Green Parking Lots: A Solution to Polluted Runoff

By: Myles Banfield

Current gray infrastructure, such as pipe systems and sewers, can become overwhelmed in events of heavy rainfall8. With climate change and rising sea levels, this could become a more common problem. Roads and parking create large amounts of runoff with high concentrations of pollutants. Vehicular movement and natural rainwater paths transfer a wide variety of pollutants to roads and parking lots4. This pollution includes waste from septic systems, livestock operations, pets, and lawn care. These harmful pollutants are carried along roads by storm water and end up in lakes, rivers, wetlands, and watersheds. Annually, over 1,000 tons of pollutants in the form of highly toxic heavy metals are present in storm water runoff4. These toxic substances from contaminated runoff accumulate in the bodies of fish, amphibians, and other animals in the wildlife food chain3.

Green parking lots are an effective solution to the problem of polluted storm water runoff. Conventional parking lots consist almost entirely of impervious surfaces like concrete that do not allow for water to infiltrate the soil. Green parking lots incorporate one or many green technologies that aid in the absorption, filtration, and redirection of the heavily polluted runoff3. A study done on a watershed known as Alley Creek was undertaken in response to problematic water quality in a nearby community, resulting from storm water and sewage overflow. In this study, swales, porous pavement, retention basins, rain barrels, rain gardens, and cisterns were used.

According to the Alley Creek study, retention basins, swales, and porous pavement were shown to be the most effective green infrastructures in the low-density residential area. According to the study, retention basins—vegetated basins with controlled outlets which serve to slow runoff—reduced storm water runoff by the largest amount at 12 percent2. Through open channels and depressions, swales directed water into the retention basins. Runoff in the basins seeped back into the ground over a period of hours or days depending on the area in which it is placed. Porous pavement—a paved surface with many small permeable gaps—had the second largest impact with a reduction of about 7 percent2. Rain barrels which captured water for reuse had too small of an impact to make a noticeable difference. During this study, a process known as disconnection was also used. Disconnection creates gaps along impervious surfaces where storm water travels so that more water can absorb into the ground. This reduced storm water runoff by approximately 10 percent.

Each of the afore mentioned technologies can be either applied to green parking lots or used in combination with green parking lots. The variation in how much each green infrastructure technology reduces storm water can be attributed to many factors such as land use, soil type, soil imperviousness and other factors. Based on the results of the Alley Creek watershed study, porous pavement was the most effective type of green infrastructure used as it was the most versatile and most consistently produced the largest amounts of storm water reductions. Additionally, porous pavement is almost exclusively used in parking lots and driveways which is a testament to the potential effectiveness for the general use of green parking lots.

There are over 4 million parking spaces in New York City, with the average one being 180 square feet. This means that there is over 720 million square feet of paved parking spaces alone7 not including the remainder of the paved space that vehicles use to drive inside the parking lot. If these spaces were reconstructed with porous pavement the impact would be enormous. Although in some areas porous pavement was not the most effective green infrastructure method, the other green infrastructure methods can be used to make up for it. In the study the combined use of the various green infrastructure types reduced runoff by 30%. If we applied green parking lots on a city, state, or even national scale, we could see the same or greater results which would be a huge step in reducing our ecological footprint. By looking at the research and various studies done on green parking lots, we can determine which technologies are most effective in accordance with many environmental factors. Focused use in areas where the impact is substantial will reduce both short and long term costs and maximize the effectiveness of green parking lots. The use of green infrastructure is imperative for the reduction of polluted runoff and reduces reliance on current gray infrastructure. The many different green technologies that can be used make them a versatile and highly effective solution.



  1. Alves, Alida, et al. “Combining Co-Benefits and Stakeholders Perceptions into Green Infrastructure Selection for Flood Risk Reduction.” Environments, vol. 5, no. 2, 2018, p. 29., doi:10.3390/environments5020029


  1. Eaton, Timothy T. “Approach and Case-Study of Green Infrastructure Screening Analysis for Urban Stormwater Control.” Journal of Environmental Management, vol. 209, 2018, pp. 495–504., doi:10.1016/j.jenvman.2017.12.068.


  1. Environmental Protection Agency. “Green Parking Lot Resource Guide.” EPA, Environmental Protection Agency,


  1. Jiyeon, Choi, et al. “Selection of Cost-Effective Green Stormwater Infrastructure (GSI) Applicable in Highly Impervious Urban Catchments.” KSCE Journal of Civil Engineering, vol. 22, no. 1, 01 Jan. 2018, pp. 24-30. EBSCOhost, doi:DOI: 10.1007/s12205-017-2461-1.


  1. Kumar, Kuldip, et al. “In-Situ Infiltration Performance of Different Permeable Pavements in a Employee Used Parking Lot – A Four-Year Study.” Journal of Environmental Management, vol. 167, 2016, pp. 8–14., doi:10.1016/j.jenvman.2015.11.019


  1. Onuma, Ayumi, and Takahiro Tsuge. “Comparing Green Infrastructure as Ecosystem-Based Disaster Risk Reduction with Gray Infrastructure in Terms of Costs and Benefits under Uncertainty: A Theoretical Approach interncdkldsational Journal of Disaster Risk Reduction, vol. 32, Dec. 2018, pp. 22–28. EBSCOhost


  1. Kasziz, Noah “New York Has 81,875 Metered Parking Spaces, And Millions of Free Ones.” Streetsblog New York City, 22 Mar. 2011,


  1. Tsegaye, Seneshaw, et al. “Transitioning from Gray to Green (G2G)—A Green Infrastructure Planning Tool for the Urban Forest.” Urban Forestry & Urban Greening, Sept. 2018. EBSCOhost, doi:10.1016/j.ufug.2018.09.005.

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