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Harvey will make history books for nation's wettest storm

Give or take a few trillion gallons, Mother Nature dumped Lake Tahoe on Texas and Louisiana, making Hurricane Harvey not just a part of Houston's history, but modern storm history.

"This is certainly the most extreme precipitation event on record to affect any major city in the United States," said Jeff Masters, founder of Weather Underground.

Based on assessments by the National Weather Service and analyses by various meteorologists, Harvey rained down more water on a metro area than any storm in U.S. history. The estimated 34 trillion gallons of rainfall across East Texas and western Louisiana is about the same as Tropical Storm Allison in 2001, 2015's Memorial Day floods and last year's Tax Day floods - combined.

"The amount of water that fell was unprecedented," said Shane Hubbard, an associate researcher at the Space Science and Engineering Center at the University of Wisconsin-Madison.

Based on Hubbard's analysis and Weather Underground statistics, the storm's scope was enormous. Among the findings:

The record 51.88 inch recording at Cedar Bayou, east of Houston, is the continental U.S. rainfall record, surpassing a mark set during Tropical Storm Amelia in 1978.

The national record for a three-day rain total in a metro area is Hobby Airport Aug. 26-28, with 32.47 inches. Bush Intercontinental is third, over the same days, with 28.44 inches. The National Weather Service's official rain gauges are at the airports.

The area that received, on average, more than 40 inches of rain is slightly larger than the land mass of Puerto Rico.

The extent of significant rain is something officials are just starting to address, Hubbard said.

"Texas is a big place," he said. "Sometimes the sheer size gets lost."

According to his analysis, between Aug. 23 and Aug. 30 an area of nearly 29,000 square miles received 20 inches or more of rain. That is larger than 10 U.S. states.

Hubbard noted the area hit by heavy rains is larger than West Virginia, Delaware and Rhode Island combined.

Using weather monitors, Hubbard mapped where rain was most and least concentrated as storms pounded the area. Though some specific spots received more or less rain, Hubbard's data showed a concentrated 28 inches of rainfall or more from Rosenberg to east of Beaumont.

Central, coastal areas where the rains lingered received the most, with many spots receiving 50 or more inches, including a huge swell that deluged Dayton in Liberty County.

On the fringes, Austin, Nacogdoches and Corpus Christi received less than 10 inches. Some spots much closer to the heart of the storm also were spared, with Galveston seeing relatively little rain, as officials feared the potential for a massive storm surge that never appeared.

Reservoirs taxed

Houston's east side was walloped more than its west, though western neighborhoods saw some of the worst of the flooding as bayous swelled to overflowing, as Addicks and Barker reservoirs kept a lot of the waters back - sparing downtown Houston and the Texas Medical Center further flooding, but sending water into suburban homes behind the berms.

Harvey's historic rain totals are unlikely to surprise residents of Harris, Fort Bend and Liberty counties - many of whom watched rains keep falling and creeks and bayous keep rising in ways they had never seen.

"I've lived here all my life, and I'd never seen it so bad," said Chuck Melville, 79, who lives near Memorial Park. "My father lived here all his life, and he probably didn't see it so bad."

What might make Harvey so significant is the sheer mass, as Hubbard demonstrated. Other storms left more people in the area without power. Harvey's 70 fatalities - while notable - are a small fraction of the 6,000 to 12,000 believed killed during the storm of 1900 that flattened Galveston.

Yet it will certainly join Amelia, Camille, Allison and Ike as names associated with life in Houston. Storms like those simply aren't judged by the meteorological oddity, said Monica Perales, director of the Center for Public History at the University of Houston and an associate history professor.

"If we only look at total inches of rain or total lives lost, we lose what this storm meant in this particular time," Perales said.

Oral history in the making

Regardless of how much rain exactly their neighborhood got, she said Harvey's history will likely be captured in how residents recall the rains, the actions of others and their own challenges.

"Everybody has a story to tell - and in events like this - that is especially notable and the power of those stories is it gives us the texture of history," Perales said.

Though she was not in Houston for Allison, Perales noted the tales about it have connected her to the city. Harvey likely will fall into that line, she said, as a turning point and reference point of what the Houston area has endured.

"We have to understand these storms in relation to one another," she said. "I think the danger is in forgetting."