Showing papers on "Groyne published in 1994"

Effectiveness of control structures on shingle beaches - physical model studies

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.

Stability of rock armoured beach control structures

Abstract: Control of shingle beaches for coast protection and/or sea defence may require use of rock groynes or shore-detached breakwaters. Experience from coast protection schemes on shingle beaches along the south coast of England however suggests that some control structures, including rock groynes and rubble revetments, have suffered greater damage than had been expected. This damage seems to have been most closely associated with steeper beach slopes. This report summarises information from recent research studies on the stability/damage behaviour of rock armour on 4 general beach control structures: a) simple 1:2 rubble sea wall slope; b) rock bastion or roundhead groyne; c) inclined crest rock groyne; d) L-shaped rubble groyne adapted from b) above. The report is aimed at coastal engineers who require information on the analysis/design of rock armoured beach control structures. It summarises data from a number of previous studies by HR Wallingford and co-workers, and includes results from recent wave basin tests.

3D model verification for a groyne and harbor experiment

Abstract: A discussion of 3D model verification and calibration based on measurements in a flume is carried out for different test cases (groyne, harbor). The measurement data is available for public access. The numerical 3D model is based on the Finite Element Method using a multilayer approach in the vertical direction. The goal is to show how different terms in the model equations may be tested in their interaction and to which limit the parameterizations are valid.