Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology, SE-97187, Luleå, Sweden.
Department of Civil and Environmental Engineering, Norwegian University of Science and Technology, NO-7491, Trondheim, Norway.
J Environ Manage. 2021 Mar 15;282:111911. doi: 10.1016/j.jenvman.2020.111911. Epub 2021 Jan 12.
Gully pots actively trap sediments transported by urban runoff to prevent in-pipe blockages and surface flooding. However, due to poor maintenance (resulting in sediment build-up) and increasingly extreme wet weather events, the scour of previously-deposited sediments from gully pots is identified as a potential contributor to EU Water Framework Directive failure. While basal sediment scour deterministic models have been developed and validated using laboratory and field gully pot data sets, the ability of these models to predict behaviour at sites other than those for which they were established has not been addressed. Nor has the impact of future rainfall predictions on the role of gully pots as sediment sources been systematically examined. As a contribution to addressing these knowledge gaps, the performance of two gully pot basal sediment scour models of distinct complexity levels are evaluated under current and future rainfall conditions. The output from Model One suggests that the scour-induced total suspended solids in gully pot discharge can be kept well below 25 mg/L if the gully pot fullness level is maintained at under 60%. Results identify the opportunity to incorporate the actual/targeted ecological status of recipients in scheduling gully pot maintenance operations and that proactive gully pots maintenance will reduce the impacts of increased rainfall intensity/duration on the magnitude of sediment scour. Results from Model Two suggest that fine sediments are particularly susceptible to in-pot scour. For example, sediment with a specific gravity of 1.1 and diameter of >63 μm accounts for 50% of scour-induced total suspended solids in gully pot discharge. The effluent suspended solids concentrations predicted by the two models differ by up to two orders of magnitude. However, without further empirical field data pertaining to their respective competences/applications, neither model could be discounted at this stage. For example, the use of Model One is more appropriate in the establishment of gully pot maintenance schedules, with Model Two more suited to the dimensioning of gully pots based on performance requirements. This application, however, relies on the development and adoption of a more stringent regulation on gully pots discharge.
雨水口积极截留城市径流输送的泥沙，以防止管道堵塞和地表洪水。然而，由于维护不善（导致泥沙淤积）和日益极端的潮湿天气事件，从雨水口冲刷先前沉积的泥沙被认为是欧盟水框架指令失败的一个潜在因素。虽然已经开发和验证了基于确定性的底泥冲刷模型，这些模型使用了实验室和野外雨水口数据集，但这些模型预测除了建立模型的地点以外的其他地点的行为的能力尚未得到解决。也没有系统地研究未来降雨预测对雨水口作为泥沙源的作用的影响。作为解决这些知识空白的贡献，评估了两种具有不同复杂程度的雨水口底泥冲刷模型在当前和未来降雨条件下的性能。模型一的输出表明，如果将雨水口的满度保持在 60%以下，则可以将雨水口排放中的冲刷引起的总悬浮固体（TSS）保持在 25mg/L 以下。结果确定了在安排雨水口维护作业时将接收者的实际/目标生态状况纳入其中的机会，并且主动的雨水口维护将减少增加的降雨强度/持续时间对泥沙冲刷规模的影响。模型二的结果表明，细泥沙特别容易受到雨水口内的冲刷。例如，比重为 1.1 且直径大于 63μm 的泥沙占雨水口排放中冲刷引起的总悬浮固体的 50%。两个模型预测的出水悬浮固体浓度相差两个数量级。然而，在没有进一步关于各自能力/应用的经验现场数据的情况下，现阶段不能排除任何一个模型。例如，模型一更适合于建立雨水口维护计划，而模型二更适合于根据性能要求对雨水口进行尺寸设计。然而，这种应用依赖于制定和采用更严格的雨水口排放规定。
