Adaptive mesh simulation of different scale flood inundation

洪水灾害，包括沿海洪灾和河流泛滥，是对人类生命和财产的重大威胁。在英国，气候变化和日益增加的社会经济脆弱性意味着，除非当前的洪水管理政策和投资水平能够得到修改，否则21世纪洪水风险预计将显著增加。洪水风险管理研究联盟(FRMRC)由EPSRC和其他政府部门和机构资助，以提高对洪水原因的了解，并开发洪水风险管理工具。洪水模拟工具的开发和评估一直是该联盟的研究课题之一。这项建议扩展了FRMRC的工作，建议评估和改进洪水流动的计算机模型，该模型可以适应当地的地形和障碍物，即使在流动非常复杂的地方也能有效地生成准确的解决方案。这将意味着，第一次可以在不同的尺度(从小到非常大)范围内应用非常准确的模拟，包括大范围的洪水相互作用。该项目与FRMRC的研究目标一致，但具有创新性，因为这是首次将自适应模型应用于模拟真实世界的大规模洪水情景。该模型将利用现代数值技术，包括用于计算效率和精度的自适应网格方法、用于计算效率的局部时间步长方法、用于计算效率的简化扩散波方法和用于计算精度的全二维浅流计算方法。它将为不同尺度的洪水模拟提供一个强大、高效和准确的数值工具，应用范围广泛。特别是，该模型将允许模拟超大规模的洪水淹没(例如整个泰晤士河口地区)，同时还可以解决防洪堤上的局部水流的影响。由于滩地规模很大，地形地貌复杂，包括城市结构，这项任务目前已经超出了现有的大多数数值工具的范围。拟议的项目将在3年内完成，包括进一步开发现有的基于自适应四叉树网格的浅水水流模型，用于不同尺度的洪水模拟。该项目的头两年将侧重于进一步开发和使用计算机模型。与尺度效应、近似精度等有关的问题将得到妥善解决。通过与FRMRC推荐的现有洪水模拟计算机模型的比较，验证了该模型的有效性、准确性和稳健性。在过去的一年里，改进的计算机模型将应用于整个泰晤士河口地区由于不同重现期的极端潮汐条件，包括洪水波的大范围相互作用而产生的未来洪水淹没情景的预测，该项目的计算机模型可以用于工程师和研究人员在不同情况下预测洪水风险，为改进洪水风险评估提供可靠的依据。因此，本文的研究将对涉及洪水风险评估和管理的工程顾问和保险企业有直接的借鉴意义。环境署和地方当局将受益于这项工作产生的更大规模的洪水模拟和相关风险分析将为更好地管理和减轻洪水风险提供进一步的信息。这将反过来在减少洪灾风险和改善洪灾风险沟通方面惠及广大公众。

Flood disasters, including coastal flooding and river inundation are a major threat to human life and assets. In the UK, a combination of climate change and increasing socio-economic vulnerability mean that the risk of flooding is expected to increase significantly during the 21st century unless the current policies for flood management and investment levels can be modified.The Flood Risk Management Research Consortium (FRMRC) has been funded by EPSRC and other government departments and agencies to improve understanding of the cause of flooding and to develop tools for flood risk management. The development and assessment of flood simulation tools has been one of the consortium's research topics. This proposal extends the work in FRMRC by proposing to assess and improve a computer model of flood flows that can adapt to local topography and obstruction, efficiently generating accurate solution even where the flow is very complex. This will mean that, for the first time, very accurate simulation can be applied at a range of different scales (from small to very large), including broad scale interactions of flood flow. This proposed project is consistent with the FRMRC research aims, yet is original in that this is the first time the adaptive model will be applied to simulate large-scale real world flood scenarios. The model will take advantages of modern numerical techniques including adaptive mesh methodologies for efficiency and accuracy, a local time step approach for efficiency, a simplified diffusion wave method for efficiency, and fully 2D shallow flow solution for accuracy. It will result in a robust, efficient and accurate numerical tool for flood simulation at different scales for a wide range of applications. Particularly, the model will allow simulation of very large scale flood inundation (e.g. the whole Thames Estuary area) whilst also resolving the effect of local flows at flood defences. This task is currently beyond most of the existing numerical tools as the scale of the floodplain is very large and the topographic features are complicated, including urban structures.The proposed project, involving further developing an existing adaptive quadtree grid based shallow flow model for flood simulation in different scales by including some model numerical techniques, will be completed in 3 years. The first two years of the project will focus on further developing and accessing the computer model. Problems related to scale effects, accuracy of approximations, etc. will be properly addressed. The efficiency, accuracy and robustness of the model will be confirmed by comparing with existing computer models for flood simulation recommended by FRMRC. In the last year, the improved computer model will be applied to predict future flood inundation scenarios in the whole Thames Estuary area due to extreme tidal conditions with different return periods, including broad scale interaction of flooding waves.The computer model resulted from this project can be used by engineers and researchers to predict flood risk in different situations and provide a reliable basis for improved flood risk assessment. Therefore this research will directly benefit engineering consultants and insurance business involving assessment and management of flood risk. The Environment Agency and local authorities will benefit in that larger scale flood simulation and related risk analysis resulting from this work will provide further information for better flood risk management and alleviation. This will in turn benefit the general public in terms of flood risk reduction and improved communication of flood risk.