Flow Structure in Steep Mountain Streams

9313688 FURBISH本项目旨在对陡峭的山溪中可能出现的复杂流场进行概括性的描述，山溪的形态由稳定的巨石和原木以及小砾石栏组成的不规则排列。该方法利用动量和质量连续的深度积分方程的线性和非线性公式来描述水流速度、横向水流速度以及水面地形对不规则河床的响应，而不规则河床的地形明显比冲积自形成河道复杂得多。这项工作是一个线性模型的扩展，该模型预测新形成的弯曲形式的波长可能比主要弯曲形式的波长更长。这项工作的理论方面将用从科罗拉多州北博尔德克里克收集的数据进行测试。数据将来自长度近80个航道宽度的单一河段，以及为详细测量河床地形和水流而选择的两个短河段。这些结果将为检验这些砾石渠道可以经历一个自稳期的想法提供一个力学基础，该稳定期涉及现有水流条件、河床和河岸物质的可变侵蚀性、河床的局部装甲和泥沙的零碎输送之间的相互作用。

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.