Hurricane Harvey (2017): Record Rainfall and the Houston Floods

Hurricane Harvey was a powerful Atlantic hurricane that struck the Texas coast in August 2017 and then stalled, unleashing the heaviest rainfall ever recorded from a tropical cyclone in the United States. Over several days up to 60 inches of rain fell on south-eastern Texas, causing catastrophic flooding in Houston, the country’s fourth-largest city. Harvey killed about 107 people and caused some 125 billion US dollars of damage, making it one of the costliest natural disasters in US history.

From a weak storm to a major hurricane

Harvey formed east of the Lesser Antilles on 17 August 2017 and crossed the Caribbean as a weak tropical storm, degenerating into a tropical wave on 19 August. Its remnants drifted across the Yucatán Peninsula into the Bay of Campeche, where it regenerated as a tropical depression on 23 August.

Over the very warm waters of the Gulf of Mexico it then intensified rapidly, growing from a tropical depression into a Category 4 hurricane in a little over two days. Forecasters warned not only of high winds and storm surge but of a prolonged, extreme rainfall event, because weather models showed the storm would slow to a crawl after landfall.

Landfall near Rockport

Harvey made landfall at about 10 p.m. on 25 August 2017 on San José Island and then near Rockport, on the central Texas coast, with sustained winds of about 130 miles per hour (215 km/h). It was the first major hurricane to make landfall in the United States since Wilma in 2005, and the strongest to strike Texas since Hurricane Carla in 1961.

The winds and a storm surge of up to about 12 feet devastated Rockport, Port Aransas, Fulton and nearby towns, destroying or damaging thousands of homes and businesses. But the greatest damage was still to come.

The stall and the rain

After landfall Harvey weakened to a tropical storm but became trapped between two areas of high pressure, with no steering winds to move it away. For about four days it drifted slowly near the coast, part of its circulation remaining over the Gulf and feeding it a constant supply of moisture.

Bands of torrential rain repeatedly passed over the same areas. Much of Greater Houston received 30 to 50 inches (760-1,270 mm) of rain, and the highest total, 60.58 inches (1,539 mm), was measured near Nederland, between Beaumont and Port Arthur, setting a US record for a tropical cyclone. The amount of water that fell on Texas and Louisiana was estimated at tens of trillions of gallons.

Houston under water

Houston is built on flat, low-lying land crossed by slow-moving bayous, with clay soils that absorb little water and vast areas of paved development. As the rain continued from 26 August, bayous overflowed and water poured into neighbourhoods, motorways and homes, including many outside official flood zones.

Ahead of the storm, local officials had not ordered a city-wide evacuation, judging that sending millions of people onto the roads would be more dangerous; the decision was debated afterwards. Thousands of people had to be rescued from rooftops and flooded houses by emergency services, the National Guard and the Coast Guard, joined by volunteers with private boats, including the so-called “Cajun Navy” from Louisiana. The George R. Brown Convention Center in downtown Houston sheltered around 10,000 people at its peak.

To protect central Houston, the US Army Corps of Engineers began controlled releases from the Addicks and Barker flood-control reservoirs on 28 August, as water rose to record levels. The releases, and water backing up behind the dams, flooded thousands of homes in the west of the city, and homeowners later won a federal court ruling on their claims against the government.

Further impacts

Harvey moved back over the Gulf and made a final landfall as a tropical storm near Cameron, Louisiana, early on 30 August, then moved inland and weakened. Severe flooding hit Beaumont and Port Arthur, where the city’s water supply failed for several days.

Flooding also caused industrial accidents. At the Arkema chemical plant in Crosby, north-east of Houston, power failures stopped the cooling of unstable organic peroxides, which caught fire from 31 August, forcing an evacuation zone. Refineries and petrochemical plants along the Gulf Coast shut down, briefly pushing up fuel prices across the United States, and several facilities released pollutants.

Deaths, damage and recovery

The National Hurricane Center counted 68 direct deaths in Texas, mostly people who drowned in floodwater, often in vehicles, and about 35 indirect deaths. Roughly 300,000 buildings and up to half a million vehicles were flooded in south-eastern Texas, and around 30,000 people were displaced into shelters. Its estimated damage of about 125 billion US dollars tied it with Hurricane Katrina as the costliest US hurricane at the time.

Recovery took years. Many flooded households lacked flood insurance, and federal grants and loans were slow to arrive. In August 2018 voters in Harris County approved a 2.5 billion dollar bond to fund flood-control projects, and Texas later planned large coastal and drainage schemes. The name Harvey was retired from the Atlantic list in 2018.

The flooding also had wide economic effects. The Port of Houston and nearby ship channels, among the busiest in the United States, closed for several days, and roughly a fifth of the country’s oil refining capacity was temporarily shut down. Schools in Houston reopened weeks late, and many small businesses never recovered. At the same time, the response of ordinary citizens, who used their own boats and trucks to rescue neighbours and strangers and volunteered at shelters, became one of the most remembered aspects of the disaster.

Federal agencies reviewed their performance after a season in which Harvey, Irma and Maria struck within a few weeks of each other. FEMA’s own after-action report found that its staff and supplies had been stretched thin, and that lessons from Harvey needed to be applied to future catastrophes.

Climate change and urban growth

Scientific studies published soon after the storm estimated that human-caused warming had made Harvey’s rainfall significantly heavier, by roughly 15 to 38 per cent according to different analyses, because a warmer atmosphere and Gulf hold more moisture. Researchers also pointed to Houston’s rapid, loosely regulated growth, which had paved over prairie and wetlands that once absorbed rain. Harvey thus became a central case in debates about adapting cities to more extreme weather. Just weeks later, Hurricane Maria struck Puerto Rico, completing one of the most destructive hurricane seasons on record.

Timeline

• 2017, 17 August: Harvey forms east of the Lesser Antilles.
• 2017, 19 August: It degenerates into a tropical wave over the Caribbean.
• 2017, 23 August: Harvey regenerates in the Bay of Campeche and begins rapid intensification.
• 2017, 25 August, about 10 p.m.: Harvey makes landfall near Rockport, Texas, as a Category 4 hurricane.
• 2017, 26-29 August: Torrential rain floods Houston and south-eastern Texas.
• 2017, 28 August: Controlled releases begin from the Addicks and Barker reservoirs.
• 2017, 30 August: Harvey makes its final landfall near Cameron, Louisiana.
• 2017, 31 August: Fires break out at the flooded Arkema chemical plant in Crosby.
• 2018, 25 August: Harris County voters approve a 2.5 billion dollar flood-control bond.

Why it matters

Harvey showed that a hurricane’s deadliest threat can be water rather than wind, especially when a storm stalls over a large, low-lying city. It set a national rainfall record, exposed weaknesses in flood planning and insurance, and became one of the clearest examples of how a warming climate and urban development can combine to magnify disasters.