Paying attention to situations that can lead to undesirable gravity flow makes good design sense and negates potential callbacks.
In October of any given year, those cows can decide the grass really is greener on the other side of the fence. On a crisp fall morning, we may wake to the sound of a dozen or so Holsteins grazing on our lawn and feasting on the garden. Those girls simply found a hole in the fence and took advantage of it.