There's dialect, and there's accent, and there's spelling conventions, and they aren't the same thing. Whether you write "de ribber am" or "the river am" the same words are being used, and the same dialect, and people from that end of the country will pronounce it the same way.

I think there's a lot to be said for keeping to the common spelling conventions generally, rather than trying to indicate accents by adjusting the way shared words are spelt. Which isn't the same as trying to iron out dialect expressions and ways of using the words.