Hydrologic Characteristics of Low-Impact Stormwater Control Measures at Two Sites in Northeastern Ohio, 2008–13

Abstract

This report updates and examines hydrologic data gathered to characterize the performance of two stormwater-control measure (SCM) sites in the Chagrin River watershed, Ohio. At the Sterncrest Drive site, roadside bioswales and rain gardens were used to alleviate drainage problems in this residential neighborhood area. At the Washington Street site, a treatment train (including a pervious-paver system, rain garden, and bioswales) was used to reduce and delay stormwater runoff at a small business development. Selected metrics were used to demonstrate SCM system performance with regard to stormwater-management objectives at each site. Rain-garden overflow-frequency data collected at the Sterncrest Drive site during 2008–13 were used to characterize system sensitivity to rainfall characteristics. Approximately 70 percent of storms exceeding 0.75 inches during 3 hours or more resulted in overflows. Drainage-design features that may restrict flow through the system were identified. Overall, the data and local observations confirmed the continued success of the SCM at the Sterncrest Drive site in preventing roadway closure due to flooding. The additional years of data collected at the Washington Street site indicated that a previous analysis of increased runoff removal, based on only the first 2 years (2009–10) of data, provided premature conclusions. With 5 years of data (2009–13) and adjusting for changes in rainfall characteristics, it appears that the percentage of runoff removed by the system is decreasing; however, the lag time (time from onset of rainfall to runoff) has remained nearly constant. The annual mean percent removal for 2010–13 ranged from 55 to 37 percent with an overall mean of 45 percent, and this does meet the project objective of reducing runoff from the business complex. One possible explanation for the combination of increased volume of runoff and no change in the timing of runoff is the preferential flow paths developed in the SCM, increasing the capacity for internal drainage. Data indicated that the SCM system at the Washington Street site had reduced functionality over time.

First posted March 20, 2015