The Vanishing Coast

wetlands over time

http://microbewiki.kenyon.edu/index.php/Wetlands

By Sarah Patterson

Louisiana’s most notable yet devastating story is Hurricane Katrina. The hurricane dislocated millions of people and deeply impacted the Louisiana landscape. After the Hurricane, there became an increased awareness of Louisiana’s diminishing coast and wetlands. In the paper Restoring the Sustainability of the Mississippi River Delta, Paul Kemp, John Day and Angelina Freeman say that “after the storms, wetland restoration was increasingly regarded as an integral, but long neglected…” part of storm protection. They discuss the 2012 Master Plan to replenish and rebuild the Louisiana coast and wetlands.

The Mississippi River drains almost 40 percent of the US river basins. The average discharge from the Mississippi is 19000 cubic meters per second or 19 million liters. To put this in perspective this is approximately 9.5 million two liter coke bottles. This discharge carries sediment down through the Mississippi and forms the deltas and the wetlands along the Louisiana cost. Man’s intervention with structural equipment such as dams and levees on the Mississippi has almost completely separated the river with the deltas along the coast. This has caused sediment discharge to drop approximately 50 percent. Combined with the rise in sea level, dredged canals, and other man made structures, the Louisiana wetlands are disappearing into open water. The Master Plan predicts 386 – 772 square miles of wetland loss over the next 50 years with no restoration. That would be like losing wetlands the size of Lake Pontchartrain, which is 629 square miles.

The 2010 Master Plan put out by the Louisiana Coastal Protection and Restoration Authority proposes three ways to restore the land. First, reconnecting the Mississippi River with the delta, next, pumping of dredged sediment to rebuild barrier islands, and finally, replenishing unnecessary canals.

Since the separation of the Mississippi River from its Delta after the 1927 flood, the wetlands have been disappearing. The plan to fix this is to discharge a large amount of water and sediment in specific areas. After 20 years of sediment diversion, it is estimated that the river delta will begin to gain land. The energy used to produce these diversions is “front-loaded”, or using most of the energy in the initial startup of the project. After the start up, the most important energy that will be utilized is gravity. Although the cost of this at first will be expensive, it is necessary that these deltas be reconnected to the river, and the wetlands are replenished.

The other way to replenish wetlands and barrier islands is through pumping dredged sediment into the wetlands. Through this method land is created almost instantaneously, which is helpful for flood protection and for building up the wetlands. Pumping sediment can also reach places that diversions cannot. This technique is used to build up barrier islands to protect the coast from storm surges from hurricanes.  This way estuaries and fishing volume is not affected because the amount of water that is used is minimal. According to John Day and Paul Kemp, who are professors at LSU in the Oceanography and Costal Sciences Department, this restoration technique’s “advantages, in some cases, may outweigh cost considerations”. Although dredging sediment may be more expensive per acre than diversions, the benefits of being able to control and schedule land building outweigh the costs.

When canals where dredged for oil and gas lines, logging boats, and shipping boats, they allowed an influx of saltwater into the fresh water marshes. This destroyed many of the plants and some of the wetlands have disappeared into open water. One of the goals of the master plan is to replenish these canals, especially the ones that are no longer in use or unnecessarily large. This will keep salt water from rising into the fresh water marshes and preserve more land.

“Operating the 80 year old MR&T [Mississippi River & Tributaries] project as originally conceived is becoming increasingly unaffordable, while its negative side effects are becoming ever more apparent” John Day, Paul Kemp, and Angelia Freeman exclaim. If we continue with the old system of levees, dams, dredging canals, and ignore the disappearing coast. Louisiana will no longer be the state that we know it today. Land, homes, and history will be lost, never to be replenished again.

Day, John W., Paul Kemp, and Angelina M. Freeman. “Restoring the Sustainability of the Mississippi River Delta.” Ecological Engineering65 (2014): 131-46. Science Direct. 23 Oct. 2013. Web. 11 Sept. 2014.

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