He said deluges on par with the one that hit Lenore Court in 2004 flow down the Dead Run every decade or two, according to a stream gauge in Leakin Park, near where the stream converges with the Gwynns Falls, which empties into the Patapsco River’s Middle Branch between Wheelabrator’s Baltimore trash incinerator and Interstate 95. But the tables hydrologists use to compare floods suggest that 5 inches of rain should fall in one spot within two hours only once every 300 or 400 years.