Groyne

About: Groyne is a research topic. Over the lifetime, 397 publications have been published within this topic receiving 4549 citations. The topic is also known as: groin & Breakwater.

Coastal engineering problems at Clacton-on-Sea, Essex

Abstract: Summary Erosion along the frontage at Clacton has necessitated the progressive protection of the cliff and foreshore during the last 100 years. The cliffs consist of Pleistocene gravels overlying London Clay and reach a level of 20 m above Ordnance Datum (Newlyn). The top of the clay is irregular and incised by buried channels which allow water to drain to the front of the cliff and weaken the clay forming the cliff base. On the foreshore the stability of the existing sea walls protecting the cliff base was endangered by erosion on the downdrift side of the two large groynes constructed a few years previously. Remedial measures included the relief of perched water tables and drainage of the cliff by vertical and inclined bored drains; the protection of the toe by constructing stepped aprons and sea walls of pre-cast concrete components; the installation of a new groyne system and replenishment of foreshore material.

Morphological Trends of the Belgian Coast Shown by 10 Years of Remote-Sensing Based Surveying

Abstract: The morphological evolution of foreshore, backshore, and adjoining dunes of the entire Belgian coast is surveyed by means of aerial remote sensing on a yearly basis since 1983. The evolution over this 10-year period is comprehensively illustrated by the land-and seaward shifts of the low-water line, high-water line and dune foot. It appears that nearly all major displacements are linked to human interactions, such as beach nourishments, groyne construction, etc. If these are left out of consideration, the main trend of the coastline evolution would be a landward retreat. Since 1986, the results of the bathymetric BEASAC measurements of the nearshore area linked to the aerial remote sensing surveys.

An assessment of processes and strategies for management of the Penarth Coast

Abstract: In 1997, the effects of severe erosion along the Penarth foreshore became apparent when the beach surface fell to critical levels. From consideration of global influences, the physical and cultural environments and anthropogenic activities, including the construction of the Cardiff Bay Barrage, a five-year monitoring programme was devised to assess coastal processes, identify possible causes of the erosion and develop management strategies for protection of the Penarth coast. Approximately 1·5 km of the foreshore, comprising two orientations, NNE and NNW, were surveyed each September and April between 1997 and 2002, to assess summer and winter changes. Results showed in September 1997, sediment transport was southerly in direction whilst from April 2000, there was a consistent return to the traditionally accepted south to north longshore drift; verified by significant differences in longshore gradients. Foreshore analysis provided important regression models representing the variation of the shoreline indicator Mean High Water (MHW) with shoreline position (mean beach level) and gain/loss of beach material. Models represented the temporal variation of MHW and depth of closure with further significant correlation between the two-shoreline indicators (83·85%). A Management Response Indicator (MRI) equation provided a simple tool to rapidly assess the health of Penarth beach, MRI = 17·035 +tan·' (x14- x6)/240, whilst temporal variation of longshore gradients, demonstrated an important inter-relationship between beach evolution and orientation (97·37%). Significant temporal and spatial models identified changes in beach formation adjacent to the Barrage breakwater pre and post construction and showed its influence decreased with distance. A further management tool was developed to monitor beach evolution and morphological change in response to this structure. Analysis of ten-year water and wind data identified a projected mean sea level rise of 0-4mm/year and significant increases in easterly wind components between 1995 and 1997, coinciding with significantly higher extreme water levels. Following correlation of these forcing agents with shoreline indicators, supported by documented beach losses of 350 kg/m2 subsequent to an easterly storm, it was concluded that the unprecedented erosion of Penarth beach was caused by increased wave attack from the northeast and southeast quadrants. Function Analysis justified foreshore management from a development perspective whilst risk analysis supported management strategies. Initial recommendations of on-going monitoring to assess beach health were supported by developed models and underpinned by management responses detailed for each of three defined beach sections. These included beach nourishment, wave wall construction in conjunction with the proposed Penarth Headland Link and groyne removal adjacent to the Barrage.

An evaluation of design factors and performance of groynes

Abstract: Groynes have been widely used for generations for preventing coastal erosion throughout the world. As coastal processes in a groyne system are complex and the groyne design is largely based on crude empirical methods, it is not always possible to ensure groyne performance at the design stage. Postproject appraisal is therefore of vital importance in assessing the actual performance and adequacy of the design methodology. This article presents the findings from an extensive questionnaire survey that has recently been carried out to assess the performance of existing groynes at many sites in the UK. Factors such as groyne configurations, the types of beach materials, and types of groynes on the performance of these groyne systems have been evaluated in detail. It has been found that the majority of groynes analysed are effective in preventing erosion of the groyned shoreline and that rock groynes perform particularly well compared with the traditional timber groynes.

Three-dimensional Flow In A Barb Field

Abstract: Barbs (or submerged groynes) are low-profile linear rock structures that are primarily used to prevent the erosion of stream banks. They are a variation of a groyne, similar to spur dikes and bendway weirs. Barbs are typically anchored, in series, to the outside bank in stream bends and extend in an upstream direction from the bank into the flow. This configuration redirects flow away from the outer stream bank and disrupts the velocity gradient close to the outer bank, encouraging sediment deposition adjacent to the barb. These interactions between the flow pattern and the sediment transport around the barb prevent erosion of the bank. Furthermore, vortices generated by the barb create local scour holes that can enhance aquatic habitat. A three-dimensional numerical model, Sediment Simulation in Intakes with Multiblock option (SSIIM), was used to examine the turbulent flow field and associated scour and depositional patterns due to a series of barbs in a mobile-bed channel bend. Previous physical model observations were used for model calibration and verification. Barb design was optimized to minimize scour. The parameters considered in the optimization were channel bend angle, barb alignment angle, and barb spacing. In this paper the spatial distribution of the three-dimensional flow field through a series of barbs in a 90o channel bend are mapped and the impact on the flow field of subtle differences in barb geometry are examined. Special emphasis is placed on the influence of barb design on secondary currents in the meander bend and the generation of three-dimensional vortices, and the consequent impact on scour.