As environmental change is happening at an unprecedented pace, a reliable and proper urban drainage design is required to alleviate the negative effects of unexpected extreme rainfall events occurring due to the natural and anthropogenic variations such as climate change and urbanization. Since structure/configuration of a stormwater network plays an imperative role in the design and hydraulic behavior of the system, the goal of this paper is to elaborate upon the significance of possessing redundancy (e.g., alternative flow paths as in loops) under simultaneous hydraulic design in stormwater pipe networks. In this work, an innovative approach based on complex network properties is introduced to systematically and successively reduce the number of loops and, therefore, the level of redundancy, from a given grid-like (street) network. A methodology based on hydrodynamic modelling is utilized to find the optimal design costs for all created structures while satisfying a number of hydraulic design constraints. As a general implication, when structures are subject to extreme precipitation events, the overall capability of looped configurations for discharging runoff more efficiently is higher compared to more branched ones. The reason is due to prevailing (additional) storage volume in the system and existing more alternative water flow paths in looped structures, as opposed to the branched ones in which only unique pathways for discharging peak runoff exist. However, the question arises where to best introduce extra paths in the network? By systematically addressing this question with complex network analysis, the influence of downstream loops was identified to be more significant than that of upstream loops. Findings, additionally, indicated that possessing loop and introducing extra capacity without determining appropriate additional pipes positions in the system (flow direction) can even exacerbate the efficiency of water discharge. Considering a reasonable and cost-effective budget, it would, therefore, be worthwhile to install loop-tree-integrated stormwater collection systems with additional pipes at specific locations, especially downstream, to boost the hydraulic reliability and minimize the damage imposed by the surface flooding upon the metropolitan area.

中文翻译：

---

在水力设计下评估雨水结构的冗余

随着环境变化以前所未有的速度发生，需要可靠和适当的城市排水设计，以减轻由于气候变化和城市化等自然和人为变化而发生的意外极端降雨事件的负面影响。由于雨水管网的结构/配置在系统的设计和水力行为中起着至关重要的作用，本文的目标是详细说明在同步水力设计下拥有冗余（例如，回路中的替代流动路径）的重要性在雨水管网中。在这项工作中，引入了一种基于复杂网络属性的创新方法，以系统地、连续地减少给定网格状（街道）网络的循环数量，从而减少冗余级别。使用基于流体动力学建模的方法来为所有创建的结构找到最佳设计成本，同时满足许多水力设计约束。作为一般含义，当结构受到极端降水事件的影响时，与更多分支结构相比，环状结构更有效地排放径流的整体能力更高。原因是系统中占主导地位的（额外的）蓄水量和环形结构中存在更多替代的水流路径，而不是分支结构，其中只有独特的排放峰值径流路径存在。然而，问题是在网络中哪里最好地引入额外的路径？通过用复杂的网络分析系统地解决这个问题，下游回路的影响被确定为比上游回路的影响更显着。此外，调查结果表明，在不确定系统中适当的额外管道位置（流向）的情况下，拥有环路并引入额外容量甚至会加剧排水效率。考虑到合理且具有成本效益的预算，因此值得在特定位置（尤其是下游）安装带有附加管道的环路树集成雨水收集系统，以提高水力可靠性并最大限度地减少地表洪水造成的损害在大都市区。表明拥有环路并引入额外容量而不确定系统中适当的额外管道位置（流向）甚至会加剧排水效率。考虑到合理且具有成本效益的预算，因此值得在特定位置（尤其是下游）安装带有附加管道的环路树集成雨水收集系统，以提高水力可靠性并最大限度地减少地表洪水造成的损害在大都市区。表明拥有环路并引入额外容量而不确定系统中适当的额外管道位置（流向）甚至会加剧排水效率。考虑到合理且具有成本效益的预算，因此值得在特定位置（尤其是下游）安装带有附加管道的环路树集成雨水收集系统，以提高水力可靠性并最大限度地减少地表洪水造成的损害在大都市区。