The liquid many Pittsburghers associate with March 17 is green beer. But there still are a few folks around who can remember St. Patrick's Day 1936, when the dark brown waters of creeks and rivers fast rose into the region's worst natural disaster.

Fed by extraordinary snow melt and rain, the ice-filled three rivers crested at the Point that March 18 at the highest mark since anyone has kept track: Just over 46 feet. (That's 15 feet, or more than a story, higher than the last big flood many of us experienced in September 2004.)

In 1936, the Allegheny and Monongahela rivers were converging near Smithfield Street. Downtown below that was under as much as 15 feet of water that filled all the first floors and basements. It was the same in low areas up and down the rivers, from Ambridge to Vandergrift, where thousands had to be rescued from their second stories.