John Mutter: We’ll never know exactly what the [fatality number] is, but let’s say it’s close to 2,000. You have to go back to 1900 to have a similar event in the United States. It’s more typical of poor countries today, or our country a long time ago. So something weird was going on with Katrina. I was curious about exactly how the counting was being done, who was included, and why the fatality rate was so high.
I went to New Orleans several times, and I asked people how the determination of the cause of death was being done, to determine whether they were hurricane victims or not, how long after the event did they stop counting ... and tried to get a sense of what they were doing.
I also had a website where people could write in and describe the circumstances of the death of a relative. Sometimes it happened quite a few days or weeks after the event. Particularly among elderly people who were displaced, if they weren’t in good condition, which most of them were not, they would often die ... of exacerbation of existing conditions, like heart disease or respiratory failure. Particularly, say, if they lose track of their medications, which happens a fair bit.
Khazan: What were the main differences between Katrina in New Orleans and what we can tell of Harvey so far, in terms of lethality?
Mutter: What looks to be different is not the strength. It’s not unusual in wind speed. What seems unusual about Harvey is the extent of rainfall. When people talk about it being unprecedented, that’s what they’re talking about.
The fatalities that we saw in Sandy and in Katrina were mostly, not exclusively but mostly, seawater from storm surge. In Katrina, storm surge [a huge wave caused by high winds] came up the industrial canal, over top of the levees, and then breached a number of other levees—what came in was seawater from the ocean.
It seems like what’s going on [in Houston is] that the rainfall is biblical. If you’re inland, and it’s raining like hell, and streams that don’t normally flood start flooding, and you can’t figure out where to go, it can be deadly.
Khazan: How did people die during Katrina? Is that a risk here?
Mutter: A number of them were straightforward drowning. People were trapped in their houses, couldn’t get to upper levels, and drowned. But then there were a number who died from the exacerbation of existing injuries. If you have a weak heart, and you’re struggling to get out somewhere, you’re putting yourself at substantial risk.
Khazan: How does the geography of Houston, compared to New Orleans, affect the risks from tropical storms?
Mutter: Houston is flatter. If you’ve ever been to Houston, it’s really a flat place. New Orleans had what they call the bowl. A lot of it is below sea level. When the levees failed, and the seawater came in, it just stayed there. It took days to get out. [Houston] shouldn’t stay flooded as long or as extensively as New Orleans did.