Recent morphological evolution of the Lower Mississippi River (original) (raw)

Abstract

This study documents slope and stream power changes in the Lower Mississippi River during the pre-cutoff 1880s-. Ž. 1930s , and post-cutoff 1943-1992 periods. The study reach extends from New Madrid, MO, to Natchez, MS, a distance of about 900 km. Analyses for six major reaches and 13 sub-reaches for the pre-and post-cutoff periods indicate that the river presently has a much larger slope and stream power than prior to the cutoffs. The largest increases have occurred between Fulton, TN, and Lake Providence, LA, where slope and stream power increases range from about 27% to 36% and 20% to 38%, respectively. Increases in slope and stream power in reaches upstream and downstream have also occurred, but to a lesser degree. Previous investigations have shown that no coarsening of the bed material has occurred since 1932, and that the bed material may actually be somewhat finer overall. As the Lower Mississippi River is not a sediment-starved system, an increase in stream power with no change in D would be expected to be offset by an increase in the bed material 50 load as the river adjusts towards equilibrium. Previous investigators have inferred a reduction in the sediment loads on the Mississippi River this century based on analyses of total measured suspended loads. However, these results should be viewed as primarily representing the changes in wash load and should not be taken to imply that bed material loads have also decreased. Therefore, the bed material loads in the study reach should be greater than in the pre-cutoff period. Excess stream power in the sub-reaches directly affected by cutoffs resulted in scour that increased downstream bed material load. These elevated sediment loads play a key role in driving morphological adjustments towards equilibrium in the post-cutoff channel. The stability status of the channel in the study reach currently ranges from dynamic equilibrium in the farthest upstream reaches through severe degradation to dynamic equilibrium in the middle reaches, and aggradation in the lowest reaches. These evolutionary trends cannot be explained by consideration of changes in slope and stream power alone. Changes in the incoming bed material load to each reach generated by upstream channel evolution must also be considered.

Loading...

Loading Preview

Sorry, preview is currently unavailable. You can download the paper by clicking the button above.

References (32)

  1. ASCE Sedimentation Task Committee, 1977. Sedimentation Engi- neering. American Society of Civil Engineers, New York.
  2. Bagnold, R. A., 1966. An approach to the sediment transport problem from general physics. Professional Paper 4221, United States Geological Survey, Reston, VA.
  3. Biedenharn, D.S., 1995. Lower Mississippi River Channel Re- sponse: Past, Present and Future. Ph.D. Dissertation, Depart- ment of Civil Engineering, Colorado State University, Fort Collins, CO.
  4. Biedenharn, D.S., Thorne, C.R., 1994. Magnitude-frequency analysis of sediment transport in the Lower Mississippi River. Regul. Rivers: Res. Manage. 9, 237-251.
  5. Biedenharn, D.S., Watson, C.C., 1997. Stage adjustment in the Lower Mississippi River. Regul. Rivers: Res. Manage. 13, 517-536.
  6. Dardeau, E.A., Causey, E.M., 1990. Downward trend in Missis- sippi River suspended-sediment loads. Potamology Program Report 5, Environmental Laboratory, US Army Engineer Wa- terways Experiment Station, Vicksburg, MS, USA.
  7. Elliott, C.M., Rentschler, R.R., Brooks, J.H., 1991. Response of the Lower Mississippi River low-flow stages. Proceedings of the Fifth U.S. Interagency Sedimentation Conference, Las Vegas, NE. Vol. 1, pp. 4-164-4-23.
  8. Ferguson, H.B., 1940. History of the improvement of the Lower Mississippi River for flood control and navigation, 1932-1939. Print 500, 1-40, Mississippi River Commission, Vicksburg, MS. Keown, M.P., Dardeau, E.A., Causey, E.M., 1981. Characteriza- tion of the suspended sediment regime and bed material gradation of the Mississippi River Basin. Potamology Pro- Ž . gramme P-1 Report 1, Vols. 1 and 2, U.S. Army Corps of Engineer WES, Vicksburg, MS.
  9. Kesel, R.H., 1988. The decline in sediment load of the Lower Mississippi River and its influence on adjacent wetlands. Ž . Environ. Geol. Water Sci. 11 3 , 271-281.
  10. Kleinbaum, D., Kupper, G., Muller, L., 1988. Applied Regression Analysis and Other Multivariable Methods. Wadsworth Pub- lishing, Belmont, CA.
  11. Knighton, D., 1998. Fluvial Form and Processes. Wiley, New York, NY.
  12. Lane, E.W., 1947. The effect of cutting off bends in rivers. University of Iowa Studies in Engineering. Proceedings of the Third Hydraulics Conference, Bulletin 31, University of Iowa, Iowa City, Iowa, pp. 239-240.
  13. Lane, E.W., 1955. The importance of fluvial morphology in hydraulic engineering. Proc. Am. Soc. Civ. Eng. 81, Separate No. 745.
  14. Leopold, L.B., Bull, W.B., 1979. Base level, aggradation and grade. Proc. Am. Philos. Soc. 123, 168-202.
  15. Mackin, J.H., 1948. Concept of the graded river. Bull. Geol. Soc. Am. 59, 463-512.
  16. Madden, E.B., 1974. Mississippi River and Tributaries Project, Problems Relating to Changes in Hydraulic Capacity of the Mississippi River. TR No. 12, U.S. Army Corps of Engineers, Committee on Channel Stabilization, Vicksburg, MS.
  17. Nordin, C.F., Queen, B.S., 1992. Particle size distributions of bed sediments along the thalweg of the Mississippi River, Cairo, Illinois, to Head of Passes, September 1989. Potamology Ž .
  18. Program P-1 , Report 7, U.S. Army Corps of Engineers, Lower Mississippi Valley Division Office, Vicksburg, MS.
  19. Richards, K., 1982. Rivers, Form and Process in Alluvial Chan- nels. Metheun & Co., New York, NY.
  20. Robbins, L.G., 1977. Suspended sediment and bed material stud- ies on the Lower Mississippi River. Potamology Investigation Report 300-1, U.S. Army Corps of Engineers, Vicksburg District, Vicksburg, MS.
  21. Schumm, S.A., Parker, R.S., 1973. Implications of complex re- sponse of drainage systems for Quaternary alluvial stratigra- phy. Nat. Phys. Sci. 243, 99-100.
  22. Schumm, S.A., Harvey, M.D., Watson, C.C., 1984. Incised Chan- nels, Morphology, Dynamics and Control. Water Resources Publication, Littleton, CO.
  23. Schumm, S.A., Rutherfurd, I.D., Brooks, J., 1994. Pre-cutoff morphology of the Lower Mississippi River. In: Schumm, S., Ž .
  24. Winkley, A. Eds. , The Variability of Large Alluvial Rivers. American Society of Civil Engineers, New York, NY, pp. 13-44.
  25. Simon, A., Thorne, C.R, 1996. Channel adjustment of an unstable coarse-grained stream: opposing trends of boundary and criti- cal shear stress and the applicability of extremal hypotheses. Earth Surf. Proc. Landforms 21, 155-180.
  26. Stanley Consultants, 1990. Lower Mississippi River Hydraulic Ž . Studies 1950-1988 River Mile 320 to 596 . U.S. Army Corps of Engineers, Vicksburg District, Vicksburg, MS.
  27. D.S. Biedenharn et al.r Geomorphology 34 2000 227-249
  28. U.S. Army Corps of Engineers, 1962. Report on re-examination of Mississippi river channel alignment for stabilization. Missis- sippi River Commission, Vicksburg, MS.
  29. U.S. Army Corps of Engineers, 1982. Analysis of major parame- ters affecting the behavior of the Mississippi River. Missis- Ž . sippi River Commission, Potamology Program P-1 , Report 4, Vicksburg, MS.
  30. Winkley, B.R., 1977. Man-made cutoffs on the Lower Mississippi River, conception, construction and river response. U.S. Army Engineer District, Vicksburg Potamology Investigations Re- port 300-2, Vicksburg, MS.
  31. Winkley, B.R., 1994. Response of the Lower Mississippi River to flood control and navigation improvements. In: Schumm, S., Ž .
  32. Winkley, A. Eds. , The Variability of Large Alluvial Rivers. American Society of Civil Engineers, New York, NY, pp. 45-74.