scholarly journals APPLICABILITY OF SUB-SAND SYSTEM TO BEACH EROSION CONTROL

1986 ◽  
Vol 1 (20) ◽  
pp. 92 ◽  
Author(s):  
Yoshiaki Kawata ◽  
Yoshito Tsuchiya
Keyword(s):  
Normal Wave ◽  
Erosion Control ◽  
Beach Erosion ◽  
Beach Profile ◽  
Sand Filter ◽  
Beach Sediment ◽  
Filter System ◽  
Fluid Boundary ◽  
Wave Conditions ◽  
Control Work

We performed experiments in the laboratory under controlled conditions in order to determine the applicability of a sub-sand filter system to the beach erosion control work. The filter system is used to control a flow condition at the sediment-fluid boundary. In the foreshore, it increases the inflowing velocity into the beach and thus results in increasing the threshold of beach sediment movement. The sub-sand filter system accelerates accretion of much beach sediment in the foreshore through the development of a berm under normal wave conditions. When wave conditions change from normal to stormy , it is also applicable to stabilize the beach profile, and thus decrease loss of beach sediment from the foreshore to the offshore.

scholarly journals MOVABLE-BED MODEL STUDIES OF PERCHED BEACH CONCEPT

1972 ◽  
Vol 1 (13) ◽  
pp. 60
Author(s):  
C.B. Chatham
Keyword(s):  
Three Dimensional ◽  
Normal Wave ◽  
Beach Erosion ◽  
Model Studies ◽  
Model Study ◽  
Wide Range ◽  
Final Design ◽  
Storm Wave ◽  
Wave Conditions ◽  
Movable Bed

Hydraulic model studies were conducted to aid in ascertaining the technical feasibility and optimum design factors of the perched beach concept. Among these were two-dimensional, movable-bed studies to determine an estimate of the amount of sand which would be lost seaward over the submerged toe structure by normal and storm wave action, the optimum elevation of the submerged toe structure, and the length of a stone blanket required to reduce seaward migration of sand to a minimum. The model beach was subjected to test waves until equilibrium was reached for a wide range of wave conditions for both the existing beach and the perched beach. Test results indicate that (a) little or no beachfill material will be lost seaward of the toe structure for normal wave conditions but the larger storm waves may cause erosion of the perched beach, (b) the installation of a stone blanket shoreward of the toe structure will reduce the amount of beach erosion, (c) if the beach fill is extended a sufficient distance seaward, the toe structure serves no useful purpose, and (d) a three-dimensional movable-bed model study is feasible and is necessary to determine the final design features of a perched beach.

scholarly journals THE GEOLOGICAL ASPECTS OF COASTAL ENGINEERING

2010 ◽  
Vol 1 (1) ◽  
pp. 13
Author(s):  
John W. Handin
Keyword(s):  
Erosion Rate ◽  
Coastal Engineering ◽  
Beach Erosion ◽  
Supply Rate ◽  
Secular Equilibrium ◽  
Equilibrium Conditions ◽  
Beach Sediment ◽  
Stable Position ◽  
Shore Line ◽  
Sand Supply

A natural beach system is in equilibrium when there is a balance between sand supply and erosion such that the volumes of material entering and leaving the system are just equal. If the erosion rate exceeds the supply rate, a beach retrogrades; if the erosion rate is less than the supply rate, a beach progrades. Unfortunately, coastal engineering works, which are meant to improve the shore for commerce or recreation, often upset this delicate balance with very deleterious results: great accretions of sand and high dredging costs, accelerated beach erosion and much property damage. It is the task of the geologist to determine the secular equilibrium conditions of a beach system and to supply the coastal engineer with the information he needs to control the natural forces acting on the shore in such a way that this equilibrium is maintained. In order to accomplish this task, the geologist needs to make a thorough study of the source, transportation, and deposition of beach sediment. He must determine the stable position of the shore line and the profile of equilibrium of the beaches through detailed physiographic investigations. The geological report can and should close with the prediction of just what will happen to a natural beach system if man introduces a disturbing element.

scholarly journals Streptophyta and Acetic Acid Bacteria Succession Promoted by Brass in Slow Sand Filter System Schmutzdeckes

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Ma. Carmen E. Delgado-Gardea ◽  
Patricia Tamez-Guerra ◽  
Ricardo Gomez-Flores ◽  
Mariela Garfio-Aguirre ◽  
Beatriz A. Rocha-Gutiérrez ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Acetic Acid Bacteria ◽  
Sand Filter ◽  
Filter System ◽  
Slow Sand Filter

Current countermeasure of beach erosion control and its application in Taiwan

2010 ◽  
Vol 53 (9) ◽  
pp. 552-561 ◽  
Author(s):  
Ray-Yeng Yang ◽  
Ying-Chih Wu ◽  
Hwung-Hweng Hwung ◽  
Jiing-Yih Liou ◽  
Igor V. Shugan
Keyword(s):  
Erosion Control ◽  
Beach Erosion

A RANS numerical model for cross-shore beach profile evolution

2020 ◽  
Author(s):  
Julio Garcia-Maribona ◽  
Javier L. Lara ◽  
Maria Maza ◽  
Iñigo J. Losada
Keyword(s):  
Sediment Transport ◽  
Numerical Model ◽  
Transport Model ◽  
Numerical Models ◽  
Computational Cost ◽  
Physical Modelling ◽  
Computational Effort ◽  
Beach Profile ◽  
Time Step ◽  
Wave Conditions

<p>The evolution of the cross-shore beach profile is tightly related to the evolution of the coastline in both small and large time scales. Bathymetry changes in extreme maritime events can also have important effects on coastal infrastructures such as geotechnical failures of foundations or the modification of the incident wave conditions towards a more unfavourable situation.</p><p>The available strategies to study the evolution of beach profiles can be classified in analytical, physical and numerical modelling. Analytical solutions are fast, but too simplistic for many applications. Physical modelling provides trustworthy results and can be applied to a wide variety of configurations, however, they are costly and time-consuming compared to analytical strategies. Finally,  numerical approaches offer different balances between cost and precision depending on the particular model.</p><p>Some numerical models provide greater precision in the beach profile evolution, but incurring in a prohibitive computational cost for many applications. In contrast, the less expensive ones assume simplifications which do not allow to correctly reproduce significant phenomena of the near-shore hydrodynamics such as wave breaking or undertow currents, neither to predict important features of the beach profile like breaker bars.</p><p>In this work, a new numerical model is developed to reproduce the main features of the beach profile and hydrodynamics while maintaining an affordable computational cost. In addition, it is intended to reduce to the minimum the number of coefficients that the user has to provide to make the model more predictive.</p><p>The model consists of two main modules. Firstly, the already existing 2D RANS numerical model IH2VOF is used to compute the hydrodynamics. Secondly, the sediment transport model modifies the bathymetry according to the obtained hydrodynamics. The new bathymetry is then considered in the hydrodynamic model to account for it in the next time step.</p><p>The sediment transport module considers bedload and suspended transports separately. The former is obtained with empirical formulae. In the later,the distribution of sediment concentration in the domain is obtained by solving an advective-diffusive transport equation. Then, the sedimentation and erosion rates are obtained along the seabed.<br>Once these contributions are calculated, a sediment balance is performed in every seabed segment to determine the variation in its level.</p><p>With the previously described strategy, the resulting model is able to predict not only the seabed changes due to different wave conditions, but also the influence of this new bathymetry in the hydrodynamics, capturing features such as the generation of a breaker bar, displacement of the breaking point or variation of the run-up over the beach profile. To validate the model, the numerical results are compared to experimental data.</p><p>An important novelty of the present model is the computational effort required to perform the simulations, which is significantly smaller than the one associated to existing models able to reproduce the same phenomena.</p>

scholarly journals Study of Beach Erosion and Evolution of Beach Profile Due to Nearshore Bar Sand Dredging

2015 ◽  
Vol 116 ◽  
pp. 285-292 ◽  
Author(s):  
Duc Thang Chu ◽  
Gen Himori ◽  
Yuki Saito ◽  
Trong Vinh Bui ◽  
Shin-ichi Aoki
Keyword(s):  
Beach Erosion ◽  
Beach Profile

scholarly journals ANALYSIS ON PERFORMANCE OF THE EMERGENCY NOURISHMENT PROJECT AT WEST BEACH OF BEIDAIHE, CHINA

2011 ◽  
Vol 1 (32) ◽  
pp. 98 ◽  
Author(s):  
Yanxiong Yang ◽  
Jiabo Zhang ◽  
Cuiping Kuang ◽  
Yu Zhang ◽  
Lulu He ◽  
...  
Keyword(s):  
Water Conservation ◽  
Large Scale ◽  
Beach Nourishment ◽  
Beach Erosion ◽  
Profile Measurement ◽  
Beach Profile ◽  
Survey Period ◽  
Before And After ◽  
Conservation Projects ◽  
Large Scale Project

Beach erosion is prevalent on China’s 18,000 km-long coastline, which has been aggravating due to urban development, river-damming and soil and water conservation projects since late 1970s. Beach erosion threatens the health of beaches of bathing places throughout the world. An effective way to defense the beach erosion is beach nourishment. In this paper, the study on an experimental beach nourishment project, which was conducted to provide data and experience for a large-scale project, was detailed. Field survey was conducted to study the performance of the project. Before and after the project, 8 monitoring profiles had been kept measuring along with the berm positions. The beach profile measurement indicates that after a little retreat the beach got relatively equilibrium, while the berm measurement shown a broadened intertidal zone getting stable eventually. In a word, the filled beach was eroded a little but finally got relatively stable in the survey period.

scholarly journals A Simple Nozzle-Diffuser Duct Used as a Kuroshio Energy Harvester

Processes ◽  
2021 ◽  
Vol 9 (9) ◽  
pp. 1552
Author(s):  
Po-Hung Yeh ◽  
Shang-Yu Tsai ◽  
Wei-Ren Chen ◽  
Shing-Nan Wu ◽  
Meng-Chang Hsieh ◽  
...  
Keyword(s):  
Energy Demand ◽  
Energy Harvester ◽  
Normal Wave ◽  
Sea Surface ◽  
Ocean Current ◽  
Ansys Fluent ◽  
Wave Condition ◽  
Storm Wave ◽  
Wave Conditions ◽  
The Kuroshio

In response to the increasing energy demand in Taiwan and the global trend of renewable energy development, Kuroshio energy is a potential energy source. How to extract this invaluable natural resource has then become an intriguing and important question in engineering practices. This study reported the results of a feasibility study for a nozzle-diffuser duct (NDD) as the Kuroshio currents energy harvester. The computational fluid dynamics (CFD) software ANSYS Fluent was employed to calculate the drag and added mass coefficients of the duct anchored to the seabed. Those coefficients were further imported into Orcaflex to simulate the motion of the duct under normal and storm wave conditions. Results showed that the duct was stable 25 m below the sea surface under normal wave conditions. When the wave condition changed to storm waves, the duct needed to dive into at least 90 m below the sea surface to regain its stability and obtain high power take-off (PTO). An optimal design nozzle-diffuser-duct was reported, and a PTO peak of 15 kW was expectable in the Kuroshio currents. Once a suitable offshore platform can be developed with sixty-six NDDs, a Megawatt Kuroshio ocean current power generation system is feasible in the near future.

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