Environmental Considerations for Vegetation in Flood Control Channels.

摘要

This report describes the environmental benefits of riparian vegetation and presents considerations for the incorporation of riparian vegetation into the design and maintenance of flood control projects. The report is directed toward hydraulic engineers involved in flood control channel design as well as stream restoration and habitat improvement projects. The ability to predict or account for impacts associated with vegetation on streams and flood control projects is hampered by a lack of understanding of the physical processes that occur when water flows through and over vegetation. Vegetation can cause conveyance loss, induce sediment problems, increase flooding, and disrupt normal channel-floodplain interactions. The tools typically used for evaluating open channel flow do not typically allow for consideration of the varied effects of vegetation. Therefore, hydraulic engineers have long been reluctant to incorporate many types of vegetation into designs because of the hydraulic and sediment uncertainties. But healthy riparian vegetation also stabilizes streambanks, provides shade that prevents excessive water temperature fluctuations, performs a vital role in nutrient cycling and water quality, improves aesthetic and recreational benefits of a site, and is immensely productive as wildlife habitat. For these reasons, the incorporation of vegetation in stream restoration and flood control projects is often desirable.