In the first two installments of this series, we presented basic information about what LID is and how it works. In this piece, we’ll show that LID isn't simply a stormwater management technique, but a systems approach that provides multiple benefits addressing both public and private sector interests. To help you decide if LID may be right for your community, and with our apologies to David Letterman, we present:
Part III: The Top Ten Benefits of Low Impact Development
10. Low Impact Development blends into the landscape.
By integrating LID Integrated Management Practices (IMPs) into site design accounting for both specific site conditions and overall conditions in the watershed, one can achieve an overall site design that is functional, appropriate, and aesthetic. Some of the most commonly used IMPs include: permeable pavement; rainwater harvesting (rain barrels and cisterns); bioretention (greenways, riparian corridors, vegetated swales, percolation trenches, and rain gardens); green roofs; and level spreaders which can be incorporated into site design, parking lots, and native-species landscaping.
LID also makes the maximum use of existing natural systems. Wetlands can be used for natural water filtration, and streams can be reconnected to floodplains for storage of floodwaters. Using natural systems allows the least cost alternative, providing a class of benefits known as “ecosystem services,” for which benefits can be monetized as either avoided costs or direct benefits.
9. LID mimics the natural system.
Communities can use LID to overcome stormwater impacts caused by urbanization. Lot-level application of IMPs can provide similar functions of the natural hydrologic system composed of stream, riparian corridor, wetlands, and floodplains by retaining stormwater on site and allowing it to recharge groundwater -- slowly releasing it to surface water, or capturing it onsite for future use in irrigation. In this way LID creates a built environment that functions much more closely to the way the natural environment works.
The result is a landscape that generates less surface runoff, less water pollution, less erosion, and less overall damage to streams, rivers, and lakes.
8. LID provides aesthetic benefits.
In particular, stream buffers, bioretention facilities, greenways, and green parking lots can provide attractive and aesthetically-pleasing greenspace that is publicly accessible or simply part of the streetscape. This aesthetic character in turn contributes to livability, value, sense of place, and overall quality of life.
7. LID reduces flood risk.
IMPs function effectively to capture the first 1.5 to 2 inches of rainfall runoff, which is 75 to 95 percent of the rainfall events in most location in the United States. Urbanized and urbanizing watersheds can experience localized flooding during these rainfall events due to the amount of impervious surface that accompanies development. LID captures this runoff and retains it on site, rather than allowing it to flow downstream into streets or nearby properties.
6. LID provides multiple ecological benefits.
IMPs reduce the amount of impervious surface; increase the amount of groundwater recharge; cool stormwater runoff before it enters and impacts streams; reduce the amount of nonpoint source pollution reaching streams; decrease the heat island effect in urbanized areas; provide improved wildlife habitat; and even reduces smog. For an excellent overview of these ecological benefits, see the EPA’s Low Impact Development (LID) "Barrier Busters" Fact Sheet Series.
5. LID increases quality of life.
Installing LID provides additional greenspace for communities, as well as providing the opportunity to create green corridors to link existing greenspaces or other community destinations. Numerous public health studies have identified that increasing the amount of greenspace creates a marked improvement for both mental and physical health, particularly in urbanized areas.
4. LID promotes economic competitiveness.
LID’s contribution to a community’s quality of life, the cost effectiveness of the technology, and the flood risk reduction work together to enhance a community’s attractiveness -- appealing to new residents and business owners as a place to live and do business. Homebuyers’ willingness to pay is one indication of economic competitiveness. In Apex, North Carolina, the amenity values in the Shepards Vineyard housing development added $5,000 apiece to the price of 40 homes adjacent to the regional greenway. Despite this price differential, the greenway-fronting homes were the first to sell. See Rails-to-Trails Conservancy report, Trails & Economic Development (pdf; 2007).
3. LID improves community resilience to climate change.
Changing climate will result in more extreme weather events, which will impact communities’ ability to respond to conditions like droughts and floods. Low Impact Development provides the “bend but don’t break” flexibility needed by infrastructure to endure the impacts of unforeseen weather conditions.
2. LID is cost effective.
Cost comparisons show that LID is typically less expensive than conventional stormwater management systems to construct and maintain. Why is that the case? In large part because of the need for fewer pipes, fewer below-ground infrastructure requirements, and less impervious surface that has to be maintained.
- Pilot project estimates suggest that LID projects can be completed at a cost reduction of 25 to 30 percent compared to conventionally developed projects. See Low-Impact Development: Lot-level approaches to stormwater management are gaining ground (pdf), by Mary Catherine Hager (Stormwater: The Journal for Surface Water Quality Professionals; Jan/Feb 2003).
- A bioretention system developed along the Anacostia River in Washington, D.C. saved $250,000 over centralized collect-and-treat technology. See Low Impact Development Retrofit Approach for Urban Areas (p. 102, pdf), by Neil Weinstein (The Low Impact Development Center).
- Studies conducted in Maryland and Illinois have shown that new residential development using LID infrastructure stormwater controls saved between $3,500 and $4,500 per lot (1/4-1/2 acre) compared to new development with conventional stormwater controls. See Rooftops to Rivers: Green Strategies for Controlling Stormwater and Combined Sewer Overflows (p. 12; pdf), by Christopher Kloss & Crystal Calarusse (Natural Resources Defense Council; 2006).
- The Congaree Bottom Hardwood Swamp outside Columbia, South Carolina provides ecosystem services; that is, it serves as a natural water quality improvement facility by filtering toxins, sediment and nutrients from stormwater runoff. Replacing this natural system with centralized collect-and-treat infrastructure would cost $6.7 million in 2003 dollars. See Conservation Benefits: Putting Value Where it Belongs (p. 16; pdf), by Bill Berry (National Association of Conservation Districts; 2010).
- A study of the Village Homes development in Davis, California -- one of the earliest large-scale housing developments incorporating low-impact development practices -- concluded that by using vegetated swales, narrow streets, and a cluster layout of building lots, the developer saved $800 per lot, or $192,000 for the development. Cited in The Economics of Low-Impact Development: A Literature Review (p. 11; pdf), by Ed MacMullan & Sarah Reich (ECONorthwest; 2007). Editor's note: see my conversation with Judith Corbett, co-developer of Village Homes. For more about Village Homes.
- The reduced pavement and increased natural vegetation at Village Homes has also been found to reduce home energy bills by one-third compared to surrounding neighborhoods. See Village Homes: A Case Study In Community Design (pdf), by Mark Francis (Landscape Journal 21:1-02; 2002).
1. LID increases property values.
Various studies have quantified the positive impacts of LID on property value, as well as re-development potential and greater marketability. Space once dedicated to stormwater ponds under a conventional development scenario can be used for additional development to increase lot yields. This “found space” can be retained in conservation as a greenspace amenity, which can also increase property values.
- The Gap Creek subdivision in Sherwood, Arkansas revised an original subdivision plan and included LID techniques. Open space was increased from 1.5 acres allocated in the original plan to 23.5 acres in the new LID plan. Lots sold for $3,000 more and cost $4,800 less to develop, resulting in $2.2 million additional profit to the developer.
- The Auburn Hills subdivision in Wisconsin used LID stormwater management, preserved 40 percent of the site as open space, and saved $761,396 -- even with the inclusion of higher landscaping costs for LID development. [id, p. 12]
These two developments are among more than a dozen discussed in the EPA's excellent report, Reducing Stormwater Costs through Low Impact Development (LID) Strategies and Practices (pdf; December 2007).
Property value benefits extend beyond what is directly gained by developer and property owner. The water quality improvements resulting from LID practices directly benefit communities by increasing real estate value, which in turn, protects tax revenue.
Energy savings and decreased flooding associated with LID also help to boost property values. Even a small reduction in flood risk increases property values by up to five percent. Cited in The Economics of Low-Impact Development: A Literature Review (p. 18; pdf), by Ed MacMullan & Sarah Reich (ECONorthwest; 2007).
There you have it -- counting down from 10 to 1 -- reasons to consider incorporating Low Impact Development practices in your community.
Jim Segedy, FAICP, worked for many years in Ball State University's Community Based Planning program, providing assistance to more than one hundred communities and many plan commissions (as planning commissions are called in Indiana). He is currently an adjunct Professor of Urban Studies at the University of Pittsburgh; and a member of the Edgewood, Pennsylvania, Planning Commission.
Lisa Hollingsworth-Segedy, AICP, is the Associate Director for River Restoration for American Rivers' Pittsburgh field office. Before moving to Pennsylvania, she spent over a decade as a circuit-riding planner for a regional planning organization serving the western fringe of Metropolitan Atlanta.