An integrated approach to modelling floodplain hydraulics, hydrology and nitrate chemistry
Price, David A.
PublisherUniversity of Bristol
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As part of the effort to satisfy the ever increasing demand for a greater understanding of fluvial, hydrological, chemical, sedimentological and geomorphological processes operating on the floodplain, mathematical simulation models have come to play a significant role in the understanding, prediction and management of the floodplain environment. Underlying the accurate numerical representation of hydraulically driven processes is the provision of a suitable floodplain hydrology model which accounts for the interaction between surface hydraulics and subsurface hydrology. Such a numerical representation is currently not available at the spatial and temporal resolution required. It is the aim of this thesis to develop a novel conceptual approach to modelling floodplain hydrology in which the fundamental need to consider the interaction between surface and subsurface flow is the floodplain environment is addressed. This is achieved through the interactive coupling of a one-dimensional finite difference infiltration model with the state-of-the-art two-dimensional physically based finite element hydraulic model, TELEMAC2D. The coupled model provides an unparalleled spatial and temporal representation of surface and subsurface flow processes within the floodplain environment. The utility of this integrated approach is explored through an application of the model to two areas of contemporary floodplain research. In the first of these the model is run to assess the impact of infiltration on flood flow prediction for an llkm reach of the River Culm, UK, over a range of flood and soil conditions. In the second the model is run to investigate the nitrate buffering potential of floodplain riparian soils during flooding. For this investigation a model accounting for nitrate transport and denitrification is developed within the existing integrated hydraulic-infiltration model structure. An evaluation of the results from both of these investigations supports the need for a new approach to modelling fluvially driven floodplain processes which accounts for the spatially interactive nature of floodplain hydrology.