Imagining an Unimaginable Amount of Rain



Poetry has been defined as the effort to express the inexpressible. In the context of the flooding caused by Hurricane Harvey, I think that much the same can be said for many disciplines, ranging from statistics to engineering.

Consider the following numbers:

Estimated volume of rainwater from Harvey that has fallen on the 18 most affected coastal counties of eastern Texas, in which 7 million of the state’s nearly 28 million residents live: 9 trillion gallons.

Estimated volume of rainwater from Harvey that has fallen on all of Texas: 15 trillion gallons.

Estimated volume of rainwater from Harvey that has fallen on all locations as of midday Monday, August 28: 19 trillion gallons.

Expected total volume of rainwater from Harvey on all of Texas: 21 trillion gallons.


Writing for the Washington Post, Matthew Cappucci has attempted to put into perspective just how much water has fallen on the most affected counties along the coast in eastern Texas:

The 9 trillion gallons of water dispensed so far is enough to fill the entire Great Salt Lake in Salt Lake City—twice!

It would take nine days straight for the Mississippi River to drain into Houston and equal the amount of water already there.

If we averaged this amount of water spread equally over the lower 48 states, that’s the equivalent of about 0.17 inches of rain—roughly the height of three pennies stacked atop each other—occupying every square inch of the contiguous United States. Imagine one downpour large enough to cover the entire country!

This amount of water could fill 2.3 percent of the volume of the mountain range containing Mount Everest in Nepal and is enough to occupy 33,906 Empire State Buildings, from basement to penthouse.

Capucci’s article is accompanied by a graphic that attempts to provide a visual image of the 2 mile wide and tall cube of water that 9 trillion gallons of water would constitute.

Cappucci’s article is available at:


By the time that Harvey moves away from the coastline of Texas, most of the directly affected areas will have received between 20 and 30 inches of rain.

In the Houston area, a storm producing 20 to 30 inches of rain is considered a once-in-  100-years event.

Over the last 25 years, however, Houston has had six such storms.

In the last ten years, Houston has experienced two storms conventionally categorized as once-in-500-years events.

Some locations around Houston will total between 40 and 50 inches of rainfall from Harvey. A storm producing 60 inches of rain is conventionally considered a once-in-a- million-years event.


The New York Times has produced the following video showing locations in Houston before and after the flooding being produced by Harvey:

Likewise, The Atlantic has compiled the following collection of photos of the flooding:


Lastly, an article from CNN Wire posted on the website of KTLA in Los Angeles includes the following very decidedly un-reassuring statistics on flood insurance:

Figures from the National Flood Insurance Program show that only 15% of homes in Harris County, which includes Houston, have flood insurance, while only 20% of homes in Nueces County, where the coastal city of Corpus Christie is located, are covered. . . .

“The National Flood Insurance Program’s exposure to major floods is on the rise, as evidenced by Hurricanes Katrina and Sandy,” the program director Roy Wright said earlier this year in a blog post. “These events generated claims of approximately $24.6 billion, leaving the NFIP $23 billion in debt to the U.S. Treasury.”

Bills have been introduced in Congress to close the funding gap by hiking premiums. But lawmakers worry about angering homeowners who are required to buy flood insurance, and that expensive policies would only discourage other people from buying them.


2 thoughts on “Imagining an Unimaginable Amount of Rain

  1. Pingback: Imagining an Unimaginable Amount of Rain | Ohio Higher Ed

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