| dc.description.abstract | Due to the increase of urban impervious area and frequent extreme rainfall, the drainage system may not be able to drain stormwater and thus cause flooding. Green roof has the rainfall retention potential. It is one of the effective solutions for flood management in recent years . We build a green roof observation system which including experimental group (green roof) and control group (no green roof) in National Central University to analyze the stormwater reduction of the green roof . The stormwater reduction indicators include retained volume, peak reduction and peak-delay time. Then observation data for half year was input into a green roof hydrological model (NTU-GR) for calibration and validation. After confirming the feasibility of the model, NTU-GR model was applied to simulate the historical three-year rainfall data for a more comprehensive analysis. In this study, the rainfall events are divided into large rainfall and small rainfall with a total rainfall of 20 mm as the threshold. The Nash coefficient of two kinds of events are 0.89 and 0.84, respectively, indicating NTU-GR model performs well in simulating the green roof hydrology under both large rainfall and small rainfall events. The results of stormwater reduction of the observation data shows that both the retained volume and peak reduction have an average performance of more than 50%, and the peak delay time is about 0 to 1 hour. Moreover, the model is applied to simulates all of the rainfall events in the past 3 years with different antecedent water content (AWC=40%, 30%, 20%, 10%). The results of stormwater reduction show that if the AWC of the green roof is below 30%, the retained volume and peak reduction ratio are more than 50% for 75% of the events. When the events of rainfall is less than 20 mm and the AWC of the green roof is below 30%, the retained volume and the peak reduction of the green roof will be more than 99.6%. When the events of rainfall is larger than 20 mm and the AWC of the green roof is below 20%, 50% of the events have a performance of more than 50% in retained volume and more than 60% in peak reduction. When the AWC is lower, the average of delay time is longer. It shows that the AWC and rainfall are the key factors affecting the stormwater reduction of the entire green roof. Green roofs have a certain degree of contribution to stormwater reduction when the AWC is low. Furthermore, this research also develops a simple formula that can quickly and reasonably estimate the retained volume of each rainfall events under a specific green roof′s AWC. | en_US |