Numerical modelling of river and floodplain responses to environmental change

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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?