I'll try to remember to snag a picture later, but from the box drain to the backyard (side of house) it's a pretty good slope then once it hits the back yard it kinda levels but then slopes for 50 or so more feet pretty good.

The drain here goes all the way back a few hundred feet and on the way is connected to another downspout and I am not sure how they did it and I don't even know if I want to look lol