REACH CLASSIFICATIONS OF THE LOWER MISSISSIPPI-RIVER

A classification of the lower Mississippi River into geomorphically di stinct reaches provides an effective framework within which the influe nce of numerous morphologic variables can be analyzed. A singular real ization of the river, however, requires that a statistical inference b e applied to the results which provides a level of assurance to the co nclusions. A nonparametric method, Multi-Response Permutation Procedur es (MRPP), is employed to evaluate the significance of channel morphol ogy variables within an a priori reach classification based upon sinuo sity and valley slope. An alternative classification is proffered, gen erated by MRPP, which defines homogeneous subpopulations of the river as reaches for the collective response of the channel morphology varia bles. The numeric analyses generate a refinement, by further subdivisi on, of the original proposed reach structure. Within each reach the mu ltivariate response of the system can be studied through space and tim e. Within the time period considered here, 1880 to 1915, the river cha nnel became progressively wider and shallower. These trends are spatia lly manifest in fewer longer reaches in 1880 and more shorter reaches in 1915. This increased variability is concentrated in the areas affec ted by the Lake County and Monroe uplifts.