|Shields Jr, Fletcher|
Submitted to: ASAE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: 12/1/1998
Publication Date: N/A
Interpretive Summary: Woody vegetation and large woody debris are key components of stream corridors in agricultural watersheds, but historically they have been underemphasized by the traditional engineering and physical sciences. The role that vegetation and debris play in stream ecosystems has been better defined, and reforestation of stream corridors and riparian buffers is increasingly recommended. More recent field and laboratory research has investigated effects of woody vegetation on the ability of channels to convey water, on patterns of erosion and sediment deposition, and on the durability and reliability of riparian structures like flood control levees and streambank protection revetments. Relevant literature dealing with recent advances in this area is reviewed and summarized. The review will provide a foundation for future research and demonstration in uses of vegetation and woody debris to rehabilitates stream corridors damaged by erosion and sedimentation.
Technical Abstract: Rehabilitation of river corridors often involves restoring riparian and floodplain plant communities, among other measures. Adoption of policies requiring riparian zones or forested buffers along streams is gaining popularity. From an engineering standpoint, much is unknown about the effects of vegetated boundaries on streams. Recent advances in understanding vegetative effects on flow, sediment transport, and stream stability are reviewed. Different approaches are used for computing flow resistance due to flexible and rigid vegetation. In general, resistance due to flexible vegetation declines with increasing flow, while rigid vegetation (and woody debris) resistance is related to flow in a more complex fashion. The impact of vegetation on the flow field leads to enhanced deposition within and adjacent to vegetated zones, and possibly erosion elsewhere. Woody vegetation influences the shape of the channel cross-section partially because of the effects of plant roots on bank stability. Woody debris can exert a major influence on channel hydraulics and morphology, and thus should be viewed as a primary tool for restoration. Site factors must be carefully evaluated when designing vegetative treatments.