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> Programme design  > Defence Type > Groynes 

Groynes

Groynes are regularly used as part of sediment control systems. Timber groynes have historically been the choice of many organisations, as sediment control structures. Rock groynes have been introduced at a number of sites since the 1980s. Surprisingly little is known about the effectiveness of either of these types of structure, despite the widespread use of a range of structure styles. Numerous numerical models have been developed to predict the performance of groyne systems, but these are rarely calibrated or validated with adequate field data; the models are reliant upon energy-based principles and are unable to deal with all of the site-specific variables relating to sediment availability and size grading distributions. High quality monitoring data is required therefore to improve measurement of system performance and to evaluate performance of existing design tools.

Sandown Bay - Sand beach with groynes
Rock groyne system Hengistbury Head

Without regular maintenance of groyne systems they degrade and can become dysfunctional.

Undermined groyne system

Considerable investment has been made at many sites incorporating groynes and beach recharge. Performance of such schemes needs to be monitored regularly to determine performance effectiveness of the scheme. Beach data used in context with geometric configurations of groynes can be used to optimise the design geometry of groyne systems.

Recharged timber groyne system - Eastbourne

Groynes are usually introduced on stretches of shoreline where the longshore sediment transport rate is high; this often results in differential levels across the width of each groyne compartment. These changes are best described either by detailed surface models developed from spot height surveys, or by sample groups of 3 profiles within a single groyne compartment.

Differential levels at the up-drift and down drift ends of a groyne compartment
Updated 23rd January 2003 Geodata