A PRELIMINARY APPROACH TO PROCESS-BASED STREAM CLASSIFICATION IN THE CRITICAL ZONE: THE TEXAS EXAMPLE

Stream networks serve as pathways for transport of energy and mass through the critical zone by connecting the top of the canopy to the bottom of the aquifer. Thus, a stream can be viewed as a continuum. Because streams serve a fundamental role in landscape development, researchers have attempted various classifications. Prior classification systems have run the gamut of scale-dependent perspectives ranging from watershed to reach. Classification schemes have included stream ordering, stream pattern, erosion-transport-deposition reach system, and reach pattern. None of these systems have received universal acceptance. We are looking for river patterns in the critical zone that can be organized by characteristics and thus categorized, which can help understand fundamental underlying thresholds and linkages. This type of classification approach identifies similarities and differences between and among various streams and leads to a better understanding of the structure of streams within the critical zone.

A critical zone stream classification system has to account for the fundamental characteristics of erosion, transportation, and deposition. A process-based systems' approach to stream classification within the critical zone allows the inclusion of the geomorphic concepts of equilibrium, magnitude, frequency, scale, and process-linkage, thresholds that control erosion, runoff, geochemical characteristics of water, and anthropogenic influences. A stream classification system based on stream morphology provides a common ground for understanding stream conditions and potentials in vastly differing settings, provides a consistent frame of reference, facilitates prediction of stream activity from appearance, and provides a view of the health of a stream for restoration. This research focuses on the variables of climate, geology, and stream gradient that influence stream morphology within the various physiographic provinces of Texas. Spatial statistics reveal potential grouping of patterns of curvature within the various rivers of Texas based on the variables observed. A preliminary stream classification for specific physiographic locations can be very useful for providing an understanding of river behavior related to specific physiographic provinces.