Flow Structure in Steep Mountain Streams

该项目旨在对陡峭的山间溪流中可能出现的复杂流场进行一般描述，其形态由不规则排列的稳定巨石和原木以及小砾石条组成。该处理方法利用线性和非线性公式，包括动量和质量连续性的深度积分方程，来描述水流方向和横向流速以及水面地形对不规则河床的响应，这种河床的地形比冲积自形成的河道复杂得多。这项工作是一个线性模型的扩展，该模型预测新生弯曲形式的波长可以比主要弯曲形式的波长长。这项工作的理论方面将用从科罗拉多州北博尔德溪收集的数据进行测试。数据将来自近80个通道宽度的单一河段，以及为详细测量河床地形和水流而选择的两个短河段。研究结果将为验证这样一种观点提供一个力学基础，即这些砾质河道可以经历一个自稳定期，其中包括现有水流条件、河床和河岸物质的可变可蚀性、河床的局部装甲和沉积物的碎片运输之间的相互作用。

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.