issThe value of different modelling approaches to investigate estuarine morphodynamics

Estuarine sediment transport is influenced by a large number of stochastic processes, at a variety of scales, driven by external factors and shaped by conditions within the coastal system. The prediction of sediment transport for the purpose of management and engineering is made uncertain by these complexities with explicit quantification difficult on management timescales. Numerical models, both complex and simplified, contain a lot of assumptions and parameter tuning is required. However models, in combination with historical assessment and field monitoring can be used to provide a best estimate of the rate of transport and causes of morphological change in estuarine environments. Due to the uncertainties of interactions at different spatial and temporal scales, this paper considers the value and necessity of a composite approach in order to understand estuarine morphodynamics. An assessment of sediment transport trends and morphodynamic changes in Courtmacsherry estuary, Ireland was produced by integrating data from a variety of sources - field monitoring, evaluation of geoindicators, a process-based model (Delft3D), a behaviour-orientated model (Asmita) and analysis of historical data. In this instance, the models were used as tools in identifying the important relationships between smaller-scale processes and in determining long-term trends, while recognising their inherent limitations and the importance of validation. It is shown that the process-based model simulates observations well on shorter time scales but the use of a behaviour-orientated model and historical data is necessary to determine if the correct long term behaviour is developed.