End of the line!

Day off today. Had a few too many sherries last night so went for a walk along the promenade at Cramond to blow the cobwebs away..........My god it worked...it was freezing!!!!! Came across this while walking on the beach. Its the end of the line for a little stream which originates in the woods somewhere.
Also noticed that all the trees in that area are numbered!! I had never come across that before cane anybody tell me why???