Coastal and estuarine physical processes: looking back, looking forwards

Despite the continuing importance of good quality field data in estuarine and coastal settings, recent years have seen comparatively fewer field studies, replaced by an explosion in the use of numerical models to simulate the physical processes associated with transport by waves and currents, involving many things including the movement of solutes, solvents and floating particles or swimming organisms. The past few decades have seen vast progress in the development of many different models to simulate these physical processes, all of which have to some extent reduced the reliance on fieldwork as a primary means of collecting data and improving understanding of the processes involved. Many of these models are now in such common use by the scientific community that their routine application is no longer described in the scientific research literature. Some of the newer modelling approaches such as Machine Learning and Artificial Intelligence are also starting to see wider use to answer questions about coastal physical processes. The question remains as to the future direction of modelling efforts and the ambition of the modelling community to develop tools to inform the agenda for scientists and managers of coastal and estuarine environments. It seems likely that most of these efforts will be devoted to questions associated with climate change and rising sea levels, and of the transport of microplastics. In this chapter, we discuss some of the current achievements in modelling the physical processes that take place in estuaries and coasts and set out also some of the barriers to future progress. Though computing power is in many cases no longer an obstacle to modelling and prediction, there are still ways in which continued uncertainties plague the best efforts of modellers to capture the behaviours of particles and solutes, which may be governed by forces other than those strictly related to the flow of water. We also discuss the likely challenges in terms of pressing questions currently being asked about the coastal environment and how we manage it, especially in relation to sea level rise, the fate of microplastics, and increasing urbanisation of coastal zones. We finish by asking to what extent the current approaches used by modellers are appropriate for answering the main questions for the next few decades.