Stormwater Symposium


397485 - Exploring Factors Affecting Hydrological Performance of Permeable Pavements

Monday, June 4
4:00 PM - 5:30 PM
Location: Greenway AB
Co-Authors: Jay Dorsey, Columbus, Ohio – Ohio State University; Alessandra Smolek, Cary, NC – WithersRavenel; William Hunt, Raleigh, NC – North Carolina State University

Permeable pavements benefit urban hydrology through detention of stormwater in the aggregate base and subsequent exfiltration to the underlying soil. The majority of previous research has focused on permeable pavements constructed in sandy soils and/or treating only direct rainfall. Four permeable pavements employing internal water storage (IWS) zones, treating a variety of run-on ratios, and situated over low permeability soils were intensively monitored for their hydrologic performance in northern Ohio. Volume reduction varied from 16% to 53% for permeable pavements with low drawdown rates (<0.35 mm/hr) and loading ratios ((Watershed Area+Permeable Pavement Area)/(Watershed Area)) exceeding 5:1. For the permeable pavement which treated only direct rainfall, runoff volume was reduced by 99% through exfiltration and evaporation. Post-construction drawdown rates were similar to underlying soil saturated hydraulic conductivity (Ksat) measured during construction, suggesting lateral exfiltration and evaporation were relatively minor contributors to volume reduction. Stormwater was completely captured (i.e. no discharge from the permeable pavements) during 4-80% of observed storm events. Average depth of abstraction ranged from 3.0 mm (site with highest loading ratio) to 25.2 mm (site treating only direct rainfall). Substantial peak flow mitigation was observed for all rainfall events not producing surface runoff (i.e. untreated bypass). Peak flow rate was diminished by more than 80% for 7 events exceeding the 1-year, 5-minute design rainfall intensity for Cleveland, Ohio. Lower loading ratios, reduced surface runoff, an IWS zone, and higher underlying soil Ksat directly impacted volume reduction and peak flow mitigation. Overall, permeable pavement mitigated negative hydrologic impacts of impervious surfaces even when sited over low conductivity clay soils.

Ryan Winston, PhD, PE

Research Assistant Professor
Ohio State University

Dr. Ryan Winston is a Research Assistant Professor in the Department of Food, Agricultural, and Biological Engineering at the Ohio State University. For the past decade, his research has focused on hydrologic and water quality improvements provided by Low Impact Development (LID) strategies, with particular interests in bioretention, permeable pavement, and highway runoff management. Recently, much of his work is related to utilizing Low Impact Development in the municipal right-of-way to reduce sanitary sewer overflows. Over the past ten years, Ryan has published 29 peer-reviewed journal articles, instructed several college courses, and taught over 100 workshops related to stormwater management to professionals. These include several international workshops, including one in Singapore and another in Nanjing, China. Ryan is a Professional Engineer in both Ohio and North Carolina. He has much engineering design experience related to LID, and has designed, installed, and monitored (for research purposes) stormwater controls in six U.S. states. He also has experience in construction observation/supervision and maintenance of LID practices.


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