Effects of Katrina greatly magnified by environmental damage

[Uiler]

This interesting article describes the worse case scenario for New Orleans. However in an interesting bit it describes how the effects of the cyclone will be greatly magnified by environmental damage and human modification of the landscape around the New Orleans area:

http://news.yahoo.com/news?tmpl=story&u=/ap/20050828/ap_on_re_us/katrina_the_big_one_1

Experts have warned about New Orleans' vulnerability for years, chiefly because Louisiana has lost more than a million acres of coastal wetlands in the past seven decades. The vast patchwork of swamps and bayous south of the city serves as a buffer, partially absorbing the surge of water that a hurricane pushes ashore.

Experts have also warned that the ring of high levees around New Orleans, designed to protect the city from floodwaters coming down the Mississippi, will only make things worse in a powerful hurricane. Katrina is expected to push a 28-foot storm surge against the levees. Even if they hold, water will pour over their tops and begin filling the city as if it were a sinking canoe.

After the storm passes, the water will have nowhere to go.

In a few days, van Heerden predicts, emergency management officials are going to be wondering how to handle a giant stagnant pond contaminated with building debris, coffins, sewage and other hazardous materials.

"We're talking about an incredible environmental disaster," van Heerden said.

He puts much of the blame for New Orleans' dire situation on the very levee system that is designed to protect southern Louisiana from Mississippi River floods.

Before the levees were built, the river would top its banks during floods and wash through a maze of bayous and swamps, dropping fine-grained silt that nourished plants and kept the land just above sea level.

The levees "have literally starved our wetlands to death" by directing all of that precious silt out into the Gulf of Mexico, van Heerden said.

It has been 40 years since New Orleans faced a hurricane even comparable to Katrina. In 1965, Hurricane Betsy, a Category 3 storm, submerged some parts of the city to a depth of seven feet.

Since then, the Big Easy has had nothing but near misses. In 1998, Hurricane Georges headed straight for New Orleans, then swerved at the last minute to strike Mississippi and Alabama. Hurricane Lili blew herself out at the mouth of the Mississippi in 2002. And last year's Hurricane Ivan obligingly curved to the east as it came ashore, barely grazing a grateful city.

This is also mentioned in another article:

http://www.chron.com/cs/CDA/ssistory.mpl/nation/3329008

When water is forced into the lake and over the lake-side levee, it will settle in the city, Cowan said.

"There is only one place for the water to go, and that is the city of New Orleans," he added.

If floodwater does reach to the top of the levees, it will take a long time to subside, said Joseph Suhayda, retired former director of the Louisiana Water Resources Research Institute.

After the storm, public works officials would likely breach the levees, allowing every point in the city at or above sea level to drain. For areas below sea level, he said, it would likely take weeks to restore New Orleans' pumping stations and remove the water.

Longtime warnings
Walker and other storm and tidal experts have seen the warnings for years. In 2000, State Farm Insurance, one of the state's leading insurance providers, severely curtailed writing new policies in coastal Louisiana because of the growing storm danger.

Subsidence has caused the levees to sink. Also, 50 miles of tidal wetlands that once stood between New Orleans and the Gulf are eroding.

The erosion largely is the result of damage to the ecosystem caused by the construction of river levees, which interrupt natural flooding cycles that replenish the marshes, and the dredging of oil canals, which allow intrusion of vegetation-killing salt water.

"We lose 1,000 acres of tidal marshes a year through erosion," Cowan said. "The marshes are our buffer. If you lose that buffer, that means the tidal surge will hit you much quicker and with much more force."

Now I don't want to be seen as gloating. I've been in a massive flood before (though nowhere near what New Orleans is going to get) so I know what it is like. People screaming "Turn back. The bridge is completely underwater, you'll never make it!", praying that the dam will hold, wading out into waist height water in driving rain, putting buckets out to catch rain water afterwards because all the water pipes got washed away in the flood and that's the only way to get clean water, etc. so my sympathies go out to the people of New Orleans.

We hear about similar things happening in developing countries all the time, esp. how massive deforestation is causing much more massive floods and landslides. However, this is now an example much closer to home than off in some poor country. I think that this really drives home the reason why we humans should be concerned about the environment. Not because the cute cuddly animals are going to get killed or because it makes us feel good about how noble we are but because the damage we do will eventually come and bite us in the ass. It's not about saving the world or even saving nature but saving *ourselves* or at least saving the comfortable life that we enjoy. It's why I'm an environmentalist even though I dislike nature (it's too dirty for me, I'm an indoors climate-controlled girl myself). Sheer self-interest.

 

[Truronian]

I've always thought New Orleans is in a dangerously prone position, though I don't see the flood waters staying indefinately. Hopefully the city will be prepared

 

[frekk]

Well this is an interesting thread to bump in light of recent events.