Where is that high water mark again?

There are words on paper, specifying a high water mark - and then there is the reality of water flooding a beach, crashing over a promenade and into buildings, homes, garages and shops, lifting cement slabs as if they were grains of sand and folding up sheets of glass as if it were feathers.
 
 
The image was picked up from the blog on http://www.sailingcentral.net/