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.

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.

Coastal protection for Ada, Ghana: a case study

Abstract: Along the northwest African coast average rates of coastal retreat are between 1 and 2 m per year. In Ada, Ghana, the shoreline retreat rates have been in excess of 6 m per year at some specific locations. As a result of the ongoing erosion, various properties and existing infrastructure are being damaged and destroyed; also, due to the poor condition of the beaches, and the presence of low-lying areas, Ada and other surrounding villages are prone to flooding. Hence, in 2010, the Ghanaian government decided to protect the coast in Ada along a distance of about 16 km. This paper discusses the aims and objectives of the coastal protection project in Ada, which consists of beach nourishment and groyne structures for its structural stabilisation. It also presents the main challenges of the project and the methods used to overcome these, as well as the successes and the lessons learned.

Bringing-up apparatus for providing repose place for yolk sac fry in fry channel

Abstract: A bringing-up apparatus is disposed in a channel having a fresh water inlet and outlet and provides in the channel areas of repose for yolk sac fry released to the channel. The bringing-up apparatus includes a plurality of groyne plates disposed in the channel such that they extend in a direction crossing the water flow in the channel and are spaced apart in the direction of the water flow for providing places of gentle water flow in the channel and also includes at least one support disposed on the bottom of the channel for supporting the groyne plates such that a space is maintained between adjacent groyne plates.

Coastal erosion along the sand barrier: Case study in Hue, Vietnam

Abstract: The problem in coastal erosion is wide spread in areas located in the coastal environment. However, in many developing countries, planning and coastal management have not gained much process due to several factors, one of which is the lack of understanding the influences in the coastal system. Vietnam is no exception to this problem. Located on the southeast of Asia, Vietnam has a coastline of approximately 2500 kilometers exposed to the South China Sea and Pacific Ocean. The marine environment, including the coastal area, plays an important role in the economic growth of the country. The importance of the coastal area is indicated by the fact that 75 percent of cities in the world with a population of 100,000 or more are located within this area. However, there are many conflicts of interest in coastal area that increasing number of problems needs to be solved. The most encountered problem is erosion, which occurs along the sandy barrier islands coast of Thua Thien Hue Province. The study area is located at Thuan An beach, 13 km from Hue city in northeast direction, situated at the middle of 120 kilometer coastline of the Province. Before come up to a solution for erosion problems along the coasts of Thua Thien Hue province, it is essential to understand the overall morphological behaviour of coastline evolution in region. Thus, the main objective of this study is to investigate the erosion mechanism, simulate the shoreline evolution; predict coastline development and propose measures for stabilizing the eroding beach in future. The results of the study show a net longshore transport pattern and longshore transport rate at each study location, which are influenced by the predominant wave direction from southeast and northwest. The changes in the coastline are results of gradients in net longshore transport distribution in each location. These changes are predominantly influenced by the characteristics of coastline and the migration of Thuan An inlet. In addition, human interventions with the construction of groyne field at south of Hoa Duan have influences these change. To prevent the continuing erosion on the beaches in study area, a groyne field was proposed. Some recommendations on groyne length, groyne space and their influence on the safety of structure itself and on the neighbouring coasts in future were made. In accompany with the "hard" solution, the study also propose a "soft" solution to immediately create an extended beach at Hoa Duan without cause any negative affects on the adjacent beach. There is much more to be done in order to get a sound understanding in the morphological behaviour of Thuan An inlet and the entire coastline system. lt is recommend setup a 2-D morphological mathematical modelling to investigate the morphology behaviour of Thuan An inlet. The possible morphological consequence in future of the inlet itself and neighbouring coasts also needs to study sufficiently. This is essential in creating the needed awareness for the adoption of a good coastal management programme for Thua Thien Hue Province.

3D flow simulation of straight groynes using hybrid DE-based artificial intelligence methods

Abstract: In this study, hybrid differential evolution algorithms were run to study the three-dimensional mean flow field around straight groynes. The three-dimensional velocity components in a refined mesh around a groyne were measured using an acoustic Doppler velocimeter. Two novel hybrid methods, namely differential evolution-based multilayer perceptron (DE-MLP) and differential evolution-based radial basis function (DE-RBF), were used to simulate the most significant flow features. It was found that the DE-MLP method modeled well the separation of the bottom boundary layer, downward deflection of the upper layers’ streamlines and horseshoe vortex (HSV) development at the upstream groyne face. However, the DE-RBF model was unable to predict the main flow features correctly, especially the HSV system. Both DE-MLP and DE-RBF models predicted the overall flow structure of the separation zone downstream of the groyne well. However, the RBF model could not predict the inflection points in the transverse velocity profiles, which are indicative of a mixing layer bounding the separation zone. The DE-RBF model underestimated the velocity amplification at the groyne head. The DE-MLP model perfectly simulated the distribution of the streamwise cross-stream Reynolds shear stress around the groyne head and also along the turbulent mixing layer.