Barrage or What

1
Barrage or What?

• Engineering Options

Prof Colin Taylor CEng FICE Professor of
Earthquake Engineering Head, Department of Civil
Engineering colin.taylor_at_bristol.ac.uk
2
The technical options

• Barrage
• Lagoon
• Tidal reef
• Tidal fence
• Tidal stream

Source Marc Paish, Severn Tidal Fence Group
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Barrage
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Barrage turbine
Source Roger Falconer
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Tidal lagoon
Source University of Colorado
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Fleming lagoon flow computation
Source Roger Falconer
Filling
Discharging
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Evans tidal reef
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Evans tidal reef
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Low-head turbine for reef
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Tidal fence
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Tidal stream
Source Swanturbines
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Short listed options
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Severn Tidal Fence Group
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Barrage issues

• Significant environmental impacts
• Reduction of water levels and tidal range
• Loss of inter-tidal habitats
• Impacts on bird and fish populations in the
  Severn
• Inhibits port traffic
• Protection from effects of storm surges, sea
  level rise
• Reduced turbidity
• Established technology

La Rance, France
15
Lagoon issues

• Significant reduction in tidal range within the
  impounded area
• Loss of inter-tidal habitats
• Other environmental effects are similar to
  smaller barrages
• Less impacts on fish and navigation as not a full
  a barrier across the estuary
• Enclosure construction uncertain (e.g.
  embankment, caissons, innovative modular
  concrete/earth units?)
• Longer than barrage

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Reef issues

• Unproven technology
• Long development period
• Less loss of tidal range
• Lower efficiency?
• Inhibits shipping

Source Evans Engineering
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Fence issues

• Unproven technology
• Long development period
• Less loss of tidal range
• Lower efficiency?
• Less impact on shipping (but vulnerable to ship
  impact?)

Source Marc Paish, Severn Tidal Fence Group
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Cost comparisons
Source DECC Analysis of Options report