Paved surfaces, increased precipitation intensities in addition to limited capacity in the sewer systems, cause a higher risk of combined sewer overflows (CSOs). Sustainable drainage systems (SUDS) offer an alternative approach to mitigate CSO by managing the stormwater locally. Seven SUDS scenarios, developed based on the concept of effective impervious area reduction, have been implemented in the Grefsen catchment using theMike Urbanmodel. This study evaluated the hydrological performance of two SUDS controls (i.e. green roof (GR) and rain garden (RG)) modules of themodel and the effect of the SUDS scenarios on the CSOs using event-based and continuous simulations. The Nash–Sutcliffe efficiency (NSE) along with flow duration curves (FDCs) has been used for evaluating the model performance. Event-based evaluations revealed the superior performance of the RG in reducing CSOs for larger precipitation events, while GRs were proven to have beneficial outcomes during smaller events. The study illustrated another way of assessing the continuous simulations by employing the FDCs. The FDCswere assessed against a discharge threshold at the outlet (which authorities can set as design criteria) of the catchment in terms of the extent, each scenario reduced occurrence and duration of outflow that invokes flow in the overflow pipe.

中文翻译：

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评估四种 SUDS 情景对挪威奥斯陆合流下水道溢流的影响：评估迈克城市模型的低影响开发模块

铺砌的表面、降水强度增加以及下水道系统的容量有限，导致合流下水道溢流 (CSO) 的风险更高。可持续排水系统 (SUDS) 提供了一种通过在当地管理雨水来减轻 CSO 的替代方法。基于有效减少不渗透面积的概念开发的七个 SUDS 情景已使用 Mike Urban 模型在 Grefsen 流域实施。本研究评估了模型的两个 SUDS 控制（即绿色屋顶 (GR) 和雨水花园 (RG)）模块的水文性能，以及使用基于事件和连续模拟的 SUDS 场景对 CSO 的影响。纳什-萨特克利夫效率 (NSE) 和流动持续时间曲线 (FDC) 已用于评估模型性能。基于事件的评估揭示了 RG 在减少较大降水事件的 CSO 方面的卓越性能，而 GR 在较小的事件中被证明具有有益的结果。该研究说明了使用 FDC 评估连续模拟的另一种方法。根据流域出口处的排放阈值（当局可以将其设置为设计标准）评估 FDCs 的范围，每种情况都减少了引发溢流管流量的流出的发生和持续时间。