Harvey Is Already the Worst Flood-Producing Storm in U.S. History

Not to lean too heavily on a cliché, but that whole "doing things big in Texas" clearly applies to Tropical Storm Harvey. Anyone with a pair of working eyes knows this is a horrible, tragic situation that won't be over for some time as recovery will likely continue for months. But just how historic is this massive natural disaster?

As so many of us have done throughout the storm, we have leaned on resources like the National Weather Service and the local weather site Space City Weather for information, and this is no different. The numbers are, quite frankly, astonishing.

Eric Berger at Space City Weather posted about this very topic on Monday afternoon. Since that time, portions of the area have added still more inches of rain. Climatologists will be reviewing data for perhaps years to fully understand the scope of this disaster, but here are a few things we know.

The entire Houston region, which encompasses multiple counties and thousands of square miles, averaged well over 20 inches of rainfall. Let that sink in for a moment. Twenty inches of rain over three days as an average total. Many parts of the region are over 30 and we are learning Tuesday morning that areas just south and east of downtown (South Houston, Friendswood, Pasadena) are now officially over 40 inches of rain. At this point, it appears almost certain a few spots will top 50 inches of rain.

A woman is transported to the George R. Brown Convention Center to seek shelter from Tropical Storm Harvey.
A woman is transported to the George R. Brown Convention Center to seek shelter from Tropical Storm Harvey.
Photo by Doogie Roux

To put that into context, the city of Houston averages just under 50 inches of rain per year. Some areas will have received their entire year's worth of precipitation in less than a week.

It is even more difficult to comprehend for those of us who lived through 2001's Tropical Storm Allison and thought nothing like that could happen again in our lifetime. Most experts classified Allison as a 500-year storm, which meant it had a 0.5 percent chance of happening in a given year. Reports are now coming out that Tropical Storm Harvey will be classified as a 1,000-year storm. Those are astronomical odds for both, and we've faced both in the span of less than 20 years.

In Allison, only a couple of small areas east and northeast of the city experienced rainfall totals eclipsing 30 inches. Most of the region got between ten and 20 inches. Given those numbers, Allison pales in comparison to Harvey and rain is still falling in areas, particularly east and south of Houston.

There will be weeks and weeks of data compiling before we know the actual, official numbers, but it is clear that Harvey is one of the most significant natural disasters in the history of the United States and the worst flooding event in American recording history.

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