A new paradigm for urban flood design storms accounting for variability in space and time under climate change

城市洪水造成的破坏程度和严重程度是降雨强度和持续时间（在空间和时间上是可变的）及其与城市地表和地下（排水网络）复杂流道相互作用的产物。气候变化下的城市排水弹性设计目前因缺乏现实的设计方法而受阻。通常，在设计中使用基于点降雨测量的强度-持续时间-频率（IDF）曲线，这种使用具有标准时间和均匀空间剖面的单一事件被广泛认为是不现实的，因为大城市地区的单个风暴事件在关键属性上表现出很大的差异，它们的空间分布和顺序可能与城市中的关键路径和脆弱区域强烈相互作用。因此，这项博士研究的主要目标是利用高分辨率气候模型输出、先进的随机建模方法和CityCAT城市洪水建模系统来分析气候变化中的极端降水。该项目将开发新的风暴集合描述，用于具有不同特征的城市的多种水动力模拟。新方法将使用真实的城市以及合成网络来开发，以提供更广泛的情况来展示稳健的设计优化。由此产生的框架将广泛适用于水务公司、主要的地方洪水管理部门和咨询公司。在这项工作中，将使用高分辨率气候模型输出来创建一种方法，用于在气候变化下推导一系列城市的真实风暴事件。这些事件将被用于优化城市排水设计。这将通过创建一个框架来运行和分析来自完全耦合（地表和地表排水网络）的水动力模型CityCat的水动力模拟来实现。还探讨了可能的蓝绿干预措施。

The extent and severity of the damage caused by urban floods is a product of both the intensity and duration of the rainfall (variable in space and time) and its interaction with the complex flowpaths of a city, on the surface and below ground (drainage network). Resilient design of urban drainage under climate change is currently blocked by the lack of a realistic design storm methodology. Conventionally, Intensity-Duration-Frequency (IDF) curves based on point rainfall measurements are used in design and such use of single events with standard profiles in time and uniform in space is widely recognised to be unrealistic, as individual storm events in large urban areas show great variation in key properties, and their spatial distribution and sequencing can interact strongly with critical pathways and vulnerable areas in cities. The main objective of this proposed PhD research is therefore to analyse precipitation extremes in a changing climate using high resolution climate model outputs, advanced stochastic modelling methodologies and the CityCAT urban flood modelling system. This project will develop new ensemble descriptions of storms to be used in multiple hydrodynamic simulations of cities with different characteristics. The new methodology will be developed using real cities, as well as synthetic networks in order to provide a wider range of situations to demonstrate robust design optimisation. The resulting framework will be widely applicable and of interest to water utilities, lead local flood authorities and consultancies. In this work, high-resolution climate model outputs will be used in order to create a methodology for deriving realistic storm events for a range of cities under climate change. These events then are going to be used to optimize urban drainage design. This will be achieved by creating a framework to run and analyse hydrodynamic simulations from the fully coupled (surface and surface drainage network) hydrodynamic model CityCat. Possible blue-green interventions also be explored.