Development of Design Methods for In-Stream Flow Control Structures National Cooperative Highway Research Program (NCHRP) Report 795.

摘要

Natural resource agencies have encouraged many state DOTs to use natural (context-sensitive) stream stability and restoration measures in lieu of traditional engineering responses to stabilize rivers and streams against erosion and scour. These measures include the construction of shallow, in-stream, low-flow structures across all or part of a stream channel. These measures have gained wide acceptance with national and state regulatory agencies responsible for protecting natural habitats because the structures often enhance stream habitat. Structure types include cross vanes, j-hooks, w-weirs, constructed riffles, and stream barbs usually constructed of rock riprap. Proponents of these structures have claimed that they can be durable and cost-effective and provide scour stability, but the necessary case studies have not been documented to verify these claims. Comprehensive engineering and financial criteria do not exist for evaluating, designing, installing, and maintaining these structures. In-stream, low-flow structures sometimes require less rock than traditional engineered streambank stabilization, promising greater economy, especially where material sources are scarce. The state of the art in design and installation does not include proven engineering design criteria, thus current efforts to apply these structures often result in frequent instances of failure and associated costs for repair. Validated engineering criteria promise reduced risk of failure and increased cost-effectiveness of installations. Quantitative optimization of parameters such as lifecycle cost, size, spacing, and foundation depth and their influence on scour depth, sediment transport, and long-term structure and channel stability will support the development of engineering design, installation, and maintenance criteria necessary for hydraulic engineers to design economic in-stream, low-flow structures with confidence.