1. When rivers go over their banks, the spreading water immediately slows up, dr
ID: 291678 • Letter: 1
Question
1.
When rivers go over their banks, the spreading water immediately slows up, dropping the heavier sediments. The finer the silt, the farther it is scattered, but so much falls close to the river that natural levees rise through time. The first houses of New Orleans were built on the natural levees, overlooking the river. In the face of disaster, there was no better place to go. If there was to be a New Orleans, the levees themselves would have to be raised, and the owners of the houses were ordered to do the raising.
The Mississippi River, with its sand and silt, has created most of Louisiana, and it could not have done so by remaining in one channel. If it had, southern Louisiana would be a long narrow peninsula reaching into the Gulf of Mexico. Southern Louisiana exists in its present form because the Mississippi River has jumped here and there within an arc about two hundred miles wide, like a pianist playing with one hand—frequently and radically changing course, surging over the left or the right bank to go off in utterly new directions. Always it is the river’s purpose to get to the Gulf by the shortest and steepest gradient. As the mouth advances southward and the river lengthens, the gradient declines, the current slows, and sediment builds up the bed. Eventually, it builds up so much that the river spills to one side. Major shifts of that nature have tended to occur roughly once a millennium. The Mississippi’s main channel of three thousand years ago is now the quiet water of Bayou Teche, which mimics the shape of the Mississippi. Along Bayou Teche, on the high ground of ancient natural levees, are Jeanerette, Breaux Bridge, Broussard, Olivier—arcuate strings of Cajun towns. Eight hundred years before the birth of Christ, the channel was captured from the east. It shifted abruptly and flowed in that direction for about a thousand years. In the second century A.D., it was captured again, and taken south, by the now unprepossessing Bayou Lafourche, which, by the year 1000, was losing its hegemony to the river’s present course, through the region that would be known as Plaquemines. By the nineteen-fifties, the Mississippi River had advanced so far past New Orleans and out into the Gulf that it was about to shift again, and its offspring Atchafalaya was ready to receive it. By the route of the Atchafalaya, the distance across the delta plain was a hundred and forty-five miles—well under half the length of the route of the master stream.
2. Fluvial Processes and landforms
What is the relationship between the two paragraphs and Fluvial Processes and landforms
Explanation / Answer
The two paragraphs depict the importance of the river erosion and the landforms created by the erosional and depositional work of the fluvial processes.The heavier the material is the near it is dropped whereas the finer silt carried by the river water is deposited at more distance.
The Natural levees are the depositional features created by the river deposition due to the dropping of it's load,These Natural levees are used for settlement purpose one such example is New Orleans .The parapgraphs also shows the landforms created by the depositional work of the rivers like The Mississippi River, with the load it carries like sand and silt, Louisiana is the result of such a work.
There are many significant landforms created by the erosional work resulting from fluvial erosion by streams that includes river valleys,waterfalls,rapids and the depositional features such as Alluvial fans and Cones,Natural levees which is infact a narrow belt of ridges of low height built by the process of deposition of sediments because of the spilt water of the stream or rivers on either it;s banks,Delta etc.The paragraphs had mostly depicted levees that are created during the floods when water overtops the banks of the rivers and hence spreads over the adjoining areas.
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