I think it’s Maryland where you are actually taxed on the rain runoff from your roof. They calculate sq/ft and tax you accordingly. One inch of rain on a 300sq/ft roof produces “X” amount of runoff into the sewers or some such idiocy.
Yes, you are correct, except that your driveway, parking area, and other impermeable surfaces are included along with the roof.
I live in Martinsville Indiana and they just last month stated this crap here. It will cost us about $100/year for our one acre lot in the industrial park for rain water. And this is for every square foot of land in the city limits, residential and commercial including your yard as well. We calculated how many millions of dollars this tax will cost people, and there is no announcement on where the money will officially go either other than "waste water treatment".