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High Flow Sediment Bypass for Robles Diversion DamBrent Mefford, Blair Greimann, and Yong LaiTechnical Service CenterDenver, ColoradoMay 2008
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Aerial Views
Aerial view of Robles Diversion Dam, 2005 Aerial view with AutoCAD model overlay
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• Crest Elevation: 767 ft• Structural Height: 24 ft• Hydraulic Height: 13 ft• Crest Length: 530 ft• Volume: 11,000 yd3
Background
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• Sluice Radial Gate Structure– 4 Radial gates (1-10’x9.5’, 3-16’x9.5’)
• Discharge Capacity: 6,000 cfs– Associated features:
» Spillway & Baffle Section
Existing Conditions
• Diversion Canal– 3 Radial gates (11’ x 10.5’)
• Discharge Capacity: 500 cfs
Downstream of Sluice Radial Gate Structure
Sluice Radial Gate Structure (Left)and Diversion Canal (Right)
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Existing Conditions• Downstream
– Boulders & Cobbles– Vegetation
Downstream of Sluice Radial Gate Structure (Left)
Upstream
Downstream
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Existing Conditions
Sedimentation at Fish Entrance
2005 Flood (less than 10-yr flood)
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Existing Conditions
Entrance Conditions at Gates
2005 Flood (less than 10-yr flood)
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overtopping and damage to dam
2005 Flood (less than 10-yr flood)
Existing Conditions
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Existing Conditions
Debris Loads at Fish Screens
2005 Flood (less than 10-yr flood)
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• Determine flow capacity and the best location for the spillway structure (left bank or right bank) based on sediment sluicing performance and impacts on upstream fish passage.
• Identify potential modifications to the design that would enhance sediment sluicing, fish passage and minimize the potential for fish stranding.
• Identify spillway operational patterns that promote sediment sluicing fish passage and prevention of fish stranding.
Objectives
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• Physical Model: – Tested with and without HFSB– Tested Medium flow (6,000 cfs) and higher flow (14,000
cfs)• Numerical Modeling:
– compared against laboratory experiements– Simulated without and without Matilija Dam Removal– Simulated without and without HFSB
• Fish Passage:– Designed and tested single pool with fish ladder
Tasks
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• Bed load at Robles Diversion will increase after Matilija Dam Removal, potentially entering canal and reducing diversions
• HFSB improves the sediment sluicing and will reduce the bedload entering Robles Canal
• Existing debris loads and suspended sediment loads will remain high
• Existing fishway entrance will need to be raised due to sedimentation
• Additional fish ladder will minimize fish stranding at HFSB
• Raise of dam crest provides greater operational flexibility for diversion and fish ladder
Summary of Results
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Final Design Recommendations
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Design Recommendations
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Downstream of Diversion
Existing spillway
HFSB
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Downstream of Diversion
Fishwayexit
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Downstream of Diversion
HFSB Spillway
Fishwayentrance
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• Test Conditions– Existing Conditions
• Assuming Matilija Dam Removed– Sluice Radial Gate Structure– Diversion Canal Structure
– Proposed Conditions• High Flow Sediment Bypass (HFSB)
Radial Gate Structure
– 4 Radial gates (10’ x 30’)– Discharge Capacity: 11,000 cfs
• Sluice Radial Gate Structure• Diversion Canal Structure
Physical Model
Sluice Radial Gate Structure (Left)and Diversion Canal (Right)
High Flow Bypass Radial Gate Structure
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Physical Model
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Physical Model
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• Test Flows– 6,000 cfs
• 1991 Flood
– 14,000 cfs • 1998 Flood
Physical Model Tests
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• Water Surface Elevations– Point Gages
• Dam Crest• Upstream Fishway Exit• Upstream of Spillway Weir
• Velocity– Recorded during peak flow– Measured 1’ (20’ prototype) from upstream toe of dam
• 8 stations– 2.5’ centers
– Deposition• Photogrammetry
– Estimate sediment volume– Survey
• Sediment elev. along downstream perimeter of depositions– Soil samples
• Gradation analysis to compare with original sediment bed composition
Data Collection
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Current Condition Test Results
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• Existing Conditions – Sluice Radial Gate Structure & Diversion Canal
• Sediment passes through both structures• Sediment deposits in spillway and diversion canal
Results – 6,000 cfs
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• Existing Conditions – Sluice Radial Gate Structure & Diversion Canal
Results – 6,000 cfs
Upstream of Sluice Radial Gate Structure
Spillway Downstream of Sluice Radial Gate Structure
Upstream of Diversion Canal
Upstream Fishway Exit
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• Sediment Quantities– 3.14 yd3 placed in model– 0.049 yd3 accumulated upstream of spillway weir 1– 0.011 yd3 accumulated within diversion canal
Results – 6,000 cfs• Existing Conditions
– Sluice Radial Gate Structure & Diversion Canal
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• Existing Conditions – Sluice Radial Gate Structure & Diversion Canal
• Sediment passing through both structures• Sediment fills spillway & diversion canal• Sediment reaches crest of dam
Results – 14,000 cfs
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• Existing Conditions – Sluice Radial Gate Structure & Diversion Canal
Results – 14,000 cfs
Upstream of Sluice Radial Gate Structure & Dam Crest
Spillway Downstream of Sluice Radial Gate Structure
Downstream of Diversion Canal
Upstream Fishway Exit
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• Sediment Quantities– 5.63 yd3 placed in model– 0.281 yd3 accumulated upstream of spillway weir 1– 0.131 yd3 accumulated within diversion canal
Results – 14,000 cfs• Existing Conditions
– Sluice Radial Gate Structure & Diversion Canal
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Proposed Condition Test Results
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• Proposed Conditions – Sluice Radial Gate Structure & Diversion Canal – High Flow Bypass Radial Gate Structure (At Right Bank)
• Sediment passing through both structures• Sediment fills spillway, Diversion Canal clear
Results – 6,000 cfs
High Flow Bypass Structure Sluice Radial Gate Structure
Diversion Canal
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Results – 6,000 cfs
Upstream of Sluice Radial Gate Structure& Diversion Canal
Baffle Section Downstream of Sluice Radial Gate Structure
Upstream Fishway Exit
• Proposed Conditions – Sluice Radial Gate Structure & Diversion Canal – High Flow Bypass Radial Gate Structure (At Right Bank)
Upstream of HFSB Radial Gate Structure
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• Proposed Conditions – Test Velocities
Results – 6,000 cfs
Image at 2.40 cfs (4,293 cfs)
15-18 ft3/s
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• Sediment Quantities– 4.58 yd3 placed in model– 0.000 yd3 accumulated upstream of spillway weir 1– 0.000 yd3 accumulated within diversion canal
Results – 6,000 cfs• Proposed Conditions (Right Bank)
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• Proposed Conditions – Sluice Radial Gate Structure & Diversion Canal – High Flow Bypass Radial Gate Structure (At Right Bank)
• Sediment passing through both structures• Sediment fills spillway, Diversion Canal clear
Results – 14,000 cfs
High Flow Bypass Structure
Sluice Radial Gate Structure
Diversion Canal
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Results – 14,000 cfs
Upstream of Sluice Radial Gate Structure& Diversion Canal
Spillway Downstream of Sluice Radial Gate Structure
Upstream Fishway Exit
• Proposed Conditions – Sluice Radial Gate Structure & Diversion Canal – High Flow Bypass Radial Gate Structure (At Right Bank)
Upstream of HFSB Radial Gate Structure
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• Proposed Conditions (Right Bank)– Test Velocities
Results – 14,000 cfs
Image at 7.90 cfs (14,132 cfs)
15-18 ft3/s
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• Sediment Quantities– 5.85 yd3 placed in model– 0.383 yd3 accumulated upstream of spillway weir 1– 0.000 yd3 accumulated within diversion canal
Results – 14,000 cfs• Proposed Conditions (Right Bank)
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• Sluice Gate Radial Structure Spillway – Filled during high flows
• Diversion Canal Structure– Clear during high flows with
HFSB Structure in place
• Fish Bypass Structure– Plugged during high flows
at both entrance and exit
• Gate Operations– Aids in directing sediment
transport
Physical Model Study Conclusions
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Numerical Model Results: Without HFSB
(b) After Matilija Dam removal(a) before Matilija Dam removal
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Numerical Model Results: after Matilija Dam Removal
(b) With HFSB(a) Without HFSB