This was the site of one of the worst flash floods in recent history on this date in 1977.  It occurred in Jamestown, Pennsylvania, and it killed  84 people and caused $300 million in damages.  No flash flood has killed more people in the U. S.   Twelve inches of rain fell in ten hours,  and it was estimated that this kind of rain only falls in that area every 1000 years.

For more info:
http://www.history.com/this-day-in-history/second-great-flood-hits-johnstown
http://www.erh.noaa.gov/ctp/features/2012/Johnstown1977/
http://www.weather.com/blog/weather/8_13074.html