Up to sixty-six percent of the world’s population inhabit the coastal fringe of the world’s landmass. It is no wonder then that in recent years much concern has accompanied the stories of accelerating sea-level rise and its potential physical and social consequences. With a best estimate of a 50cm rise in sea level by 2100, it is clear that this issue demands great attention. The consequences of such an increase are not well understood and it was not until recently that the investigation of long-term, large-scale coastal evolution was deemed necessary, contrary to the growing trend of small-scale research. Understanding how the coastal system has responded to environmental forcing over the long-term during the past is essential for predicting possible future scenarios. The coastal system can be modelled by a set of partial differential equations that represent the highly complex, non-linear relationships of those physical components comprising the coastal zone. They allow the environmental forcing to be varied (e.g. the wind and wave climate), so that the sensitivity between components in the coastal zone can be identified. These insights can be projected forward in time to provide a more complete understanding of coastal behaviour in the future.

Preliminary results using an explicit finite-difference scheme with periodic boundary conditions are shown below. A uniform beach with a transverse trough, Figure a), and an offshore wave height of 2m at an angle of 210o are used as input. Figure b) shows the wave-induced current velocities with a clear rip current and distinctive eddies. Horizontal mixing has shifted the rip in the longshore direction. Figure c) shows the water surface displacement (indicating zones of set-down and set-up) and Figure d) displays the shoaling wave height. Such current patterns are significant in the long-term evolution of the coast. They are forced by stochastic phenomena (e.g. waves and wind), so Monte Carlo techniques that simulate these features probabilistically are preferable. This work is in collaboration with the geography department.

Results from wave model

Slide Shows

Poster presented at the European Geophysical Society Conference, Nice, April 2001