[flybouy]

"how would it go down, and only affect around the entrance area ?"

Water, like electricity, air, and a kid in college, will take the path of least resistance. A roof leak can drip feet away from it's entry point if it runs along the sheathing or rafter.. If water is flowing inside a wall gravity will pull it straight down until it encounters an obstruction. Then it would pool until it gets to a level where there's another path down. Think of those glass walled ant farms where they tunnel in different directions.