Flow Structures
The basic premise behind in-channel stream management structures is that when water encounters a barrier to flow, it will cross that obstacle in a direction perpendicular to the orientation of the structure. The effectiveness of these structures lies in their ability to direct flow through and over their rock walls. Water is directed away from the bank to prevent erosion. Simultaneously, this concentration of flow carves a deeper channel in the middle of the stream. Flow "waterfalling" over the rock surface serves to deepen and elongate the scour pool. Dave Rosgen, the pioneer in this field, investigates the dynamics of stream flow in his paper on stream stabilization and river restoration, which you can view at this site. Here, the three stream management structures implimented in Seven Mile Creek are illustrated and explained.*
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Cross Vanes
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J-Hook Vane
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Willows
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*Diagrams from Rosgen, D.L. The Cross-Vane, W-Weir, and J-Hook Vane, Structures...Their Description, Design and Application for Stream Stabilization and River Restoration. http://www.wildlandhydrology.com/assets/cross-vane.pdf