Designing for exceedance events consists in designing a continuous route for overland flow to deal with flows exceeding the sewer system’s capacity and to mitigate flooding risk. A review is carried out here on flood safety/hazard criteria, which generally establish thresholds for the water depth and flood velocity, or a relationship between them. The effects of the cross-section shape, roughness and slope of streets in meeting the criteria are evaluated based on equations, graphical results and one case study. An expedited method for the verification of safety criteria based solely on flow is presented, saving efforts in detailing models and increasing confidence in the results from simplified models. The method is valid for 0.1 m²/s 0.5 m²/s. The results showed that a street with a 1.8% slope, 75 m^1/3s⁻¹ and a rectangular cross-section complies with the threshold 0.3 m²/s for twice the flow of a street with the same width but with a conventional cross-section shape. The flow will be four times greater for a 15% street slope. The results also highlighted that the flood flows can vary significantly along the streets depending on the sewers’ roughness and the flow transfers between the major and minor systems, such that the effort detailing a street’s cross-section must be balanced with all of the other sources of uncertainty.

中文翻译：

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洪水街道上的人们安全设计：不确定性和横截面形状、粗糙度和坡度对危险标准的影响

超限事件设计包括为地表水流设计一条连续的路线，以处理超过下水道系统容量的水流并减轻洪水风险。这里对洪水安全/危害标准进行了审查，这些标准通常确定水深和洪水速度的阈值，或它们之间的关系。街道的横截面形状、粗糙度和坡度对满足标准的影响是根据方程、图形结果和一个案例研究来评估的。提出了一种仅基于流量来验证安全标准的快速方法，可节省详细模型的工作并增加对简化模型结果的信心。该方法对 0.1 m ² /s 0.5 m ^{2 有效}/秒。结果表明，坡度为 1.8%、75 m ^1/3 s ^{− 1}和矩形横截面的街道符合 0.3 m ² /s的阈值，适用于宽度相同但具有常规流量的街道流量的两倍。横截面形状。对于 15% 的街道坡度，流量将是其四倍。结果还强调，根据下水道的粗糙度以及主要和次要系统之间的流量转移，沿着街道的洪水流量可能会有很大差异，因此详细描述街道横截面的工作必须与所有其他来源相平衡的不确定性。