Experimental and numerical investigation of pluvial flood flows and pollutant transport at and between system interface points

据估计，2007年英国发生的洪灾造成了32亿英镑的经济损失，造成13人死亡。由于气候变化、城市化和废水基础设施恶化的影响，洪水事件的频率和规模预计将增加。仅在去年夏天，纽卡斯尔、曼彻斯特、贝尔法斯特和许多其他英国城镇就经历了严重的洪灾事件。为了减轻这些影响，已经开发了城市洪水水力模型，该模型描述了下水道系统中的水流、城市集水区中的陆上水流以及这些系统之间的流量交换，以确定哪些地区最有可能发生洪水。这些模型被地方当局和自来水公司用来确定洪灾缓解工作的地区，例如优先投资改善排水基础设施，采取措施减少暴雨径流，并提高居民的意识。然而，由于在洪水事件期间很难获得可靠的数据，这类模型的准确性本身就很难验证，例如，确保在洪水事件发生时准确地预测所建模的水流路径和速度是不可行的。同样，但更复杂的是，目前还不可能量化洪水事件中潜在危险粪便污染物从下水道网络向居民区的运输，从而评估洪水对健康的风险。此前对洪水的采样表明，这种健康风险可能是巨大的。相互作用点(例如检修孔)的行为对于这种流动和污水在下水道和地面之间的转移至关重要，但由于流动的复杂性质，这种交界处的水力行为尤其难以量化。这项提议试图在谢菲尔德大学一个独特的比例模型设施中更好地了解这些互动过程，该设施将地下下水道系统中的水流与汇水区上的浅水表面水流结合起来，通过多个检修孔连接起来。这项研究的总体目标是改进城市洪水模型的验证过程，提供详细的测量和更准确地了解相互作用点的水力特性，量化地表水流路径，并提高地表水流中污水系统污染物扩散的模拟能力。其结果将是对城市洪水流量的建模能力大大增强，并大大改善对城市地区洪水风险的了解。这将通过使用谢菲尔德设施的详细实验测试计划以及最先进的建模工作来实现，以校准、改进和验证城市洪水模型。该提案得到了英国城市洪水模型的领先开发商(Innovyze、MicroDepage)以及咨询公司、自来水公司和地方当局的支持和参与。这一伙伴关系将确保研究结果被纳入最新的建模方法，并被用于改善英国的洪水风险评估。除了推进现有预测洪水范围和深度的模型外，将模型扩展到预测集体运输被视为重要和雄心勃勃的，这将使更好地确定洪水对质量和潜在健康的影响。此外，为了进一步发展这些方面，扩大拟议的工作范围也具有重要价值，该工作包括描述洪水情况下泥沙从下水道向地表流动的特征。这将具有科学和实用价值，因为构成重大健康风险的污染物往往附着在下水道沉积物中。因此，该部门同意提供奖学金，利用该设施研究沉积物的输送，进一步扩大拟议工作的价值。

The 2007 flood events in the UK were estimated to have had an economic cost of £3.2billion and resulted in 13 deaths. The frequency and magnitude of flood events has been forecast to increase due to the impacts of climate change, urbanisation and the deterioration of wastewater infrastructure. In the last summer period alone Newcastle, Manchester, Belfast and many other UK towns and cities have experienced significant pluvial flooding events. To mitigate these effects urban flooding hydraulic models have been developed which characterise the flow in the sewer system, overland flow in the urban catchment, and the exchange of flow between these systems so as to identify those areas which are most at risk of flooding. Such models are used by local authorities and water companies to identify areas for flood mitigation work, such as prioritising investment to improve drainage infrastructure, taking measures to reduce storm water runoff and raising the awareness of residents. However the accuracy such models is inherently difficult to verify due to the difficultly of acquiring reliable data during flood events, e.g. it is not feasible to be sure that the modelled flow paths and velocities are accurately predicted at the time of the flood event. Similarly, but more complexly, it is not currently possible to quantify the transport of potentially dangerous faecal contaminants from the sewer networks to residential areas in flood events, and hence to assess the risk to health of flood waters. Previous sampling of flood waters has shown that this health risk may be significant. The behaviour of interaction points (e.g. manholes) is critical to the transfer of such flow and pollution between sewer and surface, but the hydraulic behaviour at such interfaces is especially difficult to quantify due to the complex nature of the flow. This proposal seeks to better understand these interactive processes within a unique scale model facility at the University of Sheffield that combines the flow in a below ground sewer system with the shallow water surface flows over the catchment, linked by a number of manholes. The overall aim of the research is to improve the verification process of urban flood models, to provide detailed measurements and a more accurate understanding of the hydraulic characteristics of interaction points, to quantify surface flow paths and to advance the modelling capability to the spread of pollutants from sewer systems within the surface flow. The outcome will be a significantly enhanced modelling capability for urban flood flows and a much improved understanding of flood risk in urban areas. This will be achieved by a detailed programme of experimental testing using the facility at Sheffield, coupled with state of the art modelling work to calibrate, improve and verify urban flood models. The proposal enjoys the support and engagement of leading developers of urban flood models in the UK (Innovyze, Microdrainage), as well as consultants, water companies and a local authority. This partnership will ensure that the research findings are incorporated into the latest modelling approaches and are utilised to improve flood risk evaluation in the UK.As well as advancing existing models that predict flood extent and depth, it is seen as important and ambitious to extend models to predict of mass transport, which will enable quality and potential health implications of flooding to be better established. In addition, to develop these aspects further, there is also significant value in extending the work proposed to include characterising the transport of sediments from sewers to surface flow in flood conditions. This would be of scientific and practical value as contaminants that pose a significant health risk are often attached to sewer sediments. The department has therefore agreed to provide scholarship which will use the facility to study the transport of sediments, further expanding the value of the proposed work.