Dipartimento di Ingegneria - Università degli Studi di Palermo, Viale delle Scienze, Ed. 8, 90128, Palermo, Italy.
J Environ Manage. 2023 Jan 15;326(Pt A):116643. doi: 10.1016/j.jenvman.2022.116643. Epub 2022 Nov 14.
Different low impact development measures have been proposed to make cities more flood-resilient, and recent literature is paying great attention to the evaluation of their direct benefits in terms of flood risk mitigation and the numerous co-benefits that they may offer. This study describes an experimental prototype of a technologically advanced multilayer green roof installed in a Mediterranean urban area (i.e., Palermo, Italy) and explores the results of an analysis of data collected over a one-year monitoring period by a complex sensors network. Multilayer green roofs, or "blue-green" roofs (BGRs), are characterized by a high water retention capacity compared to traditional green roofs due to the presence of an additional storage layer (blue layer), usually equipped with a valve that allows for regulating discharge outflow and water storage. Due to their recent development, BGRs are still scarcely explored in literature and have never been tested before in semi-arid environments, where they could represent valid measures to counter possible climate change and growing urbanization effects. In this study, the hydrological effectiveness of the experimental BGR is quantitatively evaluated by using appropriate indicators, based on the comparison between the hydrological response of the system and an equal size benchmark "grey" roof. The analyses are prevalently focused on the system's stormwater retention function, also investigating the relative contributions of the green layer and the storage layer to the overall retention capacity through the introduction of new BGRs specific indicators. Results emphasize the high impact of storms characteristics, antecedent soil moisture of the green layer, and initial water storage in the blue layer on the system's retention capacity. The overall mean retention rate for the experimental BGR, on average equal to 77% at the daily scale and 61% at the event scale, is comparable to the typical values of traditional extensive green roofs and could be further improved through a "retention-oriented" management of the outflow valve. The system was able to entirely retain almost half of the rainfall events occurred during the monitoring period and, for all the others, it was however extremely effective in reducing runoff peaks and delaying the hydrograph produced.
不同的低影响开发措施已经被提出以提高城市的抗洪能力，最近的文献也非常关注评估这些措施在减轻洪水风险方面的直接效益，以及它们可能带来的众多附带效益。本研究描述了一个安装在地中海城市（即意大利巴勒莫）的技术先进的多层绿色屋顶的实验原型，并探讨了通过复杂传感器网络在一年监测期间收集的数据进行分析的结果。多层绿色屋顶，或“蓝绿”屋顶（BGRs），与传统的绿色屋顶相比，由于存在额外的储水层（蓝色层），因此具有更高的持水能力，通常配备有一个可以调节排放流量和储水的阀门。由于它们是最近才发展起来的，BGRs 在文献中仍然很少被探讨，而且以前从未在半干旱环境中进行过测试，在这种环境中，它们可能是应对可能的气候变化和不断增长的城市化影响的有效措施。在本研究中，通过使用适当的指标，基于系统水文响应与同等大小的“灰色”屋顶的比较，定量评估了实验性 BGR 的水文有效性。分析主要集中在系统的暴雨截留功能上，还通过引入新的 BGR 特定指标，研究了绿色层和储水层对整体截留能力的相对贡献。结果强调了暴雨特征、绿色层的前期土壤湿度和蓝色层的初始储水对系统截留能力的高影响。实验性 BGR 的总体平均截留率，在日尺度上平均为 77%，在事件尺度上平均为 61%，与传统的扩展型绿色屋顶的典型值相当，并且可以通过对流出阀的“截留导向”管理来进一步提高。该系统能够完全截留监测期间发生的近一半的降雨事件，对于其余的降雨事件，它在降低径流峰值和延迟产生的洪水过程方面非常有效。
