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Highlights • A model is proposed to evaluate runoff and AET of green roofs with a storage layer. • Daily ET and event runoff of green roofs decrease as ADP increases. • A storage layer enlarges the ability of green roofs to increase AET and reduce runoff. • The effects are pronounced under high temperature and rainy weather. • The effects of an additional storage layer have seasonal and yearly variations. Abstract Reduction in runoff and increase in actual evapotranspiration (AET) are two well-known benefits of green roofs. However, few studies have been carried out to investigate how green roofs affect runoff and AET when there is interaction between them. Such interaction is most prominent when green roofs have an additional storage layer. In this study, a modified hydrological model for green roofs is proposed to explicitly describe water retention and release in different layers and during wet/dry periods, which can reflect the interaction between runoff and AET under alternating dry and wet conditions. After calibration and validation with experimental data, the model was used to evaluate the combined effects of runoff reduction and increase in AET for green roofs under moist sub-tropical weather condition (such as Shenzhen, China). The results indicate that the daily AET and event runoff of green roofs decrease with increasing antecedent dry period (ADP); an additional storage layer can increase the ability of green roofs in reducing runoff and increasing AET. Generally, the effect is more pronounce under weather conditions with higher temperature, more rainfall amount and longer ADP. Such results provide hydrologists and engineers with a new and effective tool to simulate and understand the performance of green roofs by considering water retention and release in the layers. [ABSTRACT FROM AUTHOR]

• A continuous hydrologic model is tested using as input a long observed rainfall time series at 10-min resolution. • The proposed continuous model is tailored for small and ungauged basin applications. • The test results confirm that continuous models can be an appealing alternative to the event-based approach. The design hydrograph estimation in small and ungauged basins represents one of the most common practices and, yet, a challenging open research topic for hydrologists. When discharge observations are not available, the practitioner is compelled to apply empirical approaches. The rational formula is slowly disappearing, while event-based approaches are more and more widespread. A step forward is represented by continuous models that have the potential to address the major drawbacks of event-based approaches. In this work we applied a continuous model specifically designed for ungauged basins (COSMO4SUB) and tested its use in conditions where typically the rational formula and the event-based approaches are applied. Results confirm that the continuous modelling is suitable for rapid and effective design simulations supporting flood hazard modelling and mapping studies. [ABSTRACT FROM AUTHOR]