Knowledge Bank

Green infrastructure (GI) stormwater control measures (SCMs) such as bioretention cells and permeable pavements provide an opportunity to utilize ecological practices to mitigate stormwater runoff from impermeable surfaces while providing additional co-benefits. This infrastructure maximizes its potential when there is a long antecedent dry period (ADP) between events that allows for complete drainage of stormwater, thereby recovering the SCMs potential to treat the next rainfall event. However, there is still uncertainty as to how effective this infrastructure is when much short ADPs separate events and the bioretention media is still saturated from the previous rainfall event. The question persists as to whether there is any loss in performance when more water is conveyed through a bioretention cell over a shorter period and whether there is a minimum period between storms that bioretention cells should be sized to. This research provides data to quantify bioretention cells’ ability to treat stormwater from back- to-back rain events. This analysis utilized a dataset collected over 6 years through before, during, and following the installation of bioretention cells and permeable pavements in the Clintonville neighborhood of Columbus, OH. Using this data, storms with similar ADPs were grouped for comparison to quantify differences in the hydrograph characteristics are water quality performance before and after installation of green infrastructure. This study found that shorter ADPs lead to greater volumetric runoff coefficients and lower total suspended solids concentrations in the pre-GI phase; however, as ADPs increased in the post- GI phase, no significant differences were observed in the performance of the GI. In general, this study found that GI implementation leads to decreased runoff and peak flow rates from the watershed regardless of ADP, supporting the application of these practices at the watershed scale.