The 20-foot storm surge from Katrina shoved the Gulf of Mexico up the inlets feeding Lake Pontchartrain, eventually breeching the levee and flooding New Orleans from the north. Ken Ringle must have been channeling the voodoo spirits of the Big Easy when he wrote in an Aug. 29 story for the Washington Post – “The real nightmare has always been the prospect of a Wagnerian hurricane like Katrina coming ashore so that its strongest winds push the Gulf of Mexico into the eastern-facing entrance to Lake Pontchartrain, which borders the city’s northern edge. The lake is both unusually shallow — rarely more than 20 feet deep — and unusually large -— more than half the size of the state of Rhode Island. A 20-foot storm surge arriving in concert with both high tide and 20-inch rains could overwhelm the city’s more vulnerable lakeside levees and then flow downhill all the way to the French Quarter. Many of the city’s massive drainage pumps are located closer to the lake. Were they to be flooded out, the city would not only be helplessly inundated while the hurricane is overhead— it would remain so for weeks if not months.”

Those of us from Louisiana and the Gulf Coast remember another high-powered lady that tromped ashore pushing a 20-foot storm surge. In 1969 Camille (an even stronger storm) made landfall within 50 miles of where Katrina came ashore. While Camille was a deadly storm claiming 250 lives along the coast and another 100 or so due to inland flooding, especially in Virginia, she didn’t wreak the havoc of Katrina. Camille was a bit more compact than Katrina — a 10-mile eye compared to 32-miles for Katrina, and she took a more easterly route.

While these factors surely made a difference with regards to the impact on New Orleans, there is another factor to consider. Ringle points to it in his column; “[New Orleans] was long protected by scores of miles of surrounding saltwater marshes capable of sponging up even massive storm surges like a swampy dishrag.

For the last half of the 20th century and into the present day, those wetlands have been disappearing — hundreds of acres of them every year — starved by levees from the Mississippi River, overflows that once fed them with silt from Minnesota and Iowa and Missouri, and eroded by canals dug for oil exploration and suburban subdivisions.”

The marshes and wetlands of South Louisiana have been disappearing at an unbelievable rate since the 1930s. It is estimated that coastal Louisiana lost nearly 2,000 square miles of land between 1932 and 2000. In a Discovery News piece, Gregory Steyer, an ecologist for the USGS National Wetlands Research Center in Louisiana, compared these wetlands to a car bumper, noting that they absorb some of the initial impact from storms such as Katrina. Scientists believe that storm surges are reduced by one foot for every three miles of wetlands/marsh.

Because of the shrinking Louisiana coastline, the Gulf of Mexico is 20 miles closer to New Orleans than it was when Camille visited. Those 20 miles could have absorbed seven feet of storm surge.

From the beginning of time there has been a give and take along the Gulf Coast with Ol’ Man River depositing silt and the gulf lapping it away. This was a pretty stable ecosystem as far as net gains and losses were concerned but uneven in distribution. The Mississippi was always wandering back and forth seeking the path of least resistance. I remember growing up in northeastern Louisiana fishing the many oxbow lakes created by this meandering.

The meandering and natural seasonal flooding of rivers like the Mississippi don’t sit well with a species intent on permanent residency. After the great flood of 1927, man went to work corralling Ol’ Man River with channelization and a system of dams and levees. Wetlands first became farmlands then farmlands became suburbs — then black gold.

One need only look about 50 miles southwest of New Orleans to see the impacts of oil and gas exploration and extraction on coastal wetlands. Terrebonne Parish, which is nearly 90 percent wetlands, ranks first in natural gas production and third in oil production in Louisiana. It also ranks first in the loss of wetlands.

Next week we will discuss more about the science and politics of restoring Louisiana’s coastal wetlands.

(Don Hendershot can be reached at ddihen@earthlink.net.)