Extensive Green Roofs: Different Time Approaches to Runoff Coefficient Determination

Stormwater runoff in green roofs (GRs) is represented by the coefficient, which fundamental to assess their hydraulic performance and design drainage systems downstream. Runoff coefficient values newly installed GR should be estimated models that must feasible reproduce retention behavior as realistically possible, being thus adjusted each season climate region. In this study, suitability of a previously developed model for determination assessed using experimental data, registered over 1 year period. Results showed does not quite fit data obtained present was distinct with different conditions, revealing need develop new better adjustment, taking into consideration other variables besides temperature precipitation (e.g., early-stage moisture conditions matrix study area). were also determined time periods (monthly, weekly, per rain event) most adequate approach, considering practical uses coefficient. The monthly approach resulted lower (0–0.46) than weekly or event (0.017–0.764) determination. When applied long-term analysis, no significant differences when monthly, runoff, resulting on variation only 0.9 m3 annual runoff. This indicates use although suitable sizing systems, might used estimate performance. Overall, pilot extensive 0.4 m2 presented an volume 469.3 L, corresponding rate 89.6%, total 1089 mm. assessment scales major contribution future assessments, decision support tool.