I suspect it's like sexuality in the US forces "don't ask, don't tell"!
I left a rusty old anchor and chain in Vliho. But if you want to make
something big out of concrete you're going to attract unwelcome attention.
you proably need to ask the port police but I wouldn`t bother they wont be interested --- just do it anyway but as the other poster said don`t make it too obvious
If you feel the need to ask permission, believe it or not, the person to ask is the local mayor! You would be surprised at the powers they have, a drink or two works wonders.
As others have said however, it is not worth bothering, just do it! There are no do gooders or tree huggers out here, everyone does as they please and long may it be so.