Houston, we have a problem: Layout of the Texas city made hurricane Harvey flooding 21 times WORSE (and climate change boosted rainfall for Katrina, Irma and Maria by almost 10%)

  • Two new studies have highlighted the effects of human activity on hurricanes
  • Researchers found urbanization has made Houston more susceptible to floods
  • The model suggests this raised the risk of flooding by 21 times during Harvey
  • Other study says climate change made rainfall worse in Katrina, Irma, and Maria

Human activity is causing storms to have a much more devastating impact than in the past, a pair of studies has warned.

While the effects of human activity on climate change has been widely discussed in recent years, researchers say it’s not just storm intensity we need to worry about.

Urbanization has made some areas far more susceptible to extreme flooding – a consequence a new study says was especially apparent in Houston during hurricane Harvey.

The new models of rainfall and urbanization show how urban development has raised the risk of hurricane-related flooding by 21 times on average.

At the same time, climate change has caused more rainfall during major storms in the recent past, including Katrina, Irma, and Maria, and the issue is only expected to get worse.

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Urbanization has made some areas far more susceptible to extreme flooding – a consequence a new study says was especially apparent in Houston during hurricane Harvey. Flooded homes near Lake Houston following the August 2017 storm are shown above

Urbanization has made some areas far more susceptible to extreme flooding – a consequence a new study says was especially apparent in Houston during hurricane Harvey. Flooded homes near Lake Houston following the August 2017 storm are shown above

The two new papers published in the journal Nature this week highlight the increasing risks posed by hurricanes in the face of climate change, much of which has been exacerbated by human processes.

In one study, researchers from the University of Iowa modelled the effects of urbanization on rainfall during hurricane Harvey, revealing how the city’s layout worsened the effects of the storm.

According to the team, the topography increased atmospheric drag, promoting heavier rainfall.

And, the extensive coverage of concrete and asphalt made flooding more extreme.

‘Houston has had the largest urban growth and the fifth-largest population growth in the United States over the period 2001-2011,’ the researchers explain in the paper.

‘The increase in asphalt and concrete has led to an increasing runoff (that is, the ratio between runoff and precipitation) across many watersheds in the area, pointing to reduced infiltration and larger runoff for a given rainfall value.

‘This increase in population and urbanization, combined with the flat clay terrain that characterizes this area, represents a very problematic mix from a flood perspective, despite the flood mitigation measures that have been put in place.’

In one study, researchers from the University of Iowa modeled the effects of urbanization on rainfall (shown above) during hurricane Harvey, revealing how the city’s layout worsened the effects of the storm

In one study, researchers from the University of Iowa modeled the effects of urbanization on rainfall (shown above) during hurricane Harvey, revealing how the city’s layout worsened the effects of the storm

In the second study, researchers from Lawrence Berkeley National Laboratory found that climate change has dramatically increased hurricane rainfall in recent years.

They also warn could be even worse in decades to come.

The team estimates that rainfall was 4-9 percent higher than average during hurricanes Katrina, Irma, and Maria.

NATURAL DISASTERS HIT RECORD LEVELS DURING 2017 

A total of 16 disasters cost the US $1 billion or more in 2017, said the report by the National Oceanic and Atmospheric Administration.

The previous costliest year for the US was 2005 with losses of $215 billion driven in large part by Hurricanes Katrina, Wilma and Rita.

These events included 1 drought event, 2 flooding events, 1 freeze event, 8 severe storm events, 3 tropical cyclone events, and 1 wildfire event.

Overall, these events resulted in the deaths of 362 people and had significant economic effects on the areas impacted.

Last year, the western wildfire season -- which ravaged large parts of California - cost $18 billion, 'tripling the previous US annual wildfire cost record,' said the report.

Hurricane Harvey, which dumped some 50 inches (127 centimeters) of rain on Texas, cost $125 billion, second only to 2005's Hurricane Katrina in historical records of billion-dollar disasters, going back four decades.

Hurricane Maria, which flattened much of Puerto Rico, cost $90 billion, while Hurricane Irma, which plowed into the Caribbean and Florida, cost $50 billion.

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While storm intensities, based on wind speed and pressure at sea level, did not appear to show substantial effects, the researchers say predicted climate change will likely cause winds to spike by 6 to 29 knots in the future.

This will also lead to a 25 to 30 percent increase in rainfall in worst-case scenarios.

‘These future changes in tropical cyclone intensity and rainfall could exacerbate societal impacts associated with ocean wind-waves, storm surge, flooding, and forests and ecosystems,’ the researchers say.

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