Understanding and modelling surface-subsurface flow interactions in urban areas during floods

城市地区的洪水风险管理已成为国家政府和地方当局的一个关键问题，因为它的政治和经济影响，以及由于气候变化和城市密度的增加而日益紧迫。虽然使用二维水动力模型的城市洪水分析现在能够对地表洪水风险进行现实的评估，但越来越明显的是，由于许多原因，地下域也很重要，应该在这些分析中考虑。基于地下水渗透（如洼地或绿地）的洪水风险管理的绿色基础设施（GI）正日益得到推广，但人们对其性能和对城市地下水位的影响知之甚少，并可能产生重大后果。这些后果可能是积极的，但更高的地下水位和不受控制的地表水渗透也可能破坏水管网络、地下室和地下运输网络。因此，更好地表征决定地表水-地下水相互作用的入渗水文过程和土壤含水量，是分析和设计最佳洪水风险防范措施和验证洪水衰减特征有效性的关键。因此，本项目旨在建立一个基于现代数值技术的地表-地下全耦合模型，以解决现有解决方案的主要问题，并将该模型应用于可能的气候情景，考虑土壤湿度的变化和GI或其他洪水风险预防措施的存在。在编程和数学技能和经验方面的难度很高，要求很高，但是，完成这个项目将产生重大影响。它将在洪水影响通常更严重的城市地区产生更准确和可靠的洪水模型。此外，通过使用明确模拟非饱和流动过程的模型，将有可能评估GI等洪水风险缓解特征的有效性。

Management of flood risk in urban areas has become a key issue for national governments and local authorities due to its political and economic implications and increasing urgency due to climate change and urban densification. While urban flood analysis using 2D hydrodynamic models now enables realistic assessment of surface flood risk, it is becoming increasingly obvious that the sub-surface domain is also important for a number of reasons and should be accounted in these analyses. Green Infrastructure (GI) for flood risk management based on infiltration to the groundwater (e.g. swales or green space) is increasingly promoted, but its performance and impact on the urban water table is poorly understood and can have major consequences. These consequences may be positive, but higher water tables and uncontrolled infiltration of surface waters can also damage water pipe networks, basements and underground transport networks. Hence, better representation of the hydrological processes of infiltration and soil moisture content which determine the surface-groundwater interactions, is key to analysing and designing the best flood risk prevention measures and verifying the effectiveness of flood attenuation features. Therefore, the project aims to develop a fully coupled surface-subsurface model based on modern numerical techniques in order to address the main issues of the existing solutions, and apply the model under possible climatic scenarios, considering changes in soil moisture and the presence of GI or other flood risk prevention measures.The difficulty in terms of programming and mathematical skills and experience is high and very demanding, however, accomplishment of this project will have a significant impact. It will produce more accurate and reliable flood models in urban areas where the effects of flooding are generally more severe. Furthermore, it will be possible to assess the effectiveness of flood risk mitigation features such as GI by using a model that simulates the unsaturated flow process explicitly.