Numerical modelling of river and floodplain responses to environmental change

世界上许多大型河流都受到一系列自然和人为干扰的威胁，包括气候变化、水坝建设、采矿、农业集约化、城市化、污染和过度抽取水资源。这些现象引起河流水流和泥沙的变化，进而引起河流的不稳定性、洪水输送能力和生态功能的变化，数值模型是预测河流在未来环境变化和人类活动影响下演变的重要工具。然而，尽管它们在这方面的重要性，大多数现有的数值模型不能代表控制河流演变的关键过程。关键缺失过程包括植被对水流和泥沙输移过程、河岸侵蚀和洪泛区发育的影响。此外，现有的河流演变模型往往把植被视为必须指定的东西（作为模型输入条件），而不是作为河岸和洪泛区景观的一个新兴特征，这是建立的产品，本研究将开发在河流和河漫滩的形态动力学模型中代表植被和植被效应的新方法进化将利用现有的实地、实验室和遥感数据集，并借鉴其他学科（如气候科学）中使用的动态植被模型所采用的方法，开发这些模型。新模型将在一系列环境设置中应用和评估河流，这些环境设置具有对比鲜明的植被类型，时间跨度为数十年至数百年，以证明模拟这些不同环境中各种河流风格的可行性。在对新模型进行评估之后，它们将被用来回答与植被在河流环境中的作用和意义有关的一系列关键问题。这些问题将包括：（1）植被和植被反馈在控制河流对人类活动的响应方面的作用是什么（例如，例如水坝建设）; (2)对比鲜明的河流景观对未来气候变化的敏感性如何？植被在控制这种敏感性方面起什么作用？(3)在河流演变模型中，植被影响的最低复杂性要求是什么？植被影响的忽略对数值模型的准确性和灵敏度有何影响？

Many of the worlds large rivers are under threat from a range of natural and anthropogenic disturbances, including climate change, dam construction, mining, agricultural intensification, urbanisation, pollution and over-abstraction of water resources. These phenomena drive changes in river flow regimes and sediment loads, which in turn can promote river instability and changes in flood conveyance capacity and ecological functioning.Numerical models are essential tools for predicting the evolution of rivers in the face of future environmental change and human activities. However, despite their importance in this regard, most existing numerical models fail to represent key processes that control river evolution. Key missing processes include the effects of vegetation on flow and sediment transport process, bank erosion and floodplain development. Moreover, existing models of river evolution tend to treat vegetation as something that must be specified (as a model input condition) rather than as an emergent characteristic of the riparian and floodplain landscape that is a product of the establishment, growth and mortality of a range competing vegetation types.This studentship will develop new methods of representing vegetation and vegetation effects within morphodynamic models of river and floodplain evolution. The models will be developed using existing field, laboratory and remote sensing datasets, and by drawing on approaches used in dynamic vegetation models used in other disciplines (e.g. climate science). The new models will be applied and evaluated for rivers across a range of environmental settings with contrasting vegetation types, over time periods of decades to centuries, in order to demonstrate the feasibility of simulating the wide range of river styles found in these different environments. Having evaluated the new models, they will be used to answer a set of key questions relating to the role and significance of vegetation in riverine environments. These questions will include: (1) What is the role of vegetation and vegetation feedbacks as controls on river responses to anthropogenic activities (e.g., such as dam construction)?; (2) How sensitive are contrasting riverine landscapes to future climate change, and what role does vegetation play in controlling this sensitivity?; (3) What is the minimal level of complexity required to represent the effects of vegetation in models of river evolution, and how does the neglect of vegetation effects impact on the accuracy and sensitivity of numerical models?