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Introduction to Stream Deflectors

Introduction to Stream Deflectors. 14.

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Introduction to Stream Deflectors

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  1. Introduction to Stream Deflectors 14 This training was prepared by the U.S. Department of Agriculture (USDA) team of Otto Gonzalez-USDA Foreign Agricultural Service (Team Leader), Jon Fripp (Civil Engineer) and Chris Hoag (Wetland Plant Ecologist)-USDA Natural Resources Conservation Service (Civil Engineers). Fripp and Hoag were the primary authors of this material. The U.S. AID provided funding support for the USDA team.

  2. Stream Deflector Protection • Usually Used in Transport Zone • Diverts Stream Energy Away from the Stream Bank

  3. What is a stream deflector? Answer: A stream deflector is a structure that extends into the stream from the bank to redirect streamflow away from an eroding bank. Stream Deflectors: • Are low structures that are oriented upstream, into the flow. • Slow water velocities • Induce sediment deposition Harland Creek MS

  4. They can be big

  5. Stone Spurs Hard Points and/or Kickers They can be smaller

  6. Stream Deflectors Design Criteria • Understand basic principles of how stream deflectors work • Stone Size • Alignment • Design • Profile • Key into bed • Key into bank There are a lot of different types. Design often requires an engineer This introduction is going to cover the basics You may want to get more detailed training

  7. How Do Stream Deflectors WorkThese structures slow stream velocity near bank Question: Why is this useful when you want to stop bank erosion? Answer: Slower velocity = less erosion Sediment that is naturally in the stream will drop out of the flow when the water slows Typically the protection is 3-4 times the length of the deflector Bank Line

  8. Stone size • The force of the river or stream hits the deflector directly • Therefore the stone must be larger than riprap on bank • Suggest that the minimum size is twice the calculated riprap size

  9. Works with • Alignment • Can Vary • Use 45 degrees from bank • Clap a 90 degree angle than half Flow Approximately 45° Pointed up stream Angle varies depending on radius of bend Do not use on too tight of a bend

  10. Deflectors are often used in groups The angle may vary Redirected flow Captured flow Flow is controlled within the set of deflectors keeps the same basic curve

  11. Design: Profile Length < 1/3 channel width Maximum Bank Height = smaller of 1 meter or 1/3 total bank height End Height = ½ Bank Height End Height Bank Height Length

  12. Design: Bed Key Bed key = 1 to 2x height Bed key

  13. Design: Bank Key Bank key is larger of 1 meter or bank height Bankkey

  14. You need an engineer to help with the design if: • The river has high velocities • The river is large • The erosion is significant • The river system is unstable • There is something very important on the bank • The project will cost a lot of money • Laws state you must have an engineer

  15. The End

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