Interesting Take on Levee system failure (Dutch Style)

[heyholetsgogrant]

http://kohlmanobserver.mydd.com/story/2005/9/1/202720/0815

[twa]

I would not use Galveston as a example as this writer does.

A major hurricane will devastate it.

http://www.chron.com/cs/CDA/ssistory.mpl/front/3344353

HoustonChronicle.com -- http://www.HoustonChronicle.com | Section: Front page

Sept. 8, 2005, 5:37AM

A mini-New Orleans? Galveston ponders its vulnerabilities

Leaders say that disaster has served as 'wake-up call'

By ERIC BERGER

Copyright 2005 Houston Chronicle

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The Big Easy may eclipse Galveston in magnitude, style and hipness, but by other measures the two Gulf coast cities aren't so dissimilar.

Both have industrial ports, sweaty climates and celebrate Mardi Gras with abundant beer, balconies, beads and breasts. They also share one other critical link: Both cities rely on long, sturdy walls to survive monster hurricanes.

As New Orleans discovered last week in Hurricane Katrina's wake, however, walls can fail. So where does this leave Galveston, arguably the country's second-most vulnerable city to a hurricane, behind only New Orleans?

"If they didn't feel a chill in their blood, they should have," said Bill Dupre, an associate professor of geosciences at the University of Houston.

By the reckoning of public officials who safeguard the island, Galveston residents would have only one defense from a storm like Katrina: evacuation. Such a storm, said Eliot Jennings, Galveston County's emergency management coordinator, would do a "whole lot of damage."

The island city's mayor, Lyda Ann Thomas, went further.

"I think the island would be destroyed, wiped out," she said. "There wouldn't be anything left. I do think Galvestonians are paying attention to what happened, and people who thought they might not evacuate will now think twice before they decide whether to leave the island."

While New Orleans counted on its levee system, Galveston's sense of security comes from a 15-foot wall. After the great storm of 1900, which killed 8,000, Galveston's leaders constructed a seawall along much of the island's eastern end. They also raised the city directly behind it from a peak of 8 feet above sea level to about 15 feet.

The island now reaches its highest point at the seawall, gently sloping back to sea level at bayside.

A Katrina-size storm would not destroy the seawall, and indeed the wall would absorb much energy from the biggest, crashing waves. But Katrina's storm surge crested at 22 feet, enough height to easily clear the seawall. And the city has no protection from bayside waters.

"The island would be completely underwater," said Donald Van Nieuwenhuise, director of petroleum geoscience programs at UH. "And it's less protected from winds than New Orleans. The only good thing is that, once the rain and winds went away, water would begin to recede."

A barrier island

Galveston's founders, including Gail Borden Jr., the inventor of condensed milk, made a poor decision when siting their burg in 1836. The city rests on a barrier island, essentially a glorified sandbar.

Ever-shifting, barrier islands are transient coastal features. They gradually build up from silt and sand deposited on the coast by inland rivers. The state's barrier islands slowly have died as Texas has dammed up many of its rivers.

Or the islands may die quickly, in the case of some islands hit by storms that lash the land and either carry beach sand offshore or cut breaches through islands.

Two years ago, public officials spent millions of dollars to renourish starving beaches on the western end of Galveston Island, adding acres of shoreline. That summer, a minor hurricane, Claudette, made landfall in Texas near Port O'Connor.

Although the storm only produced about 45 mph winds in Galveston, it stripped away one-third of the new beach, Van Nieuwenhuise said.

Geologically, then, Galveston should only become more vulnerable to hurricanes. Not only is it losing its sliver of protective beach, which might absorb the surges from minor storms, but it also may be sinking.

Geoscientists agree the island has sunk about 2.5 feet in the century since engineers raised it. It's not entirely clear why. Some loss, scientists say, must be caused by rising sea levels. Some also may be caused, simply, by a sinking Gulf coast.

Reasons disputed

A National Oceanic and Atmospheric Administration report published last year suggests this natural subsidence has accelerated in recent decades. Although the report remains controversial, its lead author, Louisiana State University geologist Roy Dokka, made meticulous measurements to back up his conclusions that the upper Gulf Coast slowly is falling into the water.

"There may be something wrong with Dokka's estimates, but if there is something wrong, I'd hasten to add that I don't know what it is," said John Anderson, a Rice University oceanographer who has just written a book called Origins and Destiny of the Upper Texas Coast .

What is clear is that an island just barely above sea level, and losing coastline, can afford to sink no farther.

Nowhere can the problem be more acutely felt than the island's western end, which in most places lies fewer than 5 feet above sea level. This area also has some of the highest coastal land-loss rates in the state. The University of Texas at Austin's Bureau of Economic Geology estimates most of west Galveston Island loses 9 feet of coast a year.

That pace of land loss would put half the Pirates' Beach subdivision under water within 50 years.

Perhaps most frustrating for some scientists and environmentalists is that this most-precariously perched section of the island is also where development has raced ahead.

It's not difficult to see why: cheap land, the best beaches and lovely sunrises over the dunes. When there's no hurricane looming in the Gulf of Mexico, it's a little slice of paradise, residents say.

"No one can blame a seeker for building a dream home near the Gulf," said Mark Muhich, chairman of the Sierra Club Galveston Group.

"However, when real estate developers fund policies that will damage and destroy the very barrier island they profess to love, those of us who would protect the natural beauty of Galveston Island must respond."

Critics target developments such as the $500 million project by Centex Destination Properties near the San Luis Pass, which they say are being built on historically unstable coastline. Attempts were made to get comments from Centex without success, but the developer has said it will widen the natural dune system to protect the coast.

New understanding

Dupre and other scientists say city councils and county governments face intense pressure to approve the projects because they offer a premium on property tax value.

"There's just nothing you can do to protect these homes from a major storm," Dupre said. "At a minimum, the first few rows of houses will be leveled."

He compares the Galveston coastline to Alabama's unprotected Dauphin Island, utterly destroyed by Katrina.

It wouldn't even take a big Category 4 hurricane, he said. A big enough Category 2, between wind and storm surge, probably would doom a lot of houses along the island's west end.

Jerry Mohn, president of the West Galveston Island Property Owner's Association, said the devastation of New Orleans has hit home in his coastal community.

"The very same thing could happen to our island, particularly to the West End," Mohn said. "People will go. This is absolutely the biggest wake-up call we could have received."

eric.berger@chron.com

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