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

据估计，2007年发生在英国的洪水造成了32亿英镑的经济损失，并导致13人死亡。据预测，由于气候变化、城市化和污水处理基础设施恶化的影响，洪水事件的频率和规模将会增加。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水事件。为了减轻这些影响，已经开发了城市洪水的水力模型，该模型描述了下水道系统的流量，城市集水区的陆上流量以及这些系统之间的流量交换，以便确定那些最容易发生洪水的地区。地方当局和水务公司使用这些模型来确定需要进行防洪工作的地区，例如优先投资改善排水基础设施、采取措施减少暴雨径流和提高居民的认识。然而，由于在洪水事件期间难以获得可靠的数据，因此这些模型的准确性本身就难以验证，例如，无法确保在洪水事件发生时准确预测模型的流道和流速。同样，但更为复杂的是，目前还不可能量化洪水事件中潜在危险的粪便污染物从下水道网络流向居民区的情况，因此也无法评估洪水对健康的风险。先前对洪水的采样表明，这种健康风险可能很大。相互作用点（如人孔）的行为对污水和地表之间的流动和污染的转移至关重要，但由于流动的复杂性，这种界面的水力行为特别难以量化。该方案旨在更好地理解谢菲尔德大学独特的比例模型设施内的这些互动过程，该设施将地下下水道系统的流动与集水区上的浅水表面流动结合起来，并通过一些人孔连接起来。研究的总体目标是改进城市洪水模型的验证过程，提供详细的测量和对相互作用点的水力特性的更准确的理解，量化地表水流路径，并提高对地表水流中下水道系统污染物扩散的建模能力。其结果将是大大提高城市洪水流量的建模能力，并大大提高对城市地区洪水风险的了解。这将通过使用谢菲尔德的设施进行详细的实验测试计划来实现，并结合最先进的建模工作来校准、改进和验证城市洪水模型。该方案得到了英国领先的城市洪水模型开发商（Innovyze, Microdrainage）以及顾问、水务公司和地方当局的支持和参与。这种伙伴关系将确保将研究结果纳入最新的建模方法，并用于改善英国的洪水风险评估。除了推进预测洪水范围和深度的现有模型外，将模型扩展到预测大规模运输也被认为是重要和雄心勃勃的，这将使洪水的质量和潜在的健康影响得到更好的确定。此外，为了进一步发展这些方面，扩展所建议的工作，包括表征洪水条件下沉积物从下水道到地表流动的特征，也具有重要价值。这将具有科学和实用价值，因为对健康构成重大威胁的污染物往往附着在下水道沉积物上。因此，该部门同意提供奖学金，利用该设施研究沉积物的运输，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.