Sunday, April 24, 2011

Louisiana's Salt Marshes

We continued our drive along LA 82 (the Creole Nature Trail) through the Louisiana Outback after leaving the Cameron Prairie National Wildlife Refuge.

When we reached the east-west section of route 82, we headed east through an area called the Lower Mermentau Basin. This area is comprised of two sub-basins: the Lakes Sub-basin, located
immediately south of the limit of the coastal zone and north of LA 82, and the Chenier Sub-basin, which lies between Louisiana Highway 82 and the Gulf of Mexico.

Taking photos as we traveled along this highway that divided the two sub-basins, we were always between 4 and 7 miles north of the Gulf. This area, like the entire coast of Louisiana, is occupied by extensive salt marshes, which grade into brackish marshes, then into freshwater marsh in the upper Mississippi River delta.

These salt marshes are extremely important to southern Louisiana. "In the past, the Mississippi River was free to go where it wanted; it wandered all over the map, changing its course entirely from time to time.
In colonial times, when the Mississippi neared the Gulf it widened and slowed, forming a series of wide loops or meanders. As it slowed down, it began to drop the great load of sediment accumulated during its long journey. These sediments were deposited in the shallow offshore waters of the Gulf. Much of that sediment was trapped by the coastal marshes. After building up a vast delta, the River would eventually find a new channel, and start to build up yet another delta.

"But now the river has been tamed and channeled between narrow banks by the Army Corps. When you force a fluid into a narrower channel, you increase its flow rate. Water shoots out the mouth of the River, and all that fertile topsoil from the Midwest now goes hurtling out over the edge of the continental shelf. Very little is retained in the coastal marshes. And the delta, deprived of these sediments, is being steadily eroded.

"Add to this, the damage caused by extensive canals cut by the oil industry and the result is that Southern Louisiana is literally being nibbled to death by the Gulf. Forty square miles per year of Louisiana vanishes into the Gulf every year. At that rate, within 100 years all of Terrebonne Parish will have disappeared beneath the waves. New Orleans will be well on its way to being a seaport, probably another Venice!" (louisiana salt marshes web page).

The coastal marshes now stand as our only buffer against the tremendous forces of wind and water from hurricanes from the Gulf.

Because of the risk of a storm surge from a hurricane, homes along the highway are required to be built either on a berm (above) or stilts (left). Those built on berms must wait two years for the berm to become established before they can build on it.

Some local residents choose to deal with this ever-present danger of hurricanes by employing humor. This "Cajun Hi-Rise," like other mobile homes similarly mounted on stilts, can withstand strong winds better than the typical stick-built home.

Shortly after passing through the small town of Pelican Island, we headed north.

En route, we crossed the Schooner Bayou Canal, which connected White Lake and Vermilion Bay, on our way to Abbeville and, finally, back to our base in Duson, LA.

A few days later found us on the eastern side of Vermilion Bay in Cypremort Point State Park.

The Park had a few picnic tables in the open and about a half dozen tables covered with these unusual frame supports.

There is a half-mile man-made beach in the park. Beyond the boundary of the swimming area, we could see an oil platform in Vermilion Bay.

Although it was cool and windy, some young folks neverthe-less were testing the waters.

On our way out of the park, we passed these fellows checking over their shrimp boat.

Then it was on to the town of Cypremort Point. We'll have some photos in a couple of days.

1 comment:

Respectful Empiricist said...

While researching salt marshes Google sent me to your blog. I know you posted this 6 months ago but I still thought to let you know I enjoyed your thoughts and photographs.

Mike Stahl (