Remarkable Rivers
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A view of the leveed Mississippi River running through Plaquemine Parish. |
Louisiana has many extraordinary river systems. The state's larger rivers are the Mississippi, Atchafalaya, Red, Black, Sabine, Ouachita, Mermentau, and Calcasieu. These streams support amazingly diverse fish populations and hold great scenic value. The Louisiana Department of Wildlife and Fisheries has a program called the BIG RIVER PROGRAM whereby scientists are collecting data on the different species of fish in these varied waterway habitats. Did you know that 84 different species of fish were collected by biologists in just a few weeks time in the Mississippi and Atchafalaya rivers alone? Since Bald Eagles like to feast on fish, it is no wonder CC and I have recently seen that bird every few miles the last three weeks!
The Mississippi and the Atchafalaya rivers are wide, muddy, and oh, so busy with traffic. Cruising on these waterways is an awesome experience. We are presently near the Atchafalaya River in the Morgan City area. The last place we parked the Wetland Wanderer was on Bayou Teche. The wide high ground on both sides of the Teche is a reminder of the extraordinary land creating ability of the Mississippi River. We parked at a home, which backed up to this now lazy bayou that used to be the raging Mississippi River.
The Mississippi River system is one of the most studied and monitored in the world. Our planet is about 4.65 billion years old, and over the eons natural forces have constantly changed its surface. The processes that created all of our coastal wetlands east of Lafayette took only about 7,000 years--an extremely short period compared to the billions of years of geologic time. The story of the formation of the Mississippi River deltas east of Lafayette is one of dynamic action! The 2,340-mile long, sediment carrying Mississippi River creates a delta by sediment deposition when it slows down as it approaches its final destination, the Gulf of Mexico. A good comparison is a dirt-water mixture in an electric blender. When the blender blades spin very fast, all of the dirt particles stay suspended, and none of them settle out to the bottom. If you reduce the water turbulence by switching to the slowest spin speed of the blades, some of the larger dirt particles will soon settle out to the bottom. The same thing happens to the sediment that is carried by a river that is slowed down.
The river prefers the easiest and shortest route into the Gulf. Over time, water flow in a river channel is slowed by sediment deposits in the waterway that create sandbars and islands which resist the flow of water. Eventually, a channel becomes so troublesome that the river spills over one bank or the other and starts to seek a new shorter and less hindered route to its destination. The river leaves behind deposited sediment of the previous channel. This deposited sand, silt, and clay make a new strip of high and well drained land many miles wide. As these abandoned old river channels age, they become much narrower; that happened to Bayou Teche. It was once the main channel of the Mississippi, it is now a peaceful, lazy bayou with homes and camps along its edges.
Over the past several thousands of years, a series of deltas were created. The Mississippi changed channels five to seven times trying to reach the Gulf in a hurry. Listed below are the names of five important deltas.
Cocodrie- 2600 B.C. to 1800 B.C.
Teche- 1900 B.C. to 700 B.C.
St. Bernard- 600 B.C. to 300 B.C.
Lafourche- A.D. 65- A.D. 1300
Modern- A. D. 900- present
These deltas originally extended from 15 to 50 miles out into the Gulf! For example, the Chandeleur Island chain off eastern coastal Louisiana is all that remains of the outer rim of the original St. Bernard delta.
The forces of nature that create mountains, great rivers, and canyons are indeed dramatic. Floods have created some of the world's most extensive and fertile farmland by depositing rich layers of sediment on wide floodplains. The Nile River delta of Africa is a classic example. The Mississippi deltas have Louisiana's most fertile soils. Therefore, many people settled in a delta region to raise fast growing crops and live. Naturally occurring floods are as harmful to humans as levees and canals are to a river system. As towns and cities sprang up, early settlers understandably began trying to control the river's flooding to stop damage to crops and homes. The first levee was built in New Orleans in 1718.
Modern levees reduce the hazard of flooding and make the delta high ground more livable. However, without the normal spring flooding and sediment deposits of the river the wetlands ecosystem is completely altered. Modern levees have turned the meandering Mississippi into a fast flowing water chute. If you have ever been on a water slide you can understand. Your body gets going really fast when you are surrounded by close barriers on two sides, and you have only a narrow path to travel. The sediment in the river goes fast too, and like you speeding into the deep pool at the slide's end, the sediment winds up way offshore and settles in the deeper Gulf waters. Marshes and barrier islands that protect the coastline from hurricane wave damage are no longer being built up by the river. Freshwater marshes are no longer being nourished by river fresh water and nutrient rich sediment.
Flood control levees, shipping canals, oil and gas canals all benefit human society but they stop the river's natural ability to build and protect land. As you see, what makes solving the problem of Louisiana's wetland loss so complicated is trying to find the balance between control of a mighty river for property and safety and letting mother nature do her work!
Toward the middle of the 1900s the almost 1,000 year old channel of the Mississippi River below the Atchafalaya River became quite curvy and long. The Atchafalaya River, with its straight and relatively short route to the Gulf, is the course that many think the Mississippi River would have changed to a few decades ago had it not been for man's building a water control structure at the junction of the two rivers.
We are now in the Atchafalaya Basin. As a distributary, the Atchafalaya River is allowed to take up to 1/3 of the Mississippi's flow and sediment load to the Gulf of Mexico. Despite the alarming rate of Louisiana's coastal wetland loss, the delta being created at the mouth of the Atchafalaya River is the fastest growing delta in the world! A very bright spot in the overall bleak outlook for out state's wetlands. In the short distance C.C. and I have traveled we have become increasingly aware of the great diversity of wetland habitats and how complicated maintaining those environments will be.
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