Hurricane Katrina is thought to have killed around 1,800 people, but it was not nearly the most deadly hurricane in terms of U.S. casualties. That “honor” belongs to the Galveston Hurricane of 1900, which wiped out the city and killed an estimated 6-8,000 people.

The storm surge was about 16 feet, and the highest elevation in Galveston at the time was less than 9 feet above sea level. Some had talked of building a seawall before the hurricane, but most residents and the government didn’t consider it necessary. That view may have been influenced by the opinion of Isaac Kline, Galveston Director of the Weather Bureau, who wrote a newspaper article in the Galveston Daily News in 1891 saying it was impossible for a significant hurricane to hit the island.

Kline paid a personal price for that mistake, losing his pregnant wife in the hurricane.  In addition, he is credited with saving many lives in later years when he was Chief Forecaster in New Orleans.  He accurately predicted a number of floods and insisted on the public being warned despite strong political resistance from the local government and higher-ups in the Weather Bureau. In the case of the Great Flood of 1927, New Orleans officials tried to censor Kline’s warnings because they were afraid the bad publicity would hurt commerce.

That’s reminiscent of the movie Jaws, in which the sheriff wanted people warned about the killer shark, but local officials didn’t believe the threat and were afraid warnings would hurt tourism. This been a common theme in many other monster and disaster movies — and apparently it’s not unrealistic. In the days before Katrina, New Orleans Mayor Ray Nagin delayed ordering a mandatory evacuation because he was afraid the city would be sued for closing hotels and other businesses.

After the 1900 hurricane, Galveston was built up with dredged sand and raised to be as much as 17 feet higher than it was before, and it has a 17-foot seawall.

It now looks like Hurricane Ike will hit Texas south of Galveston as a Category 3 hurricane, but some forecasters predict it could be a Category 4 by that point — like the 1900 storm.  NOAA’s S.L.O.S.H. model indicates the worst-case storm tide (surge + tide) at Galveston would be 19-22 feet. (And 28 feet at Houston!) That, again, is a worst-case scenario — though the margin of error for that model is +/- 20%.

A mandatory evacuation has been ordered for low-lying areas of Houston and Galveston. However, Galveston Mayor Lyda Ann Thomas insisted that evacuation only be voluntary for the rest of the island, because the seawall would protect them. “Right now, we feel that sheltering in place is the best option for our citizens to take,” she said. A mandatory evacuation, she said, “is the last thing we want to do” and not possible this close to the storm’s landfall; the window of time to do that has passed, she said.

Sources:
http://www.weather.gov/mdl/psurge/
http://www.wunderground.com/blog/JeffMasters/
http://www.galvnews.com/story.lasso?ewcd=ab114e3ab508daaf
http://www.1900storm.com/
http://en.wikipedia.org/wiki/Galveston_Hurricane_of_1900
http://en.wikipedia.org/wiki/Isaac_Cline
http://www.islandnet.com/~see/weather/history/icline3.htm
Bruce Nolan, “Katrina Takes Aim”, New Orleans Times-Picayune, Aug. 28, 2005.

UPDATE: Mayor Thomas backed down and ordered a mandatory evacuation of the whole island on Thursday morning, Sept. 11th. So much for it being “not possible.” Her earlier advice disappeared from most online news articles when they were updated, though at the moment it’s still on the Galveston County Daily News Web page cited above.

UPDATE: Here’s the latest Ike analysis from former NOAA hurricane hunter Dr. Jeff Masters. He’s not so sure Ike will be at Category 4 hurricane at landfall anymore, but:

“…Ike is now larger than Katrina was, both in its radius of tropical storm force winds — 275 miles — and in it radius of hurricane-force winds — 115 miles. … Ike’s huge wind field has put an extraordinarily large volume of ocean water in motion. … Ike will probably inundate a 180-mile stretch of Texas coast from Port O’Connor to just north of Galveston with a 10-15 foot storm surge … even if Ike is a Category 1 storm at landfall.  The latest experimental storm surge forecast from NOAA’s SLOSH model shows a 10% chance that Ike’s storm surge will exceed 15-21 feet at Galveston. The Galveston sea wall is 17 feet high, so it may get overtopped.

“The amount of water Ike has put in motion is about 50% greater than what Katrina did, and thus we can expect Ike’s storm surge damage will be similar to or greater than Katrina’s. …  Dr. Mark Powell of NOAA’s Hurricane Research Division [proposed] as a better measure of the destructive power of a hurricane’s storm surge than the usual Category 1-5 Saffir-Simpson scale. For example, Hurricane Katrina hit Mississippi as a strong Category 3 hurricane, yet its storm surge was more characteristic of a Category 5 storm.

Dr. Powell came up with a new scale to rate potential storm surge damage … The new scale ranges from 1-6. Katrina and Wilma at their peaks both earned a 5.1 on this scale. At 9:30 am EDT this morning, Ike earned a 5.6 on this scale, the highest kinetic energy of any Atlantic storm in the past 40 years. …

“NOAA’s Wavewatch III model is predicting wave heights up to 13 meters [43 feet] from Ike on Friday. … NOAA’s experimental storm surge forecast is calling for a 10% chance that the storm tide from Ike will reach 24-27 feet on the south and east sides of Houston.”