also note that the efficacy of low impact development depends heavily on policy and distribution of funds to support it. Prince George’s County Department of Environmental Resources and Programs and Planning Division. Low-Impact Development Design Strategies: An Integrated Design Approach. Prince George’s County, MD, June 1999, http://cdnassets.hw.net/6f/66/e6cf4a584c8bb6573dc63d10ad6a/lid-national-manual.pdf. Accessed 18 April 2021. •
In another source (Guillette), Prince George’s county is described as a pioneer in low impact development because of their early integration of low impact development techniques, at least for the US. About a decade after doing this, they also published the first municipal guide to low impact development, which is this source. This manual’s topics include low impact development goals, site planning, hydrologic analysis, integrated management, erosion control, and public outreach.
Pyke, Christopher, et al. “Assessment of Low Impact Development for Managing Stormwater with Changing Precipitation Due to Climate Change.” Landscape and Urban Planning, Elsevier, vol. 103, 2011, https://doi.org/10.1016/j.landurbplan.2011.07.006. Accessed 20 April 2021. •
This article from the academic journal Landscape and Urban Planning consists of a quantitative study that determine stormwater runoff amounts based on the amount impervious cover, intensity, and precipitation. In particular, this study focuses on how low impact development techniques compare to conventional techniques based on both historical precipitation data as well as predicted precipitation data that will change due to climate change. The authors find that stormwater runoff is most sensitive to impervious cover amounts, then precipitation amount and then intensity. The data also indicates that low impact development is overall superior in mitigating stormwater runoff to conventional techniques. The authors, therefore, conclude that low impact development techniques, especially ones concerning impervious surfaces, will be valuable tools as communities must adapt land use to climate change.
Taylor, Mia. “What a Green Roof Costs You on the Way to Saving Everything.” TheStreet, TheStreet, Inc., 22 May 2015, https://www.thestreet.com/personalfinance/mortgages/what-a-green-roof-costs-you-on-the-way-to-saving-everything-
Fitzsimmons 10 13161050#:~:text=The%20EPA%20estimates%20that%20the,to%20%241.50%20per%2 0square%20foot. Accessed 21 April 2021. •
This news article discusses green roofs, particularly the costs and benefits associated with them. I simply used this article for a dollar estimate of the cost of green roofs because on of my other sources stated that it was the most expensive low impact development technique.
“Urban Runoff: Low Impact Development.” Polluted Runoff: Nonpoint Source (NPS) Pollution, United States Environmental Protection Agency, 7 Oct. 2020, https://www.epa.gov/nps/urban-runoff-low-impact-development. Accessed 20 April 2021. •
This article briefly explains what low impact development is, its purpose, and various techniques to achieve it. More importantly, this page also includes a list of links to eleven short, helpful documents that discuss various barriers of low impact development and how they can be overcome, including cost, maintenance, applicability to different environments, space restrictions, and others.