Surprising how that adds up, isn't it?! A couple weeks ago we had storm sit on us for 20 hours, dumping 7" on our .58 acre yarden, so by those calculations we had nearly 10,000 gallons of water. It's no wonder there were many flooded basements around. Not ours though, because it ran down our drive carrying lots of gravel and freshly sown grass seed out to the street. Ugg...
Better to shovel gravel than pump 300 gallons out of the basement like our neighbors!