9313688 Furbish This project is aimed at providing a general description of the complex flow fields that can occur in steep mountain streams, whose morphologies consist of irregular arrangements of stable boulders and logs, and small gravel bars. The treatment makes use of both linear and nonlinear formulations involving depth-integrated equations of momentum and mass continuity to describe how streamwise and transverse flow velocities, and water-surface topography, respond to an irregular bed whose topography is significantly more complex than that of alluvial self-formed channels. The work is an extension of a linear model which predicts that the wavelength of nascent bend forms can be longer than that of the dominant bendforms. Theoretical aspects of the work will be tested with data collected rom North Boulder Creek, Colorado. Data will come from a single reach of nearly 80 channel widths in length, and from two short reaches selected for detailed measurements of bed topography and flow. Results will provide a mechanical basis for testing the idea that these bouldery channels can undergo a self-stabilizing period that involves an interaction among extant flow conditions, variable erodibility of bed and bank materials, local armoring of the bed, and piecemeal transport of sediment.
