History

The iCOASST project grew out of previous work by the Tyndall Centre's Coastal Simulator, which assessed how coastal changes physically affect a region and the impacts of flooding and erosion, and the joint Defra/EA Flood and Coastal Erosion Risk Management R&D programme, which funded the Estuaries Research Programme (ERP) that laid the groundwork for a lot of hybrid coastal morphology modelling ideas and project SC060074 on characterisation and prediction of large-scale, long-term change of coastal geomorphological behaviours.

Previous Research

The challenge posed by climate change requires a paradigm shift in our approach to coastal erosion and flood risk management. The cumulative effect of human intervention on coastlines has left them far from equilibrium under today’s conditions. Future changes in marine forcing due to climate change intensify the need to understand and predict processes of change in shoreline position and configuration at management (decadal to century) scales. This leads directly to the challenge of predicting landform behaviour at the meso-scale of 101 to 102 km and time horizons of 101 to 102 years . Presently, meso-scale evolution is poorly understood being situated between more detailed knowledge of microscale sediment transport processes, and of broader coastal evolution, informed by Quaternary to Holocene stratigraphy and by empirical analyses of past shoreline change.

Concepts of sediment mass conservation and sediment budgets are crucial to understand landform dynamics. Since the 1960s, the idea of the coastal sediment cell has proved invaluable as a basis for estimating sediment budgets (French 2004) and as a framework for coastal management. However, the concept has significant limitations, especially on more open coasts where boundaries are harder to identify. Moreover, the cell concept is ill-suited to representation of broad-scale linkages between estuarine, coastal and offshore systems or long-range suspended sediment pathways. There is thus a pressing need to formulate a conceptual model that better integrates open coasts with estuaries, incorporates sediment pathways for fine-grained as well as beach-grade material, and which considers sediment exchanges with the coastal shelf.  Such a model must be validated (wherever possible) with reference to sediment transport studies and/or physically-based modelling.

Various approaches have been used for predictive modelling of meso-scale coastal morphodynamics. Whilst ‘bottom-up’ process-based analyses, which couple hydrodynamic and sediment transport models are attractive in terms of their physical principles and widespread applicability, they work best for well-constrained problems with limited space- and time- horizons. Problems inherent to integrations over long time scales have encouraged experimentation with semi-empirical parameterizations to represent form-process linkages at a broader scale. This so-called ‘reduced complexity’ (RC) approach is commonplace in geomorphology but has been less widely applied to coastal landforms. An example is the SCAPE model, which demonstrates a broader range of emergent behaviours and responses to sea-level rise than are predicted by equilibrium 'top down' models such as the Bruun rule of shoreline erosion. Cellular or raster-based models, which are based on the concept of cellular automata, have also been applied to coastal landscape and ecosystem change, but with the exception of preliminary work by, have not been widely applied to problems with a strong geomorphological aspect. One model with considerable potential in this respect is SLAMM (Sea Level Affecting Marshes Model) which simulates intertidal shoreline modifications and habitat conversions in response to sea-level rise.

Despite the progress described above, we cannot yet predict the mesoscale evolution across the coastal forms and situations encountered in the UK (or worldwide). Improving this situation requires approaches that will bring together formalised knowledge of coastal systems with the quantified broad scale analysis that ‘bottom-up’ hydrodynamic and sediment transport models can provide, and with the systems insights from a new generation of reduced complexity models. This has the potential to deliver quantitative morphodymamic predictions, including uncertainties, that are relevant to coastal managers.