The multi-purpose permutation procedures (MRPP) test statistic is designed to analyze multivariate data at the ordinal or higher levels. It is based on the weighted averages of symmetric distance functions over all paired objects within a priori disjoint groups of objects from a finite population of objects where each object's response is a point in an r-dimensional space. Thus, the arguments of each r-dimensional point correspond to the r measured responses of each object in the finite population of objects. The null hypothesis underlying MRPP is that the observed sample of objects within groups of a specified size structure is randomly obtained from the pooled collection of objects comprising the finite population. The procedure is used to test the presumed geomorphic differences among three reaches of the Lower Mississippi River. A combination of the proposed reaches is favored and several variable-based reach configurations are proposed. ?? 1993 International Association for Mathernatical Geology.