Effectiveness of control structures on shingle beaches - physical model studies

Coates, T. (1994) Effectiveness of control structures on shingle beaches - physical model studies. Technical Report. HR Wallingford, Wallingford.

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Abstract

Shingle beach response in the presence of groynes and detached breakwaters was investigated using a 1:50 mobile bed physical model. The study is part of an ongoing coastal research programme at HR Wallingford. The groynes study investigated a number of structural variables for both timber and rock groynes under a range of sea conditions. Groyne effectiveness is determined from measurements of longshore transport, cross-shore distribution of transport, beach profiles, plan shapes and volumes. The conclusions drawn are not directly applicable to site situations, but indicate a number of factors that should be considered during groyne design for recharged beaches. Field verification of the model results, followed by further modelling are necessary before general design guidelines can be specified. The breakwater study concentrated on single rubble mound structures, but concluded with a brief series of tests on pairs of structures. Structural variables include length, freeboard, distance offshore and gap width. The study is more conclusive than the groynes work, though it is also limited by the variables tested and the lack of field verification. A design approach is proposed which relates the dominant structural variables to potential and actual sediment drift rates. Further work will allow the proposed approach to be developed in to a general design method. A final chapter is included which attempts to place the research results in to a practical engineering context. Users of this report must be aware of the limitations of the available experimental and field data.

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