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|Title:||Analysis of major parameters affecting the behavior of the Mississippi River|
|Authors:||United States. Mississippi River Commission.|
United States. Army. Corps of Engineers. Lower Mississippi Valley Division.
Tuttle, James R.
|Publisher:||U.S. Army Engineer Waterways Experiment Station.|
Engineer Research and Development Center (U.S.)
|Series/Report no.:||Report (Potamology Program--P-1 (U.S.)) ; 4.|
Abstract: The present potamology program was initiated after the major flood of 1973, which confirmed that significant flood control capacity had been lost over a major portion of the lower Mississippi River. Objectives of the program are to obtain a better understanding of: the river's reaction to various arameters, why these reactions occur, and how to control these reactions and/or predict future changes resulting from them. The studies described in this report consisted of detailed investigation of four major parameters: hydrology, sedimentation, channel geometry, and man-made modifications. Hydrology of the Mississippi River is highly variable. Stages change daily, seasonally, and annually. These changes in stage continuously influence scour and fill patterns along the channel bed as well as the magnitude of hydraulic roughness, two variables that significantly affect the capacity of the channel to transport flow. It is important, therefore, that the effects of variable hydrology be recognized and understood and that flood control and channel improvement structures be designed and constructed to accommodate what nature provides. Sediments are very important because they can accumulate in a manner that can seriously affect flood control capacity and navigation conditions. The most important sediments are those transported on and near the channel bed. The majority of these materials appear to be transported by a process called "trading" whereby material is scoured from one location, generally deep pools and point bars, and deposited at a location farther downstream, usually in crossings, during rising stages with the process reversing itself during falling stages. Channel geometry and alignment of the Mississippi River are extremely variable. This discontinuity affects the capability of the channel to effectively transport flow and sediment, causing conditions that can affect flood flow lines and interfere with navigation. Man-made modifications (levees, cutoffs, revetments, and dikes) have individually and collectively influenced river behavior. Some reaches of the river, although improved, continue to be problem areas in spite of considerable construction effort. It appears that present design concepts and criteria are generally adequate except in the more difficult reaches where development of alternative design concepts is needed. Of the four parameters studied, effective management of the sediment parameter offers the greatest potential toward achievement of a stable, dependable channel for both flood control and navigation. The second most significant parameter, one interrelated with sediment transport and storage, is channel geometry and alignment. Future potamology programs should focus primarily on the major objective of improving the balance between hydraulic parameters and sediment transport capabilities for a full range of flows, locally and throughout the middle and lower Mississippi River.
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