Saturday, September 17, 2011

Once in a Thousand Years

The rain train that barreled through central Maryland last week was a once in a thousand year rainfall. According to this story by Martin Weil in The Washington Post the deluge from Tropical Storm Lee “came down so fast for so long that it might have been a once-in-a-millennium event, according to a report from the National Weather Service.”

The September 8th rain storm dumped over six inches of rain over the area in a span of three hours.

“That, the weather service said Wednesday, “has less than a 0.1 per cent chance of occurring in any given year.” The extremely unlikely event, the service said, is “sometimes called a 1,000-year rainfall.”
Longtime residents of Ellicott City told me that this was the first time they can recall that the flooding was worse on upper Main Street than the lower portion of the street by the Patapsco River. This was precipitated by the overflow of the Tiber Branch channel that runs down the hill and under several buildings along the street. Right before the Ellicott Mills Brewing Company the river channel takes a ninety degree turn as it crosses under Main Street before continuing down to the river on the opposite side of the road. The volume of water in such short period of time was more than the channel could handle.
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