Abstract
Background: Green roofs (GRs) technology has gained increasing interest in recent years since it offers multiple benefits to urban environments, citizens and buildings. Eco-covers can capture some water nutrient pollutants, filter air pollutants and moderate the urban heat island effect. Beyond these benefits, abundant literature stresses the role played by the GRs from the hydrological perspective. They allow to face the increasing stress on the traditional urban drainage systems by reducing the annual stormwater runoff. In light of this, the hydrological behavior prediction of a vegetated cover is essential for urban planners, policy makers and engineers in order to quantify runoff mitigation potential so as to optimize their application. Objective: The aim of the present research is to meet this need by testing the accuracy of Nash cascade model in predicting the stormwater production of GR systems. Materials and Methods: The proposed model has been calibrated against hourly data of thirteen rainfall-runoff events observed at two experimental sites, both located within the campus of the University of Salerno, southern Italy. Event scale model calibration, aimed at the identification of the storage coefficient parameter, has been based on the optimization of a number of error statistics. Results and Conclusion: Despite its simplicity, the investigated model appears adequately to be able to predict the runoff production from the experimental green roofs with a good degree of accuracy, as described by the Nash-Sutcliffe Efficiency index, which ranges between 0.54 and 0.94.
Highlights
In the last decades, there has been a widespread implementation of green roofs worldwide since they provide many benefits at economic, ecological and societal levels
The goodness-of-fit indices reported in the previous section allow defining how good the calibrated Nash cascade model is in predicting Green roofs (GRs) runoff
The aim of this paper was to evaluate the ability of Nash cascade linear model to replicate monitored runoff from two green roof test beds in the campus of the University of Salerno, southern Italy
Summary
There has been a widespread implementation of green roofs worldwide since they provide many benefits at economic, ecological and societal levels. More complex models are SWMS_2D [15] for water movement in two-dimensional variably saturated media and storage-routing models [16, 17] and Long-Term Hydrologic Impact Assessment-Low Impact Development 2.1 or L-THIA-LID 2.1 [18] Despite these methods produce very accurate results, they require intensive computational efforts, data availability and technical expertise. Parsimonious hydrological models that run on a base of little input information and few parameters are of much interest for urban landscape planner intended to explore the impact of green technologies in a particular environment From this perspective, methods for simulating the hydrologic and hydraulic behaviors of green roofs assuming they can act as simple reservoir could be advisable [19, 20]. Eco-covers can capture some water nutrient pollutants, filter air pollutants and moderate the urban heat island effect Beyond these benefits, abundant literature stresses the role played by the GRs from the hydrological perspective. The hydrological behavior prediction of a vegetated cover is essential for urban planners, policy makers and engineers in order to quantify runoff mitigation potential so as to optimize their application
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