Lecture 1 - missing bits

There are a couple of things I missed out during the first lecture (always try and say too much in too little time). Most of the stuff missed out is in the first chapter of the course text, but I wanted to make sure that I emphasise one important concent: relaxation time.

Imagine you have a coastal feature that is out of equilibrium with the boundary conditions (waves, tides and sea level). It will try to adjust in an attempt to achieve equilibrium (through negative feedback). It will take time before an equilibrium is reached and this time is referred to as the relaxation time. The primary scale relationship tells us that the larger the feature the longer the relaxation time. And features such as long sections of cliffed coastlines and tidal basin may have relaxation times of 1000's or even 10,000's of years.

This means that many of such large coastal systems are currently still changing in response to the post-glacial sea-level rise: even though sea level has attained present-day level approximately 5,000 years ago, the coastline at large is still adjusting. This is why erosion of the Holderness coast (see map), for example, has nothing to do with current accelerated sea-level rise: the coast is still responding to the post-glacial sea-level rise. Many large coastal systems are still out of equilibrium due to the large relacxation times.