Actually being from New England springs are not that uncommon. Also there is a lot of small streamlets and what not. I have no idea how hard it would be to create something to cause these (small streams and brooks) to be added to the math on non-specific tiles. There is a brook behind the house I grew up in that doesn’t go above you knees except in a few rare spots. It’s rocky as heck, as streams and rivers tend to be in New Hampshire.