Groynes

Groynes in coastal engineering (CIRIA C793), published by CIRIA in 2020, defines a groyne as a: ‘Narrow, roughly shore-perpendicular structure built to reduce or divert longshore currents and/or to trap and retain beach material. Most groynes are of timber or rock, and extend from a seawall, or the backshore, well onto the foreshore and rarely even further offshore.

It defines groyne efficiency as: ‘The fraction of the unconstrained instantaneous longshore sediment transport past a groyne which is retained by the groyne. This efficiency may reduce with time as the groyne deteriorates or as the groyne bay fills.’

Where a groyne bay is the compartment between two groynes.

And a terminal groyne as the: 'Last groyne at the downdrift end of a groyne field. This groyne will need to be a substantial structure to remain stable given the (potentially significant) erosion downdrift.'

[edit] Related articles on Designing Buildings Wiki

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• Breakwater.
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• Coastal change management area.
• Coastal defences.
• Difference between cofferdams and caissons.
• Dredging.
• Flood defences.
• Land-sea interface.
• Planning for floods.
• Temporary flood defences.