Non-linear interactions among river channels and the water and sediment they convey result in a broad spectrum of process and form across a range of spatial and temporal scales. Attempts to distill this complexity have long been stymied by the non-uniform conditions found in natural rivers and by the dual role of channel morphology as both a consequence of and a control on flow and sediment transport processes. Similarly, traditional approaches emphasizing the prediction of cross-sectional averages have not addressed two-dimensional spatial variations of depth and velocity within and among reaches, despite their fundamental role in the relationship between channel morphology and sediment transport. Efforts to characterize and model these important interactions have been hindered by the difficulty of measuring channel and floodplain topography with sufficient precision and economy. The goals of this doctoral dissertation research are to: develop remote sensing and geostatistical methods for characterizing spatial patterns of river morphology and hydraulics; apply these techniques to a pristine watershed in Yellowstone National Park; and relate the observed patterns of topography and flow to sediment transport and channel change. The technical innovations resulting from this study include a flexible, physics-based approach to remote sensing of rivers and a specialized geostatistical framework for obtaining improved representations of channel form and quantitative descriptions of reach-scale spatial structure. The field component of the project involves detailed topographic surveys and spatially distributed measurements of flow depth and velocity and bed material grain size in several stream reaches at a range of discharges. To provide context for these intensive field sites, a time series of remotely sensed data spanning the period from 1949 to 2004 will be used to map variations in water depth, document changes in channel planform and valley floor land cover, and estimate long-term rates of sediment transfer.
This project will introduce a new, distinctly spatial perspective that will allow geomorphic theory to move beyond one-dimensional prediction of mean depths and velocities for individual cross-sections to parametric modeling of the variability and spatial pattern of these hydraulic quantities. The techniques developed will also facilitate examination of the relationship between channel morphology and sediment transport across an expanded range of scales. These tools will be particularly useful for river restoration, where effective monitoring and adaptive management are critical to project success but are often compromised by the difficulty of collecting even basic field data and by the lack of objective criteria for assessing progress toward such nebulous goals as "increased geomorphic complexity.'"
