Patterns of variation in a fluvial system

Sixteen hydromorphic variables, with observations grouped by stream order, were subjected to principal components analysis to investigate the manner in which variables interact in a downstream direction within a drainage basin. The degree of intercorrelation between variables in a fluvial system is influenced by geology, structure, and variation in the physical characteristics of stream basins. The contention here is that since the degree to which these factors are effective varies downstream in an orderly way, the intensity of interaction between variables should also be so ordered. The results of the analysis support this because the variance accounted for by the first and second principal components increased systematically downstream, whereas that associated with principal components three through six generally decreased. The structure of the data is also examined in the context of varimax rotated components, and the changes that occur between lower- and higher-order stream basins are identified.