Are national maps drawn with reference to high/low or average tide levels? And has it been neccessary to redraw any maps yet because of global warming?
Depending on scale some Ordinance Survey maps contain this info for the UK, they also show the tidal reach on rivers near the coast. Here
(I don’t know how often the maps are updated but I’m guessing it would be too soon to see any changes directly attributable to global warming, Britain’s coatsline has been evolving forever with the demise of the coastal town Dunwich being one of the best documented.)