Morphological models for flood risk management in UK estuaries

Estuaries continually adapt to natural morphological (post-Holocene) adjustments, and past and present ‘interventions’. Moreover, Global Climate Change (GCC) could extensively affect mean sea levels, storminess, river flows and sediment supply. Such impacts have considerable socio-economic importance, and we need to be able to predict changes over several decades. ‘Development of Estuary Morphological Models’ (a project in the Estuaries Research Programme – UK Department for Environment, Food and Rural Affairs/ Environment Agency) produced a suite of modelling tools and algorithms for assisting in flood risk assessments. It consists of ‘top-down’ approaches (e.g., accommodation space, trend analysis, regime relationships) and ‘bottom-up’ process-based models (hydrodynamics with improved sediment transport, using Lidar bathymetry measurements). These are combined to form ‘hybrid’ morphological models. The models are used for examining influences of likely changes on habitats and flood defences. Findings in several major estuaries (Dee, Mersey, Ribble, Thames, Blackwater, Humber, Southampton Water and Tamar) were compared with a recently updated national database of observations. We can now quantify the capabilities of the different models to predict morphology evolution in the selected estuaries, their sources of uncertainty and sensitivity to GCC and interventions. Sediment and dynamics modules developed here will contribute to a future Estuary Management System