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Brent Mefford, P.E. – Wild Fish Engineering Bryan Heiner, P.E. – U.S. Bureau of Reclamation August 2014Clark Fork Coalition - Small-Scale Fish Screen Workshop.

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Presentation on theme: "Brent Mefford, P.E. – Wild Fish Engineering Bryan Heiner, P.E. – U.S. Bureau of Reclamation August 2014Clark Fork Coalition - Small-Scale Fish Screen Workshop."— Presentation transcript:

1 Brent Mefford, P.E. – Wild Fish Engineering Bryan Heiner, P.E. – U.S. Bureau of Reclamation August 2014Clark Fork Coalition - Small-Scale Fish Screen Workshop

2 Why Screen? Fish screening can serve multiple objectives: Fish Protection Debris Management Sediment Management August 2014Clark Fork Coalition - Small-Scale Fish Screen Workshop

3 Fish Protection Preventing fish from being entrained or injured by diversion of flow from a stream, lake or canal. Positive Barrier: exclude all aquatic organisms larger than the screen hole size. Behavior Barrier: guide fish away from diversions using louvers, bar rack, sound, light, electricity, air bubbles curtains or a combination of these. - Does not exclude all fish. August 2014Clark Fork Coalition - Small-Scale Fish Screen Workshop

4 Debris Management To operate properly, a screen MUST BE designed to manage the inflow of debris. Exclude Debris from the diversion, leaving it in the stream/lake. Pass Debris entrained by the diversion downstream with the screened water. Remove Debris from the diverted water and collect it onsite. August 2014Clark Fork Coalition - Small-Scale Fish Screen Workshop

5 Sediment Management Screens can be designed to aid in the management of sediment moving with the diverted water. Larger bed sediments (bedload): roll along the channel bottom. Typically sand & gravel. Finer suspended sediment: fine sand, silt and clay that are suspended and carried within the water as a mixture. August 2014Clark Fork Coalition - Small-Scale Fish Screen Workshop

6 Screen Basics – V a & V b Approach Velocity (V a ) – flow velocity measured perpendicular to the screen surface. Should be less than the fish’s sustained swimming ability. Sweeping Velocity (V s ) – flow velocity measured parallel to the screen surface. Should be larger than V a to allow fish and debris the be swept away from the diversion flow. August 2014Clark Fork Coalition - Small-Scale Fish Screen Workshop SCREEN VaVa VsVs VcVc

7 Screen Basics – Velocity Ratio August 2014Clark Fork Coalition - Small-Scale Fish Screen Workshop Velocity Ratio

8 Screen Basics - Baffles Baffles are often required to ensure that even approach velocities across the entire screen area are achieved. August 2014Clark Fork Coalition - Small-Scale Fish Screen Workshop Screen Baffles

9 Screen Basics – Approach Flow Approach Channel Flow It is important to have a uniform flow entering the screen area to prevent unwanted impingement zones August 2014Clark Fork Coalition - Small-Scale Fish Screen Workshop

10 Screen Basics - Location In-Ditch In-Stream/Lake August 2014Clark Fork Coalition - Small-Scale Fish Screen Workshop

11 Screen Basics – In-Ditch In-Ditch Pros: Ease of dewatering the screen for inspection & maintenance Flow conditions are typically more predictable & controlled In-Ditch Cons: Requires fish bypass Requires more water at the stream/lake diversion Bypassed fish are more susceptible to predators August 2014Clark Fork Coalition - Small-Scale Fish Screen Workshop

12 Screen Basics – In-Stream In-Stream/Lake Pros: No fish enter diversion No fish bypass required In-Stream/Lake Cons: Maintenance access may be difficult or limited Screen may need to be removed during freezing weather Large debris may damage screen Flow conditions may be highly variable August 2014Clark Fork Coalition - Small-Scale Fish Screen Workshop

13 Screen Basics – Material Fish screens are designed with a metal frame and a screen fabric. Screen Porosity: % open area of the screen. Headloss: drop in water surface or pressure across the screen. Hole Size: important to consider to meet criteria based on life stage & debris loading (several X smaller or larger than dominant debris). August 2014Clark Fork Coalition - Small-Scale Fish Screen Workshop

14 Screen Basics – Woven Wire Woven Wire Screen: Low cost Requires closely spaced supports Can be difficult to clean Square or rectangular openings Creates a rough surface Best where debris loads are light August 2014Clark Fork Coalition - Small-Scale Fish Screen Workshop

15 Screen Basics – Perforated Plate Perforated Plate Screen: Low cost Can requires closely spaced supports Smooth surface Round openings August 2014Clark Fork Coalition - Small-Scale Fish Screen Workshop

16 Screen Basics – Wedge-Wire Wedge-Wire Screen: Smooth upstream face Expanding orifice opening in profile Requires minimal support structure Durable Expensive August 2014Clark Fork Coalition - Small-Scale Fish Screen Workshop

17 Screen Basics – Tilted Wedge-Wire Wedge-Wire Screen: Smooth upstream face Expanding orifice opening in profile Requires minimal support structure Durable Expensive Can pass more flow August 2014Clark Fork Coalition - Small-Scale Fish Screen Workshop

18 Screen Basics – Other Types Many modeled or woven fabrics are available in synthetic materials August 2014Clark Fork Coalition - Small-Scale Fish Screen Workshop

19 Screen Basics – Cleaning All fish screens require periodic maintenance but will reduce downstream maintenance if designed appropriately. Cleaning methods available: Back-flush Mechanical Natural August 2014Clark Fork Coalition - Small-Scale Fish Screen Workshop

20 Screen Basics – Back-flush August 2014Clark Fork Coalition - Small-Scale Fish Screen Workshop

21 Screen Basics – Back-flush August 2014Clark Fork Coalition - Small-Scale Fish Screen Workshop

22 Screen Basics - Mechanical August 2014Clark Fork Coalition - Small-Scale Fish Screen Workshop

23 Screen Basics - Mechanical August 2014Clark Fork Coalition - Small-Scale Fish Screen Workshop

24 Screen Basics - Natural August 2014Clark Fork Coalition - Small-Scale Fish Screen Workshop

25 Screen Basics - Conclusion The basics of screening offer many different options for designing screens. Many times even after considering all the options screens are still a trial and error process and some modifications/changes may be required after a screen is installed. Questions? August 2014Clark Fork Coalition - Small-Scale Fish Screen Workshop


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