Tidal Range Barrage Design and Construction

The west coast of Great Britain has the potential for barrages to create tidal range reservoirs that both facilitate electricity generation and prevent flooding from sea level rise. Seawater flows into and out of the reservoir, or impoundment, through turbines and sluices. The impounded water follows the natural tidal sequence but with a delay which creates a head between the two bodies of water. Traditional designs for barrages use earth embankments, with impermeable cores and rockfill protection. More recently, breakwaters and jetties have been constructed using precast concrete vertical caissons. A novel design using horizontal precast caissons is described and evaluated. Wave forces are estimated using Goda’s method for a vertical breakwater to assess their impact on stability and ground-bearing pressures. The stability of the barrage is checked for hydrostatic and wave forces. The volumes of materials and relative costs are presented. Precast caissons are found to be viable financially and should be both quicker and easier to construct and install. The horizontal caissons show advantages over the vertical type, and although untried, they should be easier to construct than submerged tube tunnels. Further work is needed to validate the design, including dynamic modelling and detailed construction assessment to confirm the cost rates.