Hous­ton sky­line in­ten­si­fied rain from Har­vey, re­searchers say

The State (Sunday) - - Stay Connected - BY SETH BORENSTEIN

Hu­mans helped make re­cent dev­as­tat­ing U.S. hur­ri­canes wet­ter but in dif­fer­ent ways, two new stud­ies find.

Hur­ri­cane Har­vey snagged on the sky­scrapers of Hous­ton, caus­ing it to slow and dump more rain than it nor­mally would, one study found. The city’s mas­sive amounts of paving had an even big­ger im­pact by re­duc­ing drainage. Land de­vel­op­ment in the metro area, on av­er­age, in­creased the chances of ex­treme flood­ing by 21 times, study au­thors said.

A sec­ond study looked at last year’s ma­jor Hur­ri­canes Maria and Irma and 2005’s deadly Ka­t­rina and used com­puter sim­u­la­tions to see what would have hap­pened if there had been no hu­man­caused global warm­ing. The study found that cli­mate change sig­nif­i­cantly in­creased rain­fall from those three storms, but did not boost their wind speed.

Both stud­ies were in Wed­nes­day’s jour­nal Na­ture.

Hous­ton was a lit­eral drag on Har­vey as it sloshed through, with the storm get­ting tripped up by the sky­scrapers, said study co-au­thor Gabriele Vil­lar­ini, a civil and en­vi­ron­men­tal en­gi­neer­ing pro­fes­sor at the Univer­sity of Iowa.

Co-au­thor Gabe Vec­chi, a cli­mate sci­en­tist at Prince­ton Univer­sity, said that forced the storm to move up higher, caus­ing more con­cen­trated rain over Hous­ton and slow­ing, which also made more rain.

He com­pared it to a river run­ning over rocks, cre­at­ing bub­bles.

“That’s sort of what’s go­ing on here,” he said.

This ef­fect is dwarfed, though, by the paving and build­ing that don’t al­low wa­ter to sink into the ground, Vec­chi said.

Har­vey’s record rain­fall reached 5 feet in one spot near Hous­ton. The sci­en­tists used com­puter sim­u­la­tions to see the ef­fects of ur­ban­iza­tion. In parts of the Hous­ton metro area, the ef­fects of de­vel­op­ment ranged from a 10 per­cent higher risk of ex­treme flood­ing in the less de­vel­oped north­west to nearly 92 times the risk in the north­east, they re­ported.

That’s on top of the unique weather pat­terns that made Har­vey slow down and stall and cli­mate change which brought more wa­ter into the storm, Vec­chi said.

MIT hur­ri­cane and cli­mate ex­pert Kerry Emanuel, who wasn’t part of the study, called the Har­vey study “a real ad­vance in our un­der­stand­ing of hur­ri­cane im­pacts on ur­ban ar­eas.”

But Texas state cli­ma­tol­o­gist John Nielsengam­mon wasn’t con­vinced. He said the team used generic shapes in­stead of the ac­tual Hous­ton sky­line. He said the storm’s wind speeds may have slowed, but that’s dif­fer­ent from the storm’s for­ward move­ment slow­ing.

LM OTERO AP

Flood­wa­ters from Trop­i­cal Storm Har­vey over­flow from Buf­falo Bayou in down­town Hous­ton, Texas. A study re­leased on Wed­nes­day says that de­vel­op­ment in Hous­ton on av­er­age in­creased the ex­treme flood­ing risk by 21 times.

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