scholarly journals ON THE EFFECT OF ARMOUR BLOCK FACING ON THE QUANTITY OF WATTE OVERTOPPING

1968 ◽  
Vol 1 (11) ◽  
pp. 55
Author(s):  
Naofumi Shiraishi ◽  
Atusushi Numata ◽  
Taiji Endo
Keyword(s):  
Wave Energy ◽  
Field Observation ◽  
Storm Surges ◽  
Design Criterion ◽  
Characteristic Functions ◽  
Crown Height ◽  
Wave Overtopping

Japan, surrounded by sea, is constantly threatened by storm surges and beach erosions, for which protection works are being vigorously undertaken. As a measure for protection, facings of various armour blocks have come to be used for the seawalls and embankments. This is a skillful utilization of characteristic functions of armour blocks to dissipate and absorb wave energy effectively. However, systematic experiments and studies on this subject have been conducted only in very few cases. This paper treats of the effect of the facing of armour blocks on wave overtopping by comparison of the quantity of waves topped over the vertical seawal] with facing and that of without facing. Furthermore, this paper attempts to compare the results of the field observation and the experiments on the quantity of wave overtopping. Based on these data, the authors present a design criterion of the crown height of seawall with armour block facing.

scholarly journals Effect of Variations in Water Level and Wave Steepness on the Robustness of Wave Overtopping Estimation

2020 ◽  
Vol 8 (2) ◽  
pp. 63
Author(s):  
Nils B. Kerpen ◽  
Karl-Friedrich Daemrich ◽  
Oliver Lojek ◽  
Torsten Schlurmann
Keyword(s):  
Water Level ◽  
Wave Spectrum ◽  
Water Environment ◽  
Physical Modelling ◽  
Storm Surges ◽  
Water Levels ◽  
Coastal Protection ◽  
Wave Steepness ◽  
Wave Overtopping

The wave overtopping discharge at coastal defense structures is directly linked to the freeboard height. By means of physical modelling, experiments on wave overtopping volumes at sloped coastal structures are customarily determined for constant water levels and static wave steepness conditions (e.g., specific wave spectrum). These experiments are the basis for the formulation of empirically derived and widely acknowledged wave overtopping estimations for practical design purposes. By analysis and laboratory reproduction of typical features from exemplarily regarded real storm surge time series in German coastal waters, the role of non-stationary water level and wave steepness were analyzed and adjusted in experiments. The robustness of wave overtopping estimation formulae (i.e., the capabilities and limitations of such a static projection of dynamic boundary conditions) are outlined. Therefore, the classic static approach is contrasted with data stemming from tests in which both water level and wave steepness were dynamically altered in representative arrangements. The analysis reveals that mean overtopping discharges for simple sloping structures in an almost deep water environment could be robustly estimated for dynamic water level changes by means of the present design formulae. In contrast, the role of dynamic changes of the wave steepness led to a substantial discrepancy of overtopping volumes by a factor of two. This finding opens new discussion on methodology and criteria design of coastal protection infrastructure under dynamic exposure to storm surges and in lieu of alterations stemming from projected sea level rise.

MECHANISM AND COUNTERMEASURES OF WAVE OVERTOPPING FOR LONG-PERIOD SWELL IN COMPLEX BATHYMETRY

2012 ◽  
Vol 1 (33) ◽  
pp. 45
Author(s):  
Hiroaki Kashima ◽  
Katsuya Hirayama
Keyword(s):  
Deep Water ◽  
Wave Energy ◽  
Spatial Relationship ◽  
Wave Transformation ◽  
Wave Overtopping ◽  
Long Period ◽  
Wave Characteristics ◽  
Water Region ◽  
Wave Heights ◽  
Shallow Water Region

Recently, coastal disasters due to long-period swells induced by heavy storms and catastrophic typhoons have increased at Japanese coasts and harbors. Long-period swells are more susceptible to the bottom bathymetry of the offshore deep water region and their wave heights locally increase due to the concentration of wave energy caused by the complex bottom bathymetry in the relatively shallow water region. In addition, the wave overtopping rate may increase due to the long waves in front of the seawall induced by the long-period swells. However, the spatial relationship between wave characteristics and wave overtopping discharges in the complex bathymetry are not well known owing to a lack of detailed measurements. In this study, model experiments were conducted by using a large basin to investigate the spatial characteristics of wave transformation and wave overtopping focusing on the heavy wave overtopping damages caused by the arrivals of long-period swells at the Shimoniikawa Coast in 2008. Effective countermeasures against wave overtopping are also discussed based on their characteristics.

scholarly journals INFLUENCE OF CROWN-WALL ON WAVE OVERTOPPING PROBABILITY AND PROBABILITY DISTRIBUTION OVER A SEAWALL

2018 ◽  
pp. 70
Author(s):  
Jiayue Gu ◽  
Xin Hu ◽  
Shuguang Liu ◽  
Quanhe Ju
Keyword(s):  
Design Method ◽  
Storm Surges ◽  
Wave Overtopping ◽  
Individual Volume ◽  
The Pacific ◽  
Individual Wave ◽  
The Pacific Ocean ◽  
Engineering Measure ◽  
Overtopping Probability ◽  
The Stability

In the past decades, the crest height of the seawall was determined by the allowable average wave overtopping rate q. Franco (1994) concluded that individual wave overtopping，particularly the maximum individual volume, provided a better design method than q, considering the stability of the seawall and the safety of vehicles and people along the coastal area protected by the coastal defense structures. Shanghai, located on the west bank of the Pacific Ocean, is quite sensitive to the risk of storm surges and violent wave overtopping. The crown-wall serves as an engineering measure to reduce the wave overtopping effectively.

scholarly journals ROUGHNESS FACTOR FOR MULTI-LAYER ARMOUR AS OVERTOPPING ESTIMATOR

2020 ◽  
pp. 25
Author(s):  
Leopoldo Franco ◽  
Yuri Pepi ◽  
Stefano de Finis ◽  
Verdiana Iorio ◽  
Giorgio Bellotti ◽  
...  
Keyword(s):  
Structural Characteristics ◽  
Storm Surges ◽  
Random Wave ◽  
Roughness Factor ◽  
Coastal Structures ◽  
Wave Overtopping ◽  
Wave Flume ◽  
Physical Model Tests ◽  
Rubble Mound ◽  
Rubble Mound Breakwaters

Nowadays one of the most challenging problem for engineers is to adapt existing coastal structures to climate changes. Wave overtopping is highly sensitive to the increasing extreme water depths due to higher storm surges coupled with sea level rise. One way to face these problems for rubble mound breakwaters is to add one or more layers to the existing armour. Prediction of wave overtopping of coastal structures is presently obtained from empirical formulae in EurOtop (2018). For the case of overtopping over multi-layer armour, no validated method exists, so prediction must be based upon assumptions and judgement, with related uncertainties. This study is focused on the effects of different types of armour, the number of layer and other structural characteristics on the roughness factor f. The main effects of porosity and roughness will be investigated. This paper analyzes the results of several new physical model tests of different rubble mound breakwaters reproduced at the new medium scale random wave flume of the Department of Engineering of Roma Tre University.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/8cOdqkqQ-9s

Wave overtopping and splash-up at seawalls with bullnose

2020 ◽  
Vol 20 (3) ◽  
pp. 333-342
Author(s):  
Le Hai Trung ◽  
Dang Thi Linh ◽  
Tang Xuan Tho ◽  
Nguyen Truong Duy ◽  
Tran Thanh Tung
Keyword(s):  
Storm Surges ◽  
Model Tests ◽  
Scale Model ◽  
Small Scale ◽  
Wave Overtopping ◽  
Run Up ◽  
Coast Of Vietnam ◽  
Small Scale Model ◽  
Wall Interactions

Seawalls have been erected to protect hundreds of towns and tourism areas stretching along the coast of Vietnam. During storm surges or high tides, wave overtopping and splash-up would often threaten the safety of infrastructures, traffic and residents on the narrow land behind. Therefore, this study investigates these wave-wall interactions via hydraulic small scale model tests at Thuyloi University. Remarkably, the structure models were shaped to have different seaward faces and bullnoses. The wave overtopping discharge and splash run-up height at seawalls with bullnose are significantly smaller than those without bullnose. Furthermore, the magnitude of these decreasing effects is quantitatively estimated.

Field observation and numerical simulation of past and future storm surges in the Bay of Bengal: case study of cyclone Nargis

2014 ◽  
Vol 75 (2) ◽  
pp. 1619-1647 ◽  
Author(s):  
Khandker Masuma Tasnim ◽  
Tomoya Shibayama ◽  
Miguel Esteban ◽  
Hiroshi Takagi ◽  
Koichiro Ohira ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Bay Of Bengal ◽  
Field Observation ◽  
Storm Surges ◽  
Cyclone Nargis

scholarly journals Numerical Simulations of the Hydraulic Performance of a Breakwater-Integrated Overtopping Wave Energy Converter

2019 ◽  
Vol 7 (2) ◽  
pp. 38 ◽  
Author(s):  
Giuseppina Palma ◽  
Sara Mizar Formentin ◽  
Barbara Zanuttigh ◽  
Pasquale Contestabile ◽  
Diego Vicinanza
Keyword(s):  
Wave Energy ◽  
Wave Reflection ◽  
Energy Converter ◽  
Wave Overtopping ◽  
Energy Capture ◽  
Multifunctional Device ◽  
Average Wave ◽  
Sloping Plate ◽  
The Waves ◽  
Harbour Area

OBREC is the acronym that stands for Overtopping Breakwater for Energy Conversion. It is a multifunctional device aimed to produce energy from the waves, while keeping the harbour area protected from flooding. In this paper, the inclusions of a berm to reduce wave reflection, the shape of the sloping plate to maximise wave overtopping and the reservoir width and the crown wall shape to maximise wave energy capture while keeping the harbour safety were analysed to optimize the hydraulic and structural performances of the device. Several configurations were numerically investigated by means of a 2DV RANS-VOF code to extend the results already obtained during previous experimental campaigns. The wave reflection coefficient, the average wave overtopping flows and the wave loadings along the structure are computed, compared with existing formulae and discussed with reference to the OBREC prototype installed in the Port of Naples.

scholarly journals Long-Term Assessment of an Innovative Mangrove Rehabilitation Project: Case Study on Carey Island, Malaysia

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Shervin Motamedi ◽  
Roslan Hashim ◽  
Rozainah Zakaria ◽  
Ki-Il Song ◽  
Bakrin Sofawi
Keyword(s):  
Wave Energy ◽  
Ph Value ◽  
Storm Surges ◽  
Coastal Protection ◽  
Coastal Structures ◽  
Mangrove Seedlings ◽  
Salinity Index ◽  
Mangrove Rehabilitation

Wave energy and storm surges threaten coastal ecology and nearshore infrastructures. Although coastal structures are conventionally constructed to dampen the wave energy, they introduce tremendous damage to the ecology of the coast. To minimize environmental impact, ecofriendly coastal protection schemes should be introduced. In this paper, we discuss an example of an innovative mangrove rehabilitation attempt to restore the endangered mangroves on Carey Island, Malaysia. A submerged detached breakwater system was constructed to dampen the energy of wave and trap the sediments behind the structure. Further, a large number of mangrove seedlings were planted using different techniques. Further, we assess the possibility of success for a future mangrove rehabilitation project at the site in the context of sedimentology, bathymetry, and hydrogeochemistry. The assessment showed an increase in the amount of silt and clay, and the seabed was noticeably elevated. The nutrient concentration, the pH value, and the salinity index demonstrate that the site is conducive in establishing mangrove seedlings. As a result, we conclude that the site is now ready for attempts to rehabilitate the lost mangrove forest.

scholarly journals RESEARCHES ON SEA-WALLS

1970 ◽  
Vol 1 (12) ◽  
pp. 88
Author(s):  
S. Nagal
Keyword(s):  
Incident Wave ◽  
Wave Energy ◽  
Precast Concrete ◽  
Recent Decade ◽  
Point Of View ◽  
Industrial Firms ◽  
Wave Overtopping ◽  
Port Facilities ◽  
Sea Wall ◽  
Incident Wave Energy

In the recent decade, very wide areas of sea where the depths of water are from several meters to ten meters or more during storms have been reclaimed for industrial firms and port facilities in many places in Japan As the incident wave energy in such cases is very large at the sea-walls, the protection of the reclaimed lands from wave overtopping by the conventional sea-walls of vertical type or composite-slope«and-berai type is generally impossible from an economical point of view In Japan a special type of sea-wall, which is of such a type that a rubble-mound covered with specially shaped precast concrete armor blocks is built in front of the sea-wall to absorb most of the incident wave energy, has been constructed to protect the reclaimed lands from wave overtopping Most of the seawalls have been proved satisfactory after passing of typhoons over or near the sea-walls The design of the sea-walls is presented here in by showing the comparisons between the experiments and prototypes during typhoons.

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