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Antonia Sebastian (Photo: Jos Wassink)
Hydrologist Antonia Sebastian comes from Texas and is postdoc in Delft. (Photo: Jos Wassink)

The flooding of Houston, Texas, by hurricane Harvey has taken on biblical proportions. Hydrologist Dr Antonia Sebastian (29) from Rice University comments from her postdoc position in Delft.

You come from Texas, you have friends and family there. What do you hear from them about the flooding?

All of the people I talked to are still safe. A few people have a small amount of water in their home, others I’ve heard from have more water in their houses and have had to leave their homes. So far the information provided by emergency management in Houston has been very good. Houstonians had lots of warning, and they knew that flooding was coming. On Friday schools were already cancelled and, for many, work was cancelled so people could stay home and shelter in place. But still, I think everyone was quite shocked by the amount of rain that fell. People woke up on Sunday to an amazing amount of water and that was really shocking.

Is it disruptive to the city?

“It is incredibly disruptive. Schools everywhere in Houston are closed for the whole week at least. Many schools are flooded, so they’ll be closed for longer. Every single roadway is affected, all of the major freeways. So basically, on Friday people were asked to go home and not leave their houses. So in that sense it is quite disruptive.”

Are there any differences in neighbourhoods in the sense that poorer areas are worse hit?

“Interestingly, that is often true in coastal events. But because this is a rainfall event, it has affected everyone. In fact, some affluent neighbourhoods have now been affected three years in a row with a foot or more water in their homes.”

Is flooding as common as that?

It hasn’t been as common as that, but we have had a couple of extreme events the last three years. There was the Memorial Day Flood in 2015 at the end of May. The following year we had the Tax Day Flood in April. Both of these events produced hundred year rainfalls in the City of Houston and caused extreme flooding. And now many Houstonians have been hammered again. You see that after these events many people have just moved back into their homes and a few weeks later they are flooded again and they have to start over.

There have been a lot of studies on the coastal defence of Houston and the Galveston Bay. Is there any way that hydraulic engineering could mitigate these rainfall events?

In short: yes. But in this case we’re talking ‘room for the river’-like projects, spatial planning projects, setbacks from the vulnerable areas, incorporating parks into the city structure, elevating homes, flood proofing homes. From a hydraulic engineering standpoint, we could improve the drainage infrastructure. In terms of Harvey, probably the effects could have been reduced by hydraulic engineering, but I’m not sure they can be fully mitigate them in the existing system given the amount of rain that has fallen because this is just … extreme. Never-seen-before kind of thing.” 

Never seen before, but the third year in a row?

“The previous hurricanes were smaller. At a spatial scale, this one is unique.”

Do people perceive hurricane Harvey as a sign of climate change, as happened after hurricane Katrina?

Major flood events are normal in Houston. In the history of Houston since the 1800s there have always been major floods. Houstonians know it’s always going to come again, but the intensity of these recent events and the frequency with which they are occurring is becoming more extreme. In terms of public perception, there are news articles and editorials and they are questioning whether there is potential link to climate change.

What is your personal opinion?

“I am not a climate scientist, but I can say that in the Gulf of Mexico, there is the link between the water temperature and  Harvey’s development. But in terms of its stalling over Houston and dropping so much rain. It’s just … unprecedented. Unbelievable.”

Read also:

Washington Post: The Post’s latest coverage of Hurricane Harvey (August 28, 2017)

 

A Texas National Guardsman carries a resident from her flooded home following Hurricane Harvey in Houston, Aug. 27, 2017. Army National Guard photo by Lt. Zachary West
A Texas National Guardsman carries a resident from her flooded home following Hurricane Harvey in Houston, Aug. 27, 2017. Army National Guard photo by Lt. Zachary West
An aerial view shows severe flooding caused by Hurricane Harvey near Rockport, Holiday Beach and Port Aransas, Texas, Aug. 27, 2017. Army National Guard photo
An aerial view shows severe flooding caused by Hurricane Harvey near Rockport, Holiday Beach and Port Aransas, Texas, Aug. 27, 2017. Army National Guard photo

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