Hurricane Harvey was a Category 4 storm that hit Texas on August 25, 2017. It caused $125 billion in damage according to the National Hurricane Center. That’s more than any other natural disaster in U.S. history except Hurricane Katrina. Harvey dumped record levels of rain, causing extreme flooding.
At least 68 people died from the direct effects of the storm. Another 35 people died from related causes, such as car accidents.
The storm dumped 1 trillion gallons of rain on Houston in four days. At its peak on September 1, 2017, one-third of Houston was underwater. Flooding forced 32,000 people out of their homes and into shelters.
Harvey's impact was due to a combination of the storm's power, duration, and location.
When Harvey made landfall, its winds were 130 miles per hour. Its storm surge reached up to 10 feet above ground level. It also produced 52 tornadoes.
Harvey made landfall three times in six days. The storm lasted a record of 117 hours, stalling over the coast for four days. The Houston metro area is the nation’s fourth-largest city with 6.6 million residents.
The Facts on Hurricane Harvey's Damage
Over 300,000 structures and 500,000 cars were flooded. One year later, 8% of displaced people still couldn't return to their homes.
There were 61 drinking water facilities that were inoperable and 203 boil-water notices in effect. Another 40 wastewater treatment facilities were inoperable. Almost 150 gallons of sewage overflowed. There 266 hazardous materials spills. Around 13 million cubic yards of debris had to be removed.
Harvey's impact spread across the country as gas prices rose. Harvey forced 25% of oil and gas production to shut down in the region, affecting 5% of nationwide output. Approximately one month after the storm, refinery activity remained at multi-year lows.
Total rainfall hit 60.58 inches, a record for a single storm in the continental United States. In total, Harvey dumped 53.4 million acre-feet of water on Texas. The sheer weight of the water depressed the Earth's crust. Houston sank two centimeters as a result. But it rebounded once the waters receded.
August 25, 2017: Harvey reached landfall at Fulton near Corpus Christi, Texas, with 130 mph winds. There was a peak wind gust of 145 mph at the Aransas County Airport. A storm surge exceeded 12 feet above ground level.
August 26: Harvey moved on to Houston. It remained there for four days. A large portion of the area received more than three feet of rainfall. That level of flooding had a less than 0.1% chance of occurring.
August 29: Harvey made landfall for a third time as it hit the coastal cities of Port Arthur and Beaumont, Texas on the border of Louisiana. Rainfall fell at a rate of two to three inches per hour.
August 31: An Arkema chemical plant in Crosby, Texas ignited. The chemicals required refrigeration to stay inert. When the storm disabled the cooling equipment, temperatures rose and the chemicals ignited.
September 1: Harvey dropped about a foot of rain on Nashville, Tennessee.
Three Ways Global Warming Made Harvey Worse
Climatologists agree that global warming very likely contributed to Harvey’s impact. Studies found that the amount of rainfall was 38% higher because of it.
There are three reasons for this phenomenon. The convergence of all three effects allowed Harvey to drop feet of rain instead of inches.
First, the Gulf region air temperatures are hotter than in the past. This allows the air to hold more moisture. Warmer air holds more moisture, so it's less likely to rain. But when it does, the water descends in buckets.
Second, rising sea levels make flooding more likely near Gulf Coast cities. The average global sea level has risen 8.9 inches between 1880 and 2015. Climatologist Michael Mann estimates that made Harvey's storm surge six inches higher than it would have been decades ago.
Third, climate change allows hurricanes to remain in place longer. Since 1949, the storm speeds have slowed by 10%. Climate change does this by weakening the jet stream. That’s a river of wind high in the atmosphere that races from west to east at speeds up to 275 miles an hour. It undulates north and south as it goes. It's driven by temperature contrasts between the Arctic and temperate zones. But the Arctic is warming faster than the rest of the globe. That slows down the jet stream.
According to M.I.T. models, global warming will create more hurricanes by 2035. Of those, 11% will be Category 3, 4, and 5. There will be 32 super-extreme storms with winds above 190 miles per hour.
Harvey's Damage Compared to Other Natural Disasters
Hurricane Harvey's damage was $125 billion when adjusted for inflation. That's less than Katrina's $160 billion cost. But it's much more than the $90 billion incurred by Hurricane Maria, another 2017 storm.
Harvey's extensive damage was unusual because it remained over a major metropolitan area for a longer period of time than most hurricanes.
For a wider comparison, the cumulative cost of the five worst hurricanes on record is $495 billion in damages. The bar chart below shows a breakdown.