Gravel transport over low-water crossings in Johnson Fork River, Texas.

摘要

This study is part of the TxDOT project 0-4695 "Guidance for Design in Areas of Extreme Bed-load Mobility." Low-water crossings are commonly used on low-traffic-volume stream crossings in the Hill Country of central Texas. This thesis summarizes and presents information, understanding, and conclusion of the first two years of preliminary or reconnaissance research, and does not provide a complete solution for TxDOT to solve sediment deposition problems related to low-water crossings yet. This study includes extensive literature review, field visit of three low-water crossings in Johnson Fork River, field data collection in determining particle size distribution upstream and downstream sides of the crossings, preliminary flow simulation by using HEC-RAS software, and bedload transport rate estimated by using BAGS (Bedload Assessment in Gravel-bedded Streams) and Bagnold's equation related to stream power. It was concluded from this study that significant gravel transport can take place when the flow is still subcritical. (Abstract shortened by UMI.)