Hurricane Harvey Is Testing Our Ability to Communicate Natural Disaster Risks

How do scientists drive home a threat that has no precedent?

Since slamming into the Texas coast as a Category 4 hurricane late Friday, Harvey has dumped at least 9 trillion gallons of rain across the state — enough to fill Utah’s Great Salt Lake twice.

And with Houston already inundated, the rain continues to fall.  One meteorologist estimates that by the time the storm subsides it will have dropped a mind-boggling 25 trillion gallons of water across the state.

Certain locations along the Gulf of Mexico are expected to see as much rain in a few short days as is typical in an entire year.  To accurately portray the staggering totals, the National Weather Service had to add new colors to its precipitation maps.

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#Harvey in perspective. So much rain has fallen, we've had to update the color charts on our graphics in order to effectively map it.
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Harvey has wreaked havoc along the Texas Gulf Coast, just as meteorologists warned it would.  But it has also proved somewhat of a communications nightmare. 

Marshall Shepherd, director of the Atmospheric Sciences Program at the University of Georgia and a former president of the American Meteorological Society, told HuffPost that the bottom line is this:  Harvey is an unprecedented storm system. 

“We’re kind of making this up as we go,” he said of meteorologists’ mapping and communication about the sheer magnitude of the event.  “We haven’t seen this type of rainfall over [such a short] amount of time.” 

Given precipitation totals through Monday and the forecast for the rest of the week, Shepherd said the situation in Texas “is shaping up to be [the] worst flood disaster in U.S. history.”

The previous benchmark for flooding in an American city was Tropical Storm Allison in 2001, which dumped 40 inches of rain on Houston in five days, killing nearly two dozen people and causing $5 billion in damage.  (The one-day U.S. record, 43 inches, hit rural Alvin, just south of Houston, during 1979′s Tropical Storm Claudette.)

Harvey delivered as much rain as Allison in roughly half the time — a statistic Shepherd described as “ridiculous.” 

For Shepherd and other experts, the extent of the disaster came as little if any surprise.  Early forecasts called for massive amounts of rain and “catastrophic and life-threatening flooding.” On Friday, the National Weather Service in Corpus Christi offered this stark warning: “Locations may be uninhabitable for weeks or months.”  And by Sunday morning, the NWS was cautioning that “all impacts are unknown & beyond anything experienced.”

As Harvey has shown, conveying to the public the deadly risks of such an unprecedented weather event is not easy.

Sarah Watson, a climate and flood risk communication consultant that does contract work for the National Oceanic and Atmospheric Administration, told HuffPost she sees the problem as cultural.  Many people associate tropical storms with wind and storm surges but not necessarily with heavy rain — which often proves to be the most destructive effect.  When a storm like Harvey is downgraded from a Category 4 hurricane to a tropical storm, for example, people are often quick to think the threat has subsided.

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