|Flood damage in Ellicott City, Maryland.|
As anyone who has seen the videos, the photos and the news reports, this was truly one of the scariest flash floods to affect an American city in recent years
TERRIFYING WATER, LUCKY BREAKS
Judging from the videos we've seen of the Ellicott City flood disaster, it's amazing only two people died. The charming, historic downtown was bustling with restaurant goers, shoppers, residents and such when the torrential thunderstorms arrived.
As extremely tragic as this flood was, some lucky breaks probably saved lives. Flash flood warnings from the National Weather Service were timely and strongly worded, giving people who heard them the urgency to get out of the way.
The 135 buildings affected by the flooding in downtown Ellicott were sturdily built, so none collapsed as hundreds of people fled to second floors. Even so, at least two buildings in Ellicott City are now on the verge of collapse because of the flood, but luckily held, sort of, during the flood.
A big lucky break is that the electricity stayed on in much of the flood zone during the disaster. That meant rescuers could see victims in the water and get them out of danger. It would have taken much longer to find them in the dark, light up the area where they were, and get them out.
The longer people would have been in the raging torrent, the more likely they would have died.
For people caught in buildings, the flood would have been even more terrifying had the lights gone out. The more scared people are, the more likely they are to do dumb or impulsive things. That could get you in trouble in a hurry during a flash flood.
People also might have unknowingly stepped out into raging water had there been no lights.
Rainfall rates in and around Ellicott City Friday evening were off the charts, notes the Washington Post's Capital Weather Gang. The Maryland city had 0.8 inches of rain in just five minutes. A little more than 3 inches in a half hour. 4.5 inches in an hour -- which, by the way, is about what would normally fall over the course of a month in Ellicott City.
With that rainfall rate, you can see why torrents formed so quickly.
The inevitable question comes next: Did global warming cause this?
|Another view of severe flash flood damage in |
downtown Ellicott City, Maryland.
The short answer: We don't know. The National Weather Service regarded this as a one in a thousand year event.
That means that in any given year, there's a one in one thousand chance such a big storm would hit the area. It doesn't mean that Ellicott City is safe for the next 1,000 years. It's all the role of the dice.
As the Capital Weather Gang explains, a combination of incredibly high humidity, converging air flow in Maryland and atmospheric instability unleashed the terrible flood. (By converging air, I mean winds in the atmosphere came from different directions and collided over that part of Maryland. When this happens, the air rises, and rising air can set off intense thunderstorms in this kind of air mass.)
I'm not sure if anyone will ever be able to say whether global warming caused this. The best we can do is say that scientists know the frequency of extreme rainfall events is increasing in many parts of the world, including most of the United States.
According to Grist:
"As the temperature of the atmosphere rises, it can hold more moisture, meaning the storms of the future will have more available to turn into torrential rains.
This trend is already visible across the United States, as well as in Maryland. Between 1958 and 2012, the heaviest 1 percent of all rainfall events rose 71 percent in the northeastern part of the country."
Given that, it follows that the Ellicott city disaster might have been influenced by climate change, but we'll probably never know for sure.
There might be another human dimension that might have made the disaster worse. . As Marshall Shepherd notes in Forbes. a lot of the country is urbanized now, covered with asphalt, concrete, streets, parking lots and the like.
Those surfaces are impervious, as opposed to fields and forests, which can absorb some of the excess water that comes with torrential downpours.
All that concrete means water will rush into gulleys and rivers much faster, worsening floods like the one that hit Ellicott City last Saturday.
Just remember, as the people of Ellicott City learned, that every flash flood warning should be taken seriously. As the name implies, these disasters sneak up to you on a moment's notice.