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This study assesses the relative influence of four independent variables on green roof hydrological performance under rainstorm conditions. Twenty-four extensive green roofs representing all combinations of the following four design factors were used: native meadow species versus Sedum; mineral-based versus biologically derived planting medium; 10-cm versus 15-cm depth; and irrigation provided daily, sensor controlled, or not at all. From events covering the period May-October in 2013 and 2014, mean values were determined for the seasonal volumetric runoff coefficient (Cvol = 0.4), peak runoff coefficient (Cpeak = 0.12), and U.S. Natural Resources Conservation Service (NRCS) curve number (CN = 94). Irrigation had the largest overall impact: daily irrigation increased Cvol to 0.5 compared to 0.3 for systems with sensor-controlled or no irrigation. The biologically derived planting medium, composed of a high proportion of aged wood compost, made a significant improvement, maintaining Cvol of 0.3 compared to 0.4 for the mineral-based product in the modules without irrigation. A similar pattern was found in the NRCS curve numbers. [ABSTRACT FROM AUTHOR]

This study, conducted between 2010 and 2012, compares the winter quality of storm water outflows from one pervious concrete and two permeable interlocking concrete pavement systems with runoff from an asphalt control pavement. The permeable pavement systems were designed for partial infiltration with underdrains. During the winter, the pavements were plowed and, occasionally, salted. Analyses are based on samples of permeable pavement effluent and asphalt runoff collected for 19 events over two winter seasons. The permeable pavement systems performed similarly and provided excellent storm water treatment during winter months by reducing event mean concentrations (EMC) and total pollutant loadings for petroleum hydrocarbons, total suspended solids, metals (copper, iron, manganese, and zinc), and nutrients (total-nitrogen and total-phosphorus). The permeable pavements were also shown to provide temporary storage and create opportunities for the dilution of sodium and chloride in outflows. Road salt was identified as a pollutant source for numerous pollutants beyond sodium and chloride. Freezing conditions did not inhibit the functionality of the permeable pavement systems for storm water treatment. [ABSTRACT FROM AUTHOR]