Asian and Pacific Coasts 2011

The following sections are included:

• Contents

• PREFACE

The coastal zone, or the transition region between land and ocean, is of great importance because of its economic, security and recreational utility and its impact on contiguous human settlements and ecosystems. Hydrodynamic and biogeochemical processes of different scales, their interactions and climate-related changes such as eustatic sea level rise lead to continuous evolution of coastal circulation, water quality and land cover. In addition, anthropogenic activities weaken natural beach-defense mechanisms and geomorphic stability, thus making coastal communities vulnerable to natural disasters such as hurricanes and tsunamis. Effluent releases to coastal areas affect water quality and impair marine life. In conflict zones, underwater mines are a weapon of choice and their burial in sediments is an impediment for detection and safe removal of mines. Further offshore, density stratification plays an important role, thus supporting internal waves, meso-scale eddies and turbulent mixing. All these application areas are entwined with fundamental physical, geological, chemical and biological processes of the coastal zone, the understanding of which is imperative for making informed decisions on coastal zone management.

The initial tidal energy technologies deployed to date have had limited success in demonstrating the cost effectiveness of generating power from tidal flows. The bench mark to achieving commercial acceptance is linked to the cost of energy associated with off-shore wind power. Due to the increased costs of the engineering systems adopted within these ‘first mover’ tidal technologies, this makes it difficult for these systems to demonstrate cost competitiveness in an energy market dominated by lower cost fossil fuels. In order for tidal systems to become cost competitive, greater efforts need to be made to reduce system capital and maintenance costs.

In this paper, the following are analyzed, the formation, the recent development, the long term evolution trends and the exploit of the radial sand ridges at the South Yellow Sea, China. A radial tidal current field is formed from the interactions between two tidal systems. The radial tidal current pattern is regarded as the driven force to generate and maintain this morphological feature. An analysis on the tide, wave and morphological changes of the tidal channels and sand ridges was carried out. The reclamation of Xiaomiaohong tidal flat and the construction of the artificial island for Yangkou Harbor provided engineering practice. Thus we claim that the key point for a consistent development of the radial sand ridges is to limit human interference, in the form of land reclamation on the tidal flat and the exploit of harbor development, so as to adapt to the natural evolution of hydrodynamic conditions and morphological changes.

This paper introduces projection of future wave climate and analysis of differences between present and future ocean wave climate using the data of high-resolution atmospheric General Circulation Model and a global wave model. Secondly, a stochastic typhoon model for estimating characteristics of typhoons in both present and future climate conditions is described. Differences of statistical characteristics between present and future typhoons estimated from the GCM projections are taken into account in the stochastic model of future typhoons. Finally, the failure probability of seawalls is briefly described concerning the effects of sea level rise and waves.

This paper describes several methods to incorporate wave height increase due to climate change in the performance-based design of a caisson breakwater and their application to the East Breakwater of the Port of Hitachinaka in Japan. When wave height increase was not included, the performance-based design methods calculated the same caisson width as that of the constructed breakwater, partly validating the consistency with the conventional deterministic methods. Wave height increase dictates an increase in caisson width of about 1.5 m and 0.5 m for linear and parabolic increases, respectively, which are about 6.8% and 2.3% of the present caisson width of 22 m. Finally, it is recommended that the caisson breakwater be designed using the projected wave height 30 years from construction, if the deterministic method is used and climate change impacts are to be taken into account.

When a solitary wave (a model of tsunami in the nearshore shallow water) impinges on a reflective vertical wall, it can take the formation of Mach reflection (a geometrically similar reflection from acoustics). The mathematical theory predicts that the amplification at the reflection is not twice, but four times the incident wave amplitude. Evidently, this has an important implication to engineering design practice. Our laboratory experiments verify detailed features of the Mach reflection phenomenon, whereas contradict the theory in terms of the maximum four-fold amplification: the maximum amplification observed in the laboratory was 2.9, instead. The reason for the discrepancy is discussed. In addition, we show that a tsunami along the reflective wall can reach higher than the maximum solitary wave height. Once the wave breaking happens along the wall, the substantial increase in water-surface slope results along the wave crest away from the wall.

At 14:46 local time on March 11, 2011, a magnitude 9.0 earthquake occurred off the coast of northeast Japan. This earthquake generated a tsunami that struck Japan as well as various locations around the Pacific Ocean. With the participation of researchers from throughout Japan, joint research groups conducted a tsunami survey along a 2000 km stretch of the Japanese coast. More than 5400 locations have been surveyed to date, generating the largest tsunami survey dataset in the world. The maximum run-up height measured to date was 40.4 m, resulting in the catastrophic destruction of towns and cities.

On March 11, 2011, a large earthquake of magnitude 9.0 took place, generating a tsunami that caused a severe damage to the east coast of Japan. Field surveys were performed to know tsunami inundation heights and disasters in Iwate, Miyagi, Fukushima, Ibaraki and Chiba prefectures. The results of these surveys are reported. Inundation heights were more than 10 m in the north part of Miyagi, 5 to 10 m along the coast of Sendai Bay and around 5 m in Ibaraki and Chiba. Buildings, including reinforced concrete structures, were washed away and ships were stranded in land. Coastal structures such as dikes and coastal forests also suffered extensive damage. Possible evacuation measures are also discussed based on the observations.

A huge earthquake occurred in the Pacific Ocean off Tohoku area, Japan, at 14:46 local time on March 11, 2011. Tsunamis due to this earthquake were the maximum in Japanese history and caused serious damage on extensive areas of Tohoku. In this study, field survey of suffering appearances due to tsunamis was carried out targeting 20 areas along coasts of Iwate and Miyagi Prefectures focusing on damage of coastal structures and effects of topography. As a result of survey, it was found that design conditions for coastal structures should be decided considering topography, especially areas of low-lying land, behind these structures.

In the immediate aftermath of the 2011 Tohoku earthquake, we deployed a post-tsunami reconnaissance in the Sanriku Coast, Japan, where destructive damages caused by tsunami waves were demonstrated, as well as from the historical events. Significant land subsidence was observed with the ground level of harbor dock being inundated at high tide level after the earthquake. Damages on coastal structures, such as harbor jetty, seawall and breakwater, were also confirmed. Failure pattern of these structures exhibits a complex feature with respect to the tsunami height, current velocity and wave direction, the structure layout and its armoring effort.

We proposed a rapid method for forecasting tsunami runup on the coasts combining 2-D numerical model and 1-D analytical runup theory. In the first step, the 2-D numerical simulations of tsunami generation and propagation are performed assuming impermeable boundary conditions of a 5-10m depth at the last sea points (equivalent to a wall). Then the time series of the water oscillations on the wall are used to calculate the runup heights using the analytical integral expression following from 1-D theory. The feasibility of this approach was validated against the disastrous 2011 Great East Japan Earthquake Tsunami. We have demonstrated that the proposed approach is more reasonable and rapid method of forecasting than complicated coastal inundation models.

In this study, initial wave field of the 2011 Tohoku tsunami was estimated by using waveform inversion method. And numerical simulations of the 2011 Tohoku tsunami were performed in order to analyze the propagation characteristics over the Pacific Ocean and to verify the waveform inversion method. Numerical results were compared with observed data of NOAA's DART buoy system and DONET system of JAMSTEC.

In the present study the effect of bathymetry near the south-west sea area of Korea on the propagation of 2011 North-East Japan Tsunami is analyzed based on the numerical simulation using the finite difference dispersion-correction model. It is found that the bathymetry from the source to Korean Peninsula, such as Nankai Trough, Ryukyu Islands and the topographical lens in the East China Sea, plays an important role to reduce the tsunami height along the south coast of Korea. The mechanism involved in the transformation of tsunamis over those topographies is discussed.

In tsunami modeling not all of physical phenomena, which occurs in reality, can be considered, especially with respect to source description and inundation. Empirical relations to describe earthquake deformations found in the literature differ considerably amongst each other, and so therefore does the subsequent inundation model results. In this paper it is tested if simplified source descriptions, still based on released earthquake energy, might lead to the same quality of inundation results. The test case selected is the 11 March 2011 Great East Japan Tsunami has been used to test such simplified source descriptions. The inundation modeled for four cities have been compared with observations. The results suggest that a simplification of the source description does not lead to lower quality in inundation modeling.

The 2011 East Japan Tsunami yielded a wealth of quality data and information. Here we focus on the waveform data recorded with the offshore gages at three locations along the east-to-west transect from the city of Kamaishi (39°16'N 141°53'E). The recorded data show the coherent waveform: the formation of a narrow spiky wave riding on the broader tsunami base at its rear side. This waveform resulted in the gradual initial rise and the strong second-stage runup, followed by the rapid drawdown. Our analysis shows that the linear water-wave theory can predict approximately the shoaling evolution, although some discrepancies in its propagation speed and amplification exist. Consequences of the tsunami waveform to the observed tsunami damage and human losses are discussed.

Jiangsu coastal zone is located in the center of coastal area of eastern China. Recently, “The Developing Plan for Jiangsu Coastal Zone” was approved by the Chinese Central Government, indicating that the development of Jiangsu coastal zone has been upgraded to be part of national development strategy. According to the Plan, about 1,800 km² of Jiangsu tidal flat is to be reclaimed during 2009-2020. A master plan of reclamation of Jiangsu tidal flat is made to ensure the reclamation in a scientific, comprehensive and efficient way. The main contents of the master plan, including the guidelines and principles of reclamation, the spatial layout of the reclaimed area, the procedure of implementation, the necessary construction of ancillary infrastructures as well as the environmental protection and financial safeguard measures for the reclamation, are presented in this paper.

After 2005 there is a sharply increase in the quantities of beach nourishment in China. In this paper the beach nourishment projects in China are reviewed and discussed with respect to the project history, distribution, types, objectives, design, and evaluation. The designs and evaluations of two beach nourishment projects in Qinhuangdao are introduced briefly to provide a feature of current beach nourishment in China. It is inferred from the project review that the beach nourishment in China is on its beginning and the projects are initiated spontaneously by local governments and agencies with different technologies for economic benefits, better city image and the convenience of citizens. In the light of the review of beach nourishment projects some future prospects of the beach nourishment industry of China are proposed.

Coral Reef Islands of Spermonde (Sangkarang) extends widely in southwest of South Sulawesi Province composed of coral reef islands which are functioning as natural breakwaters, and as coral reef islands providing biological production. This paper aims to describe some problems of coastlines of the islands due to exceeding exploitation from view points of morphogenetics and morphodynamics, and to prepare a policy in promoting the islands as tourist destinations. There is anxiety that once the islands have degraded, the west coast will be threatened by incoming waves during west monsoon. The proper utilizations of the islands might be considered and promoted as sustainable tourism, by which Regional governments should be able to identify potencies of its natural characteristics and cultural peculiarity to formulate marketable tourist destinations and related facilities. The discussion will arrive at the need of a strong networking for cooperation, partnership, collaboration with various stakeholders who are accessible to the resources, and coordination among surrounding regional governments for smooth access and supporting needs. If the nature of the Spermonde Islands have been understood and completed with clear understanding and proper formulation to manage sustainable tourism, it will bring the area to be attractive as tourist destinations, from where the potency to maintain the islands will be prospective.

The Jiangsu coast area is controlled by the East China Sea progressive tidal wave and the Southern Yellow Sea rotary tidal wave. The two tidal wave systems coming from the opposite direction converge near the middle of the Radiative Sandy Ridge. Under this special hydrodynamic condition, a large geomorphologic dynamic response system formed in the Tiaozini sandbank which is named Erfenshui water-dividing beach ridge. Using in situ measurements and some remote sensing satellite images, this paper discusses the geomorphologic characteristics, sedimentary characteristics, hydrodynamic characteristics and historical evolution pattern of the Erfenshui water-dividing beach ridge. Its ridge width is about 1km and the average height is about 0.5 m. The slope is about 0.64%. It separates the Tiaozini sandbank into two parts. The surface sediment type is mostly sandy silt. The ebb average current velocity is larger than the flood during the measurement period. The maximum velocity occurred at the surface layer and decreased gradually from the surface to bottom. The flood suspended sediment concentration is greater than the ebb. The maximum sediment concentration occurred at the bottom, which increased gradually from surface to bottom. The average sediment discharge of per unit width is 1.30 kg/m³ during the flood and is 1.07 kg/m³ during the ebb, which shows that the sediment source is sufficient and the Erfenshui water-dividing beach ridge is in the deposition environment. The location of the Erfenhui sandy beach ridge is not fixed. It moved from south to north about 14.5 km because of the typhoon storm surge in 1974 and moved from north to south about 6 km because of the coastal reclamation.

Many different sediment transport formulas are available to estimate geomorphic changes in river and coastal environments. However, there have been few publications in the literature dealing primarily with sediment transport processes associated with tsunami waves. It is desirable to evaluate the performances of these existing formulas in modeling shoreline erosion due to tsunamis. The main objective of this study is to simulate, using six classical sediment transport formulas, the sediment transport under the action of solitary waves or tsunami-like waves and compare the numerical results with available measured data. By comparing the simulated and measured changes of bed profiles, the suitability of these models to simulate the tsunami induced shoreline changes is discussed. Our comparisons show that (i) the results obtained using different sediment transport models often differ drastically from each other, and (ii) special care need to be taken when selecting model parameters for large waves which may generate bed shear stresses much larger than those normally encountered in open channel flows. The findings reported here will be useful for researchers working on tsunami hazard mitigation problems.

On the Hamamatsu-Shinohara coast facing the Pacific Ocean, beach has been severely eroded, resulting in the shoreline recession of 210 m between 1962 and 2004. As a measure against beach erosion, beach nourishment using a mixture of sand and gravel was begun in 2005. Since then, 3.5×10⁵ m³ of sediment was supplied to the coast. Although the foreshore was widened by the beach nourishment, not only sand but also gravel was rapidly transported downcoast, resulting in the change in grain size of the beach material. In this study, the changes in the quality of the beach in terms of the grain size and transport process of gravel were investigated by field observation. Beach nourishment using coarser materials is effective for the shore protection, but it must be carefully used because of change in grain size.

The Hirota ruins are located in Minamitane Town on Tanegashima Island, 25 km south of Kyushu Island. The coastal sand dune containing these ruins has remained stable for approximately 1,400 years. In September 2005, Typhoon No. 14 passed very close to Tanegashima Island and the sand dune of the Hirota coast was eroded by storm waves, exposing the ruins. The causes of damage to the ruins were investigated using field data. It was found that the primary cause was the attack of the storm waves and the secondary cause was the truncation of the seawall at the north end.

The west coast of Korean Peninsula has large tidal range about 9 to 4 meters. And there are large scale tidal flat beach. Recently, many sandy beaches connecting the tidal flat beach make use of the human resorts, and severe beach erosion has been occurred since 1980s due to the effect of constructing the facilities of resorts. Particularly, the erosion of the sandy beach connecting the tidal flat beach has taken place with some kind of the difference mechanism to the traditional theory of beach erosion; that is thought of the swell surging on the top of the slope face of sandy beach that is connected the large scale tidal flat beach. Considering the like those of hydraulic phenomena, hydraulic model test and field experiment carried out for the purpose of the beach nourishment. It was found that the nourishment profile at the large scale tidal flat beaches are dominated mainly the scale of off shore return flow along to the slope face of the beach. That is supposed to be caused by the swell surging in case of high tides.

The long-term topographic changes of the Tenryu River delta were predicted using the contour-line-change model, in which changes in grain size are taken into account. Given the annual discharge of sediment with three grain sizes, the recovery of the delta topography and the effect of nourishment on the nearby coast were predicted. Under the hypothetical condition that no coastal structures had been constructed along the coast, the effect of artificial sand supply from the river mouth was studied. The model was applied to the coast with a 10 km length extending on each side of the river mouth, and the beach changes up to 100 years from the present were predicted.

A 1D numerical model is reported that has the capability of modeling solitary wave runup and rundown an erodible bed. We couple the highly nonlinear and weakly dispersive Boussinesq equations with a sediment transport module and morphological evolution module to study the sediment transport and morphological changes under solitary waves. The combined model is validated using available laboratory experiments on solitary waves attacking sandy beaches.

Significant coastal erosion of the Nandu River Delta in Hainan Province has occurred in recent decades, caused by the compound actions of natural factor, such as the waves, tides, storm surges, and rising sea levels, and human activities like reservoir construction and river dredging. In this study, the stability of the shore was analyzed based on the measured depth from March 2008 to March 2009 and the charts of the Nandu River Delta during the years 1984 to 2007. Several evaluation factors, such as annual erosion rate of shoreline, down-cutting rate of beach surface, and erosion rate of the shoreline, were adopted to calculate erosion hazard. The results showed that the eastern, northern, and western coasts were in a state of serious erosion or erosion and silting. Additionally, the results of hazard analysis of the coasts using the coastal erosion hazard evaluation index system showed that the coasts were all at the medium hazard level.

Severe erosion is experienced around the Nile delta promontories. While the highest rate of erosion occurs around Rosetta promontory, less significant erosion rates are observed around Damietta promontory and accretion is also observed around the east side of the Damietta promontory. This accretion mainly forms sand spit and is still growing toward the south-east. The main goal of this study is to monitor the large scale morphology changes around Damietta promontory and to investigate the growing mechanism of sand spit through comparisons of shoreline profiles semi-automatically extracted from the land-sat data set. Extracted shorelines are quantitatively investigated based on the linear regression technique as well as the empirical orthogonal function analysis.

The Nebukawa coast is a typical shingle beach located on the east coast of Izu Peninsula, and therefore, its stability was believed to be high. However, the coast has been eroded in recent years. To investigate the cause, the shoreline changes were investigated. It was found that a large-scale avalanche of earth and rocks and landslide were triggered in this area by the 1923 Kanto Earthquake, and a large amount of gravel was supplied to the coast, forming shallow contours protruding offshore. Since then, this coastline has receded under the action of northward longshore sand transport. Thus, the beach erosion of this coast is closely related to the long-term beach changes after the earthquake.

On the Akashi coast facing the Pacific Ocean, beach nourishment using gravel with grain sizes ranging between 2.5 and 13 mm was carried out. Beach changes were monitored by taking photographs from several fixed points. It was found that medium-grain-sized sand and fine sand were deposited on the gravel beach under calm wave conditions, whereas the nourishment gravel was transported onshore and deposited in front of the seawall under storm wave conditions. The deposition of fine and medium sand on the gravel layer under calm wave conditions was successfully explained on the basis of the increases in the equilibrium slopes of fine and medium sand due to the large percolation effect of the gravel layer using the contour-line-change model considering grain size changes.

A numerical model for predicting three-dimensional beach evolution to sandy beach with hard sea bottom such as shore reef was developed. The change in the water depth was considering the thickness of sand layer over hard bottom, and then the exposing and burring of shore reef were reproduced. Firstly, a model test associated with the morphodynamic at an idealized pocket beach with exposed shore reef area was carried out. Secondary, the numerical model was applied to morphodynamics around a small fishery port surrounded in the shore reef area, which is suffering from deposition due to waves and nearshore currents. Finally, the applicability of the model was discussed.

The beach nourishments have been carried out. Especially, the method using coarser sand has been noticed in Japan. In this study, laboratory experiments were conducted on the performance of beach nourishment of three types of grain size sand on a fine sand beach. The nourished sands were placed at near breaking point. After that the three types of irregular wave were acted. The changes of the beach profile were measured using a laser displacement meter.

Understanding of coastal change during the short and medium-term is necessary for proper management of coastal resources, particularly in light of widespread coastal retreat. In this study, based on analysis of field data and sea maps, the characteristic of the northern bank, Hangzhou bay (NBHZB) is of accretion in winter half year and erosion in summer half year, respectively, due to the impacts of seasonal wave climate actions. However, coastal morphodynamic processes during typhoon actions could be described as that the crest of submarine bar was cut down, runnel was filled up and submarine platform was eroded into several similar shape of small bar-runnel. In addition, coastal erosion had drastically occurred along NBHZB in recent 20 years, which could be induced by the abrupt decreased sediment from Yangtze River.

This study deals with the simulation of topographical changes conducted by image analysis, field survey and image data based on point camera observation in order to examine the dynamic process of topographical changes in formation, maintenance and disappearance of Chiringa-shima Island tombolo, which emerges between the Ibusuki beach and Chiringa-shima Island in Kagoshima Prefecture, Japan. This study was conducted to develop practicable point camera observation in the field for a long time by using a general digital camera and a solar panel. The point camera image data was converted into orthophotos that examine dynamic process of topographical changes Chiringa-shima Island tombolo throughout a year. The tombolo was found to be unique in that it has daily and yearly changes in formation.

The causes of sediment loss at Golden Beach in Hong Kong have been studied by analysis of historical shorelines and numerical modeling of sediment transport processes. Analysis of historic shorelines from 1994 to 2008 shows erosion of up to 2m/yr at the eastern end and up to 1m/yr at the western end of the beach. The model results show that Golden Beach is very oblique to the prevailing wave climate. This results in high longshore sediment transport gradients along the beach (given that there is no sediment supply past the marina entrance to the beach). Thus, sand placed at Golden Beach is eroded very quickly due to the prevailing wave climate and beach configuration. This mechanism for erosion was confirmed in simulations with the shoreline evolution model and two-dimensional coastal area models.

The morphodynamics of sandy beaches along the coast of Yueliang Bay which is to the north of the Tonggu Hill National Nature Reserve (THNNR), Northeastern Hainan Island of China were studied based on the geologic and geomorphologic observations. Most of the sandy beaches in the bay were wave-dominated and characterized by relatively straight and wide beaches on the seaward side of pre-modern sand barriers and medium sands on the beach faces. Observational analysis also demonstrates that beaches in Yueliang Bay were mainly intermediate beaches. The analysis of the beach type and stability provides certain instruction on the construction of the THNNR.

Semarang topography tends to flat withsome area as height as the sea level and even in some places below him. Various environmental problems faced by Semarang related to coastal and ocean dynamics are tidal inundation, land subsidence, and floods in the rainy season. This study was conducted to model the locations that vulnerable to inundated due to sea level rise. The calculation of sea level rise according to IPCC prediction. The data processing using Geographis Information System (GIS). Detailed Digital Elevation Models are very important to describe the distribution of inundated area caused by sea level rise phenomena. The results show that, the coastal Semarang have a high level of vulnerability to inundation due to sea level rise. The indications of the extent of area are affected by tidal inundation from 3.9% to 5.9% in one hundred years. Tidal inundation increase in the intensity and spreading along with the increase of subsidence. The modeling and monitoring of the vulnerable area very useful in the coastal zone management in Semarang City.

Typhoon waves play a major role in engineering and environmental problems. The long-term goal is to investigate variability and trends of typhoon waves over past 60years. However, the parameters in numerical wave models must to be calibrated before applying to any interesting region. In this paper, the most important parameters were selected from the source term of the SWAN wave model, and subjected them to sensitivity analysis to determine which parameter is the most sensitive. In order to find the optimal value of the parameter for improved modeling results, the ARS method was adopted to find the optimal value of the parameter to which the SWAN wave model is the most sensitive by comparing modeling results with observed data at three buoy stations in the northeastern Taiwan Sea near the coast. The procedure adopting the optimal parameter value of Cds in wave simulations did improve the accuracy of the SWAN wave model in comparison to default runs based on field observations at three buoys.

Characteristics of rainfall in the Indonesian Archipelago are closely related to oceanic oscillations in the Pacific Ocean and Indian Ocean. In this study, the daily rainfall data of Global Summary Of The Day (GSOD) from the National Climatic Data Center (NCDC) were used with careful consideration of data availability. The daily rainfall data from August 1985 to January 2010 were analyzed at 10 observation points. The results showed that significant differences of rainfall characteristics exist and they are classified into three regions as follows: ①Sumatra: multi-annual rain seasons for five long are dominant. Sever dry one or two years appeared in between the multi-annual rain seasons (1990-1992, 1999). ②Java Sea coastal area: clear variation in the annual rain and dry seasons. ③East Indonesia: multi-annual rain seasons same as Sumatra with clear annual fluctuation of wet and dry seasons.

These rainfall characteristics are discussed with the correlation of oceanic climate change indicators (DMI: Indian Ocean Dipole Mode Index, MEI: Pacific Ocean oscillation, PDO (Pacific Decadal Oscillation). Daily precipitation has high correlation with these indices in particular with MEI or PDO. Dry year appears in El Nino phase (PDO warm phase) and rainy year is the opposite. Dateline El Nino (CP El Nino) that warm seawater stays at the position of the International Date Line, is prone to extreme weather such as heavy rain. In fact, a significant rainfall occurs during the transition of MEI and PDO. The changes in average global temperature (IPCC), NAO (North Pacific Ocean oscillation index) and the PDO have the long-term variations of about 30-40 years. Apparently temperature and these indices have clear changes in 1903, 1944, and 1977. PDO seems to be shifting to cool phase (La Nina dominant phase) after 2005 and rainfall in Indonesia is also on the increase.

The influences of global climate change due to greenhouse effects on the earth environment will require impact assessment, mitigation and adaptation strategies for the future our society. This study projects future ocean wave climate in comparison with present wave climate based on atmospheric general circulation model and global wave model. Future change of averaged wave height depends on latitude strongly. On the other hand, the extreme wave height in the future climate will be increased significantly in tropical cyclone areas.

Direct consequences of global warming are thermal expansion of sea water and melting of glaciers and ice caps. Both effects would lead to a rise of the mean sea level. According to the fourth assessment report (AR4) of the Intergovernmental Panel on Climate Change (IPCC), the global mean sea level rose at a rate of 1.8 mm per year for 1961-2003 and 3.1 mm per year for 1993-2003. The fourth assessment report also projects that the sea level could rise by 0.59 metre in the 21st century while some recent studies suggest that the amount could be even higher - at one to two metres.

Located at the coast of the South China Sea, Hong Kong has experienced a rise in the sea level. Previous studies show that the sea level at the Victoria Harbour has risen significantly by about 2.6 mm per year since the 1950's. However, some other factors such as ocean currents, water discharge, subsidence and sedimentation are also influencing sea level at the regional scale. As the eastern side of Hong Kong is open to the Taiwan Strait and Luzon Strait, while the western side is at the Pearl River Estuary and the southern end is open to the South China Sea, the change in sea levels in Hong Kong and the adjacent waters would have regional variations. This study aims at determining the long term trends of the regional sea level changes in Hong Kong and the adjacent waters by examining the sea level data recorded since the 1950s by tide gauges at various coastal locations in Hong Kong and Macau. The satellite altimetry data are also used to corroborate the sea level change in the South China Sea with those in the Hong Kong Waters.

A Global Stochastic Tropical cyclone Model (GSTM) using Principle Component Analysis and Monte Carlo Simulation technique has been developed for assessment. Future change trends of tropical cyclone have been estimated from ensemble predictions of 8 different General Circulation Models and they were implemented in the GSTM. Consequently, future changes of tropical cyclone frequency and their intensity have been projected statistically and the effects of uncertainty of future change are also estimated.

It has been discussed that intensity of typhoon may increase in the future due to climate change. It is important to estimate the probable maximum magnitude of storm surges under the future climate for coastal disaster mitigation. In the present study, sensitivity of storm surge projection due to storm track in Tokyo Bay is discussed by employing the hundreds of different severe meteorological conditions generated by the potential vorticity inversion method. Ensemble numerical results show the most hazardous tropical cyclone track is different from most intense tropical cyclone track in Tokyo Bay. Estimated maximum storm surge in the Tokyo Bay is found to be 1.4 m which is the same level as the historical highest record.

Recent studies have identified the Philippines as one of the Asian countries subject to the major effects of climate change. Provinces situated along the Philippine coasts are considered the most vulnerable to the immediate consequences of sea level rise. Researches have confirmed the varying trends in sea level in the South China Sea, which is one of the largest semi-enclosed marginal seas in the northwest Pacific Ocean. An integrated vulnerability assessment is required to determine the degree of risks and the extent of the potential effects of sea level rise in order to formulate effective and efficient policies/measures related to climate change adaptation. Bolinao, Pangasinan is a province located in northwestern Luzon and bounded on the west by the South China Sea. In this study, three coastal communities in Bolinao, Pangasinan, namely, barangays Luciente 1.0, Germinal and Concordia were assessed for their natural and socioeconomic vulnerability to sea level rise. The socioeconomic data from each barangay were obtained through a qualitative survey. The Socioeconomic Vulnerability Index (SVI) was computed based on population, age, gender, literacy, employment, source of income and household size. Additional parameters include the family's capacity to recover from damage caused by flooding and typhoons and the community's awareness to the changing coastal environment. The Coastal Vulnerability Index (CVI) is calculated using parameters that describe the natural conditions, which include sea level anomalies, coastal topography, tidal range, recorded significant wave heights and coastal geomorphology. Sea level anomalies recorded by satellite altimeters validate the trends in mean sea level for the past decade. Coastal topography was assessed using a digital elevation model (DEM) extracted from high resolution satellite images and elevation values obtained using a terrestrial laser scanner. The tidal range was obtained from existing tide gauge records. All the included parameters for the SVI and CVI are weighted, classified and combined in ArcGIS for the determination of the Total Vulnerability Index (TVI). The integrated vulnerability for the three barangays is characterized in five classes, from very low to very high vulnerability.

The problem of climate change has become a hot issue around the world, and many countries are raise concern about this critical change. The United Nations International Strategy for Disaster Reduction (2007) reported that extreme climate will induced the increase the vulnerability of disaster, such as sea levels rise. This paper is aim to develop the neural network to evaluate the long term sea-level data and estimate the possible sea level in 2020 based on the observed tidal gauge data at Fukang Harbor, Taiwan. Comparing with other methods, it can be found that the neural network can be efficiently forecasted the long term sea-level using five years data and the sea level in 2020 has rise.

Preparing of adaptation strategy against global warming is one of the important issues. The purpose of paper is to show the typical effect of adaptation and early adaptation for reducing vulnerability in developed country and developing countries. The quantitative results of vulnerability assessments following trial scenarios of adaptations show that effect of early adaptation is strong in developing courtiers in case of good economy growth.

Sea dikes and estuary dikes of Vietnam have been constructed in a long time with different quality. Most of them had constructed on the natural lines in which the foundation is very complicated. When a land is increased, a new line of dike will be relocated, that a new dike will be laid on the soft soils. The safety and economic of new dike as well as short time of construction are dependent on construction method. The construction method for sea dike on soft soils with high seepage, low strength and settlement will be presented and discussed in this paper. In Vietnam, construction methods used for soft foundation will be sand- sub base, strengthening of foundation, control settlement referring to consolidation [4].

21^st century is the century of sea, this should also include the water resources development. Australia is the driest country in the world, its southeast Queensland is experiencing extreme water scarcity. Intensive research has been conducted and many solutions have been proposed in order to secure its water deficit that is 500GL/year in 2050, such as more inland reservoirs, wastewater recycle and reuse, and desalination plants etc. By analyzing the rainfall data (1200mm/year) and runoff data (10,000GL/year), it is found that the assumption in the existing proposals is not true, in this region the shortage is not water, rather a lack of storage capacity. Based on this discovery, the application of coastal reservoirs in this region has been discussed and analyzed in terms of water supply reliability and water quality. An innovative design of coastal reservoir is proposed to prevent the external pollution by seawater and land-based contaminants. The new solution has been compared with the previous proposals based on their sustainability, impacts on environment and ecosystem, construction and operation cost, and green-house gas emission. It is found that the strategy of coastal reservoirs meets the regional water demand well, and it is sustainable, environment-friendly and cost effective. Most importantly, the example shown in this paper shows that the proposed strategy may eliminate the need of desalination in other similar areas of Australia as well as the world.

The quarter-circular caisson breakwater (QCB) is a new-type breakwater, and it can be applied in deepwater. The stability of QCB under wave force action can be enhanced, and the rubble mound engineering can be less than that of semicircular breakwaters in deepwater.

In order to study the wave force distribution acting on the QCB, to find wave force formula for this type breakwater, firstly in this paper, the distribution characteristics of the horizontal force, the downward vertical force and the uplift force on the breakwater have been gotten based on physical model wave flume experiments and on the analysis of the wave pressure experimental data. Based on a series of physical model tests acting by irregular waves, a kind of calculation method, which was modified from Goda Formula, was proposed to carry out the wave force on the QCB.

Secondly, the reliability method with correlated variables was adopted to analyze the QCB, considering the high correlation between wave forces or moments. Based on the observed wave data at engineering region, the reliability index and failure probability of QCB were obtained as well as the proposed partial coefficients of wave loadings. Finally, the design expressions of QCB for anti-sliding and anti-overturning were presented.

Analyses of the directional wave spectrum in shallow water area using video images data are presented. The technique is based on time series of the pixel brightness on video images. The study was examined using video images data at Hasaki beach in Japan. Determination of directional wave spectrum is examined using two different configurations of arrays. The result indicated that in shallow water wave directional spectrum derived from video images was the narrowest at peak frequency and direction.

Breakwater is a very important anti-wave structure in harbor and near shore engineering. The stability of superstructure, armor unit, toe and apron is the major consideration during design. For the calculation on size of armor unit, Hudson's Formula is adopted in many countries' design standard. This formula is developed by extensive hydraulic model tests. But, due to the limitation of test condition, this formula can't reflect the nature situation completely. In actual design progress, the verification of armor unit size is always combining with 3D and 2D stability wave physical model. However, due to the test methodology difference between 3D and 2D model, the scope of application is also different: 2D physical model is suitable for trunk part of breakwater with normal incidence wave, 3D model is more suitable for complex wave condition. In this paper, based on some project of Malaya, from the comparison between original design and model test result, we can know that: the wave condition is very complex in head part of breakwater, 3D model result is more feasible for stability verification; For trunk part of breakwater, the test result of 2D model is quite similar with calculation result of Hudson's formula. But for slant incident wave, the wave forces are lower than those from direct orthogonal waves, the test wave conditions should be hence reduced with relevant angle.

The efficient management of seawall is essential to maintain a safe community in the coastal areas, and one practical way is to set up a reliable fundamental seawall information system to support seawall management decision. In this paper, the general management situation of seawall constructions along China coastal areas is introduced, and then a Decision Support System for Seawall Safety Management (DSS-SSM) based on Geographic Information System (GIS) and database technology is initially proposed and designed. The basic framework of DSS-SSM consists of three parts which are fundamental information database, model base and evaluation management system. Since all the models are incorporated together, disaster prevention and reduction departments can simulate various scenarios with different considerations, then evaluate seawall security situation and make decisions of coast protection more effectively.

A local remote sensing system was developed to monitor the morphological processes on sandy beaches. The monitoring station consists of a network camera and a host computer mounted on a high vantage point. The data acquisition procedure is fully automated so that photographic images can be recorded continuously in a cost-efficient way. The system has been applied to the field observation of Hachigasaki beach, Ishikawa, Japan. Continuous measurements have been conducted since November 2007 over an alongshore stretch of approximately 2 km. The accuracy of shoreline detection based on image processing has been confirmed through comparison with an in-situ survey using a total station. Quantitatively good agreements are obtained. Various morphological features have been captured such as the splitting of a sand bar as well as the formation of beach cusps. These results show the high capability of the developed system to remotely measure the coastal morphology on sandy beaches.

Experience from construction of a self-adjusted rubble-mound breakwater at Grassy, King Island, in Bass Strait, where severe wave conditions was up to 7.6 meter incident waves, together with careful observation on large scale model tests (1:10 geometric Froude similitude without distortion) resulted in conclusion that stability of rubble mounds depend on mass stability of the mounds. Although the function of individual armor rocks is still important to cover the core layer in order to achieve static stability, use of equilibrium beach profile principles in predicting final profiles will result in more effective use of overall available material and smaller armor rocks. This study combines observation on the prototype, development of equilibrium beach profile theories, progress in reshaped berm-breakwater design, and large scale model tests to define a new procedure for rubble-mound breakwater/revetment trunk design and to predict the future of Grassy breakwater.

Fishing harbours in India are mostly located in the tidal inlets, which provide natural shelter to the fishing boats. However, siltation near the mouths of tidal inlets and rivers is a perennial problem in the Gangetic Delta in Eastern India. Maintenance dredging involves huge expenditure. Shankarpur, situated along the coast of West Bengal is a traditional fishing area for more than four decades, where mechanized fishing vessels pass through the tidal inlet (locally known as Dubda Canal) for reaching the fishing harbor located inside the channel. Due to gradual accretion, sand spit had been formed at the inlet mouth thereby degrading navigability. Another critical problem was severe erosion on the western side of the channel mouth. Mathematical model studies were carried out to arrive at the suitable option for training works along with dredging of channel. A 425 m long groyne was suggested for the dual purpose of avoiding siltation in the mouth of the channel and to protect the eroding beach at Digha near the inlet. The suggested groyne is low crested and was economized by making it sloping, submerged and using stone-filled gabions in the armour. Later, the crest of the groyne was elevated and it was renovated by placing tetrapods in the armour layer. The design and the performance of the groyne, which highlights the model-prototype conformity has been discussed in the paper.

In this study the static load carrying capacity of a new wave dissipating concrete block is estimated by performing numerical analysis and static load test. The fiber reinforced plastic bar is used to supplement the capacity of the concrete block. The amount and the location of the reinforcement are decided by referencing the numerical analysis results. The load test is conducted by applying static load at the top of the concrete block. The fracture occurs at the load level of 350kN which is about 6.2 times of the weight of the block. Also, the test blocks show strength capacity of over 900kN.

Wave overtopping is one of the most important design parameters which effects on the harbor calmness, operation and structural stability. Therefore the reliable estimation of wave overtopping is indispensible for designing the coastal structures. Recently, it is known that EurOtop (2007) is the most widely and newest design manual for the estimation of wave overtopping. In this study, the wave overtopping for vertical structures are measured and the empirical formula will be suggested concerning the wave period effect as well as the wave spectrum. The effect of wave periods will be analyzed using the relative water depth, kh.

Safety of sea dike structures is related to several important factors, which usually have some uncertainties in engineering practice, sea dike structure safety by reliability analysis is initially studied in this paper. Firstly, the main influencing factors and the basic methods for the analysis of sea dike structure safety are reviewed, and then the basic framework of reliability analysis system is constructed. Secondly, several sea dike structures failure modes, such as excessive wave overtopping, failure of armor block, local scour of the sea dike toe, seepage, parapet wall failure and overall structure failure are analyzed and the corresponding performance functions are proposed. Finally, the reliabilities of those methods are applied to several engineering case studies.

It's been reported that the global warming effect has invoked the ever increasing typhoon intensity and long-term sea level rise which jointly cause severe wave overtopping of breakwaters or shore dykes. In this paper, Deformable Rubber Membrane Parapets(DRMP) which not only suppress the wave overtopping in storm periods but also can retain coastal seascapes in normal days are presented. With numerical analyses using a nonlinear finite element program and hydraulic experiments, the air controlled expansion and contraction of the parapets are investigated together with their structural behaviors and stability against wave overtopping.

In 2007 an earthquake occurred along the Sunda Megathrust, caused by a partial rupture of the thrust along the Mentawai patch. Experts suggest that the stress released by this earthquake was only a fraction of the accumulated stress, thus another major earthquake is to be expected in the north-western segment of the patch in the near future. The area is facing the coast of West Sumatra Province, as well as the cities of Padang and Pariaman. In 2009, this area was affected by a 7.6 earthquake whose epicenter was located on the subducting Australian plate. Although this earthquake did not contribute in releasing the tension on the Mentawai patch, it showed the area's vulnerability to earthquakes, resulting in more than 2650 buildings damaged and more than a thousand of fatalities. The city of Pariaman was the closest to the epicenter, and suffered the loss of 37 lives as well as severe damage to its buildings and infrastructures. Whilst planning for such events have always been of great importance in West Sumatra, providing short-term feasible solutions is now extremely urgent. The work described in this paper is part of a research project looking at developing risk management strategies for the cities of Padang and Pariaman, West Sumatra. In particular, this paper focuses on the study carried out to assess evacuation scenarios. The analyzed scenarios depend on variables including: time of the day in which the event occurs; means of transportation; and possible behaviors of the evacuees. It is impractical, or rather impossible, to forecast such variables. Hence it is required to explore different scenarios to produce a comprehensive assessment, to enable the development of flexible solutions for a robust management of the risk. This study was carried out including consultations with local authorities and emergency planners. The consultations provided an understanding of local risk perception and possible responses for building the models; enabled targeting the study to meet actual need; and contributed in developing solutions that could be actually implemented within the current policy framework. The models were developed by using different methods, including network analysis and agent-based techniques. The integration of the consultation with forefront modeling techniques contributed toward the development of feasible and scientifically-based solutions for managing the risk.

The land use for building which keeps increasing in urban areas cause problems in the future, particularly related to the availability and capacity of land in urban areas, in fulfilling the need for development and sustainable urban development. The purpose of this research is to investigate the relationship between area of land use for building and time in the future, until when the land is capable of supporting the growth in the use for building, and how to deal with land use for building so that the land in the territory of Palu as a coastal city is capable of supporting the growth in the longer use. The research method used is the approach of quantitative method by using several analytical techniques, among others: land capacity analysis, regression analysis, projection analysis, and overlay analysis, and by using the help of some programs and software to assist the analysis. The research data consists of spatial data including data on the number of land users of protected areas and cultivation areas obtained from the Revised Map of Spatial Planning of Palu City in 2010, and aspatial data including data on the number and population growth, the number and growth of the building in form of a time series of data obtained through document registration and GIS techniques. The results showed that the land use for building in Palu city on the future having growth average 2.50% per year; cultivation area will be full of buildings in the year 2212. In order to get the land in the territory of Palu as a coastal city is capable of supporting the growth of the land use for building much longer, some efforts are needed to be done through reducing the growth and the extensive land use for building per one user, controlling the population growth, adding the width of area, and planning storey buildings in certain zones.

This study newly develops a system for extraction of coastal shoreline and near-shore bathymetry based on the ALOS PALSAR image. Capturing the back-scattering of the radiated micro waves at the surface of the earth, PALSAR has strong advantage in that the surface information is not interrupted by optical obstacles such as clouds. Comparisons of the image and measured shoreline data revealed that the shoreline can be detected where abrupt change of the horizontal distributions of backscattering is observed. The present system also estimates near-shore bathymetry based on the spatial distribution of wave crest lines observed in the image. The image is first filtered to remove noises and the local wave length is determined as a shifted distance that yields the peak correlation coefficient. The proposed system is applied to the north-west coast of Sri Lanka and, through comparisons with measured data, applicability of the system is investigated.

The basic principle involved in the design of berm breakwater is provision of a wide berm at or around the water level with smaller size stones in the armour, which are allowed to move till an equilibrium slope is achieved. This paper presents the results of experimental studies conducted on the wave run-up, run-down characteristics of berm breakwater using concrete cube as artificial armour unit. The experiments were conducted under following conditions, berm width = 0.45m, water depths 0.37, 0.40 & 0.43m, breakwater slope 1:1.5. The weight of concrete cube is 79.5 gm. The wave heights used in the experiments are 0.10, 0.12, 0.14, and 0.16 m and wave periods are 1.6 and 2.0 sec. From the experimental study it is found that the run-up is more for longer period waves in comparison with the shorter period waves. With the increase in deep water wave steepness the run-up and run-down was found to decrease for all the water depths considered. The run-up values (Ru/Ho) vary from 0.52 to 1.08. The range of run-down values (Rd/Ho) varies from 0.45 to 0.88. In berm breakwater the run-up and run-down values were reduced by 35.91% and 23.81% when compared with conventional rubble mound breakwater.

The potential impacts of climate change on existing coastal hazards are likely to increase. During this century our coastline is likely to be impacted by climate change. Impacts such as sea level rise and an increase in frequency and severity of storm events are likely to lead to a greater coastal inundation and erosion. Hard approach protection has been used despite the expensive cost and less environmentally friendly. It is necessary to develop an eco-protection concept using vegetation or combination of vegetation with civil structures. Combined model is likely to be cheaper and is environmentally sounder. This paper presents the results of experimental research on the performance of mangroves as shore protection (Thaha, 2003) combined with a low crested rubble mount breakwater by Seabrook & Hall (1998) in Pilarczyk KW et al. (2003). The results showed a maximum wave transmission can be reduce 48% up to 85% for tidal ranges of 2.00 m for a 50 m width of composite structures with mangrove relative roots density in the range of 0.009 to 0.073. The increase of transmitted wave height throught the LB-BW (without mangroves) due to the sea level rise can be reduced by combining it with mangrove forests where the mangrove wave damping capacity will increase by the growing of mangrove roots density. The combined equation of wave transmission coefficients consisting of both mangrove roots and low crest breakwater parameter is presented at the end of this paper.

The HZM (Hongkong-Zhuhai-Macao) bridge connects Hongkong, Zhuhai and Macao district, and it stretches across the Lingding sea in the Pearl River estuary. A lot of piers and three large artificial islands in the sea will have some influences on the hydrodynamic environment of the Pear River estuary. In this paper, a 2D tidal current numerical model is introduced to simulate the hydrodynamic impact from the HZM bridge. For the broad water area of the Lingding Sea, the water area covered by the model should be large as for as possible. And the lower limit of the pier is 2.0m. Thus the unstructured grids are selected to split the computed area. The grids could be enlarged far away from the HZM bridge, and the grids would be small in the bridge area. And the FVM(finite volume method) is adopted to solve the tidal current governing equation, for it can satisfy the control equation's conservation and has a high calculated precision. The simulated results show that the Hydrodynamic influence is concentrated on the 5.0 km range from downstream to upstream nearby the navigation zone and the 1.0 km range of bridge site in not-navigation zone, and the tidal range reduction is limited 0.03m and the tidal prism reduction is not more than 1% in the Lingding Sea after the HZM bridge is constructed. Therefore, the HZM bridge has little influence on the distribution of hydrodynamic environment in the Pearl River estuary.

A schematized process-based model of tidal flat evolution was constructed with dimensions similar to the tidal flats near the Wanggang Mouth at the central coast of Jiangsu, China. The simulated flow patterns agree qualitatively with field observations from literature, i.e. involving tidal asymmetry, current directions and tidal wave features. The analysis of the sediment fluxes depicts that deposition occurs from spring tide to neap tide and erosion from neap tide to spring tide. A sensitivity analysis test of the morphological acceleration factor shows that the ideal value is only 1, implying no acceleration factor. The long-term mudflat evolution has been simulated starting from an initial sand seabed. The simulated morphological characteristics, including the convex cross-shore profiles with steeper slope and the southern prograding coastline with slight higher accretion rate compared with the north side, are qualitatively consistent with reality. Most importantly, the creek patterns are roughly reproduced.

The reason for the occurrence of downtime problems in Pohang New harbor was analyzed by using the extensive field measurement data of short and long period waves and winds for more than one year, the precipitation data provided by KMA(Korea Meteorological Agency), and the downtime records during the measurement period. It was found that downtimes occur because of the short period wave of which height is higher than loading criteria and the swell with even smaller wave height but longer period(more than 10 sec) and fig-waves of which height is higher than loading criteria. Long period components(more than 5 min.) is seems to be related with the downtime problems. This study shows what was able to improve harbor calmness if short period waves and swells were blocked effectively.

Long-term variations in the riverbed of the Tedori River, Japan, were investigated using a set of field surveys conducted over 30 years. The results revealed that the sediment volume of the entire study reach declined by 11.5 × 10⁶m³ from 1950 to 1979. Correspondingly, the riverbed has undergone serious and rapid erosion, lowering by 0.5 to 3.5 m as a result of erosion at a rate of 0.06-0.10 m/year. The temporal and spatial variation of the sediment volume and corresponding riverbed response were related to anthropogenic activities such as material mining and dam construction. These variations were effectively captured using empirical orthogonal function (EOF) analysis. A collation of EOF results between the river and the coast was conducted to fully realize the cumulative anthropogenic impacts on the river-coastal watershed.

The tidal sluice was planned to build in the Mulan Creek estuary, but siltation in the rivers downstream sluices is universe in China, usually making the discharge capacity of rivers decrease obviously and threatening the flood control in the upper reaches. In order to study the influence on flood control when building tidal sluice in the Mulan Creek estuary, a physical model was constructed in NHRI, with the horizontal scale of 1/335 and vertical scale of 1/65 respectively. Hydrodynamic environmental change and sediment movement after building tidal sluice were studied, in order to predict the sedimentation rate and the influence on flood control after building tidal sluice.

Following a brief introduction to the tidal bore on the Qiantang River, the research history of the tidal bore is reviewed in this paper. Then, the research advances of the tidal bore after the founding of the People's Republic of China are demonstrated in detail according to the research methods, including field observation and analysis, theoretical analysis, numerical model and physical model. Finally, research prospects of the tidal bore are proposed. In the latest 50 years, the research methods of the tidal bore have been developed considerably by adding “mathematical model” and “physical model” to “observation and analysis of field data” and “theoretical research”, broadening research methods and enriching research connotation. In the recent three decades, the bore research has entered a new era of conducting study, application and enhancement at the same time.

The South Channel of the Changjiang River ranges from the lower part of the South Branch to the South and North Passage bifurcation, its evolution has important impacts on its upper and lower reach. In this paper, based on underwater topography data of the South Channel in many typical years from 1842 to 2004, the historical evolutions of the South Channel are studied. The results show that, (1) the South Channel has undergone 3 evolutional stages, before 1950s, water and sediment could exchange freely between the South and North Channel, during 1950s˜1960s, the South and North Channel completely separated, and after 1970s compound channel with separated flood and ebb tide river courses formed gradually; (2) the South Channel evolution is mainly impacted by natural power before 1950s, but human activity functions strengthened gradually after 1950s; (3) in recent years, evolutions of the South Channel mainly reflected in the development of the compound channel, but cross sections are basically stable as a whole.

In Mokpo coastal zone, physical factors generating ebb-dominant flow were reviewed by observed data and numerical modeling. Influence of critical depth for wetting and drying, bottom shear stress, coastal reclamation, tidal amplitude, and nonlinear tide at open boundaries on the change of ebb-dominant flow was investigated by applying a two-dimensional hydrodynamic model. The simulation results for a variety of conditions showed that critical depth for wetting and drying has little impact on the generation of asymmetric flow, but large bottom friction stresses generates ebb-dominant flow. Conversion of tidal flats into land swells ebb-dominant flow, but conversion of tidal flats into sea lessens ebb-dominant flow. Nonlinear tides at open boundaries play a decisive role in the generation of asymmetrical tidal flow.

In this paper, the topography and the characteristics of flow and sediment at the estuary are analyzed. By using the hydrology data measured at Datong Station, the long-term variations of flow and sand upstream Datong Station are also analyzed. The conclusions about the changes of flow, sand, salt intrusion and sandbank in the estuary are summarized according to the previous feasibility study for the Three-gorge Project (TGP). The data measured during TGP operation from 2003 to 2007 are also analyzed.

The comparison of the recent 40 years' terrain dataset showed the entrance of XiaoMiaoHong channel had an evolutionary tendency of deposition at north and erosion at south waterway. The north trough silted constantly to disappear while the south trough developed adequately. This article discussed the mechanism of the change in deposition and erosion at different channels these years from the viewpoint of hydrodynamic, according to analysis of field data and the tidal current Mathematical model we established. The result showed XiaoMiaoHong Tidal Inlet was mainly controlled by tidal. The reason, that XiaoMiaoHong channel exhibited a state of deposition at north and erosion at south recent years, has close connection with the tidal current characteristics at this area. The north channel, which exhibits deposition, is a channel that flood predominate, no matter according to its flood-ebb property or the direction of residual current. While the south channel, which exhibits erosion, is just the opposite.

Taking stopping flow in the South Branch of Oujiang Estuary as an example, tidal current and sediment problems related to stopping flow in one bifurcated branch of a complex tidal estuary are studied in this paper. A numerical model of tidal current and sediment movement under the combined action of wave and current are set up with irregular triangular grid. The model is verified with in situ data, and the results show that the calculated water elevations at 19 stations, currents, suspended sediment at 19 vertical lines and seabed evolution are all in good agreement with measured data. This numerical model is applied in the tidal current and sediment movement simulations in stopping flow transport through the South Branch of the Oujiang Estuary and the feasibility to cut off the flow in the South Branch of the Oujiang Estuary is demonstrated by numerical simulation experiments. The results show that flow cutoff in the South Branch by heightening the present submerged dyke is technically feasible as far as its impact on hydrodynamic sediment environment is concerned.

Siltation in the rivers downstream of floodgates is serious in China, making the discharge capacity of rivers decrease obviously and threatening the flood control in upper rivers. Tidal wave deformation is one conclusive dynamic factor leading to siltation downstream of floodgates in estuaries. The hydrodynamic characteristics of tidal wave deformation are different with different river length downstream of floodgates, so the fluvial processes and morphology characteristics are also different. A 2-D numerical model is established to simulate the tidal wave deformation with different-length river downstream the floodgate. The changes of tidal level, flow velocity and phase difference are simulated before and after the construction of floodgate. The length of river downstream of floodgates influences tidal wave deformation obviously, and several conclusions are obtained in this paper which can provide some theoretical basis for the prediction and analysis of the siltation characteristics in lower reach caused by floodgates with different length in estuaries.

An estuary is the wide part of a river where it joins the sea. It has an unique ecosystem and potential values for economics, whereas it is hard to control the water level and bed changes in an estuary due to a tidal movement. In this study, the flow characteristics of Han River Estuary located in Korea were investigated by using a two-dimensional numerical model according to the assumption of shift and modification of the Shingok submerged weir. The two-dimensional analysis has contributed to our understanding of the hydraulic effects induced by shift of the weir on the topography, especially wetlands. The tide and flow discharge of 2007 were adopted as an input data for the simulation. The tidal data contained both spring and neap tides, and the flow discharge condition was divided into monsoon and normal seasons. The boundaries of this study were Han River Bridge, Tongil Bridge, and Yu island. The numerical model which was used as a tool to simulate the flow field was calibrated and verified based on the measured data acquired from Jeonlyu station. The simulation results showed that influence area of seawater changed depending on the weir shift, and the water level at particular station fluctuated according to the condition of tide and flow discharge. Especially the low-tide level increases seriously due to the weir shift at Janghang wetland located in Han River Estuary. Thus it is expected that the wetlands where an area of land consisting of soil saturated with moisture are transformed into completely submerged land. Also the tidal effects fall back to the downstream by means of weir shift.

A process-based 3D hydrodynamic model was developed to study the changes in hydrodynamic circulation in Jiangsu coastal areas due to a large scale tidal flat reclamation planning project. The engineering sedimentation method was used to calculate the possible sediment siltation intensity in the vicinal sea area of reclamation project. It found that: the location of tide-free point of M2 tidal constituents moved about 3km from the present place to northeastward. The propagation velocity of tidal wave from Sheyang estuary to Jianggang is accelerated and tidal range is enlarged. After the completion of the first and second stage's reclamations, the peak velocity and unit tidal discharge in Xiyang tidal inlet increased about 20% and 5%˜10%, respectively. But there were little changes in other tidal inlets due to beach reclamation near these tidal inlets. After the completion of the third stage's reclamation, both the peak velocity and unit tidal discharge in Xiyang tidal inlet further increased over 20%, however, decreased in Xiaomiaohong tidal inlet about 20% and 10%, respectively due to drastic reduction in tidal inlet width. The annual siltation intensity was about 30˜50 cm/a near the tidal flat reclamation project.

Several field measurements were conducted to study the characteristics of tidal circulation in the Han River estuary (HRE) on the western coast of Korea. The HRE is macro-tidal coastal zone with a mean depth less than 10 m and a tidal range varying 3.5 (neap) to 8.0 m (spring). The tidal amplitude to depth ratio is large enough to generate non-linearity in the tidal wave. The harmonic analysis results at HRE indicate that relative phases of (2M₂ – M₄) are less than 180° for most of measured points. Hence, the analysis of relative phases is shown that HRE type is flood dominant. But this method is typically based on the non-linear distortion of the tidal current in tidal lagoon system where freshwater discharge is assumed to be relatively small. We investigated the tidal current from 3 periods (December, 2005, September, 2007 and May, 2010) at the nearby station over a 15 days or 35 days. The statistical methods of ebb and flood used to characterize the tidal circulation were as follows: the duration of ebb and flood currents; the time to slack water of ebb and flood current; and the magnitude of the mean and maximum ebb flood currents. Both the maximum and mean current velocities during ebb exceed the corresponding velocities during flood. The averaged duration-difference during 3 observation period was ebb dominant. The duration percent of ebb is larger than that of flood. HRE has ebb dominance that is stronger and longer than flood. Such asymmetry can be explained in terms of the hydraulic current generated by the continuously changing tidal ranges and phases at different points (e.g. T0 and T8).

The latest version of the third generation spectral wave model, WAMC4, is adopted for the long-term hindcasting of wave climate for the Jiangsu coast. The model is driven by the NCEP/NCAR reanalysis wind data spanning the period of 1951-2010. A 3-level nested downscaling framework, covering the oceanic domain (Northwest Pacific Ocean), the regional domain (East China Sea) and the local domain (Jiangsu Coast), is established to simulate both wind and swell waves. Based on the long-term modeling results, the distributions of mean and extreme wave heights are obtained. Those results are valuable for the coastal engineering such as the large scale tidal flat reclamation project along the Jiangsu coast.

Drifter garbage is transported by surface current. Surface current consists of tidal component and wind driven current. So we analyzed the data of surface current observed High Frequency Radar and ocean surface wind by means of multi-regression analysis in Tokyo Bay. The results of the analysis show that the horizontal distribution of wind driven current is influenced by bay topography. The wind effect estimated by numerical simulation is smaller that effect estimated by HFR data.

The numerical models containing estuarine and coastal numerical model (MIKE21) and wave propagation model (SWAN40.71) are used. Basing on the applicability of the validation, the storm tide and typhoon waves in front of the seawall along north bank of Qiantang Estuary in Zhejiang Province are simulated, which is caused by No.5612 typhoon that is most powerful typhoon landing China, and is selected as a typical super typhoon in this paper. Overtopping rate and its action on seawall are simulated in wave sluice. Simulation results show that: 1) Super typhoon lands at average annual hightest tidal level along north route, overtopping rate of north bank can reach 0.4˜1.4 m³/(m.s), and the outburst of seawall will occur. Landing at high tidal level of mean astronomical tide, overtopping rate of seawall from Gp to Zp can reach 0.17˜0.5 m³/(m.s), the seawall will be seriously damaged, and then will bursts. Landing at high tidal level of small astronomical tide, overtopping rate can reach 0.19 m³/(m.s) in some site from Gp to Zp, local damage of seawall will appear. 2)super typhoon lands in local average annual highest tidal level along middle-north route, it will cause overtopping rate of 0.11˜0.46 m³/(m.s), seawall burst, but landing in high tidal level of mean astronomical tide, overtopping rate will drop to be 0.0˜0.078m³/(m.s), the inner slope of seawall remains stable basically. The results have practical significance for design of coastal engineering and minimization of damage during super typhoons.

A proposal to construct a deep water port at the Sagar Island in the Hooghly estuary, India is in the pipeline. Detailed surveys and investigations have been carried out as a part of the preparation of feasibility report for port planning. In this paper, morphological changes of the Hooghly estuary such as aggradations and degradation of the shoals, sand bars, and islands in the estuary which will have a bearing on the possible selection of the port location have been thoroughly studied. The morphological changes that have taken place over the years have been related to various estuarine forces. The studies have been aimed to the selection of the new port location.

To calculate the total mass flux that change in time and space in the Yeomha Channel of Gyeonggi Bay, the 13 hour bottom tracking observation was performed from the entrance (Line1) of the Yeomha Channel and the southern extremity (Line2) during the spring and neap tidal cycles. The value of the total mass flux (Lagrange flux) was calculated as the sum of the Eulerian flux value and stroke drift value and the tidal residual flow was harmonically analyzed through the least-squares method. Moreover, the average during the tidal cycle is essential to calculate the mass flux and the tidal residual flow and there is the need to equate the lattice of repeatedly observed data. Nevertheless, due to the great differences in the studied region, the number of vertical lattice tends to change according to time and since the horizontal lattice differs according to the transport speed of the ship as a characteristic of the bottom tracking observation, differences occur in the horizontal and vertical lattice for each hour. Hence, the present study has vertically and horizontally normalized (sigma coordinate) to equate the lattice per each hour. When compared to the z-level coordinate system, the Sigma coordinate system was evaluated to have no irrationalities in data analysis with 3˜5% of error. As a result of the analysis, the tidal residual flow displayed the flow pattern of sagging in the both ends in the main waterway direction of Line2. In Line1, it was confirmed that the tidal residual flow was dominated by favorable pressure caused by the differences in height of the sea surface. As a result of the total mass flux, the ebb properties of 576cms and 67cms were observed during spring and neap tides, respectively. This is the intertidal region between Youngjong-do and Ganghwa-do and estimated to outpour approximately 935cms during the spring tides and approximately 315cms during the neap tides.

The seiche motion due to long waves at Young-il man new harbor in Korea have occurred frequently which produced undesirable wave and ship oscillation in the harbor, especially during the season with waves coming from the east-northeast direction. This paper presents results of a computer simulation study for exploring seiche reduction measure at Yeong-il man new harbor. Several resonant modes are clearly seen from simulation results that resonant periods are 35s˜45s and 6min˜14min. This study make set up a target resonant periods for seiche reduction measure which is 35s˜45s. These periods have a bad effect on small sized ship motion at Young-il man new harbor. It is seen that the seiche reduction measure is effective when the quay wall replace to the energy dissipating structure.

It has been 10 years since the wetlands restoration project that implemented in 2002 in Yellow River Delta, China. The project mainly aims to improve the natural habitat for rare birds through hydrological process's modification. A water volume-water level control technique was demonstrated and applied to prevent salinization by diverting freshwater into wetlands. In this study, we present the restoration effects and assess the rationality through bird-habitat responses based on monitoring data from 2001 to 2010. Results show that the restoration has achieved some positive effects, but lacks adjustment to unexpected situations. We propose that an establishment of water level-volume model and the calculation of appropriate ecological water requirement threshold are effective for wetland restoration and protection.

The velocity of seawater flow has a strong influence on the power output of tidal current generation systems. Therefore, CFD (Computational Fluid Dynamics) analyses are performed to investigate the effect of shroud geometry variation on the flow characteristics for nozzle-diffuser and cylinder-diffuser type shrouds used for controlling seawater flow in horizontal axis tidal current turbine systems. Through these analyses, fluid velocity distributions and maximum velocity locations inside the shrouds are compared. Predicted results show that the flow fields and the peak velocity depend on the shroud angle. Especially fluid velocity in the cylinder-diffuser type is rather high in overall cylinder part while high velocity zone in nozzle-diffuser type locally appears near the minimum sectional area. It can also be seen that fluid velocity at the centerline of cylinder-diffuser type shrouds increases near the entrance, and reaches a peak, and then decreases rapidly near the outlet before converging. Velocity variation with the shroud angle is much higher in cylinder-diffuser type, and maximum peak velocity is obtained for θ₂ =0.315 rad. These results can be applied to the optimal design of shroud in a tidal current power generation system for the development of the efficient systems.

Observations of longitudinal-channel fluid mud dynamics is conducted in the context of a cold-air wave on October of 2010 at the Yangtze Estuary, China. The measurement data reveals that just after the wind wave event, a large number of cohesive fine sediment particular materials are trapped as a status of fluid mud along the dredged navigation channel in the North Passage. The mechanism and transportation of the wave-forced fluid mud may be relate to both wave agitation and the spring-neap tidal variations. At the same time, some process-oriented sedimentary processes, such as, flocculation, stratification and trapping effects (sediment and salinity density flow), and the overall of flow regimes, tidal asymmetry (Shi, 2010) also may have some relationships with the formation and dynamics of fluid mud, but it need more evidences to discourse the occurrence of fluid mud in the river- and tidal- dominated estuary.

With the rapid socioeconomic development and urbanization, reclamation of mudflat resources has become an important way to ease the contradiction between land supply and demand. Irrational exploitation of limited mudflat resources has seriously affected natural evolution of many estuarine and coastal areas, weakened the regeneration of these resources, and threatened flood control, water security, and consequently the sustainable socioeconomic development in estuarine and coastal areas. Mudflat resources and their capacity are limited by the level of science and technology, in a certain period of time. Therefore, the ecological environmental health should be protected to ensure the sustainable development. This paper presents a review on the state-of-the-art knowledge concerning mudflats development and management, including development and utilization of mudflats and their impacts on environment, assessment of sustainable development, as well as construction of management system. Some necessary research fields and topics in the future are also recommended.

The Hongqili waterway, one of the main navigation channel in the Pearl River estuarial network, locates in the southeastern part of the Pearl River Delta, where is right adjacent to the Lingding Ocean. Thus this waterway is under the strong influence of both runoff and tides, resulting in sophisticated hydrological environments and erosion & sedimentation variation. A harbor project named Dagang is going to be carried out in the Hongqili waterway in order to enhance the local transportation performance. More than twenty docks of 1000-t class (can be upgraded to 3000-t class) will be constructed according to the design so that large amounts of excavation and dredging will be required in the harbor district and its navigation channels. This paper calculated the future siltation amounts in the excavation and dredging areas after the accomplishment of Dagang harbor. A two-dimensional numerical model was established to achieve this purpose. In this model integrated datasets including hydraulic, tidal and sediment data were all put into consideration. The model verification was based on the data series of both flood seasons (July ˜August in 2004) and non-flood seasons (April in 2008, January in 2009).

By theory analysis and physical model test, the disciplinarian on wave crest height has been studied when waves act the single and group pile-gravity type complex structures. Get the relationships between the wave crest and wave height, wave length, wave period, dimension of pile-gravity type complex structure and wave incidence angle and put forward the calculation method on wave crest height of pile-gravity type complex structure. The method can be adopted to design the practical project for wharf surface elevation of pile-gravity type complex structure.

In this work the issue of wave-induced flow structures that develop around a large-diameter surface-piercing vertical circular cylinder is addressed. A strictly-linear wave case is considered and simulated numerically, solving the Euler equations in primitive variables, and the results are compared with those obtained from the corresponding close-form velocity-potential solution. Then, the swirling-strength criterion for flow-structure eduction is applied to the primitive-variable Euler-equations-derived velocity field. It is found that differently-shaped flow structures develop at the free surface and under the free surface, in particular at the cylinder wall. This field of structures is not detectable from the potential-derived velocity field, due to the purely mathematical nature of the latter.

This study examines the reflection and transmission coefficients of a submerged slightly inclined porous plate with a partially reflecting sidewall. The multi-domain boundary element method (BEM) is used to obtain the solution. The effects of several main factors, including the plate inclined angle, the reflection coefficient of sidewall and the relative space between the plate and the sidewall, on the reflection and transmission coefficients of the porous plate breakwater are examined. Some significant results are presented to practical engineering.

The evaluation of wave-induced pore pressures and effective stresses in a porous seabed near breakwater heads is important for coastal engineers involved in the design of coastal structures. Most previous studies have been limited to two-dimensional (2D) or three-dimensional (3D) cases in front of a breakwater. In this paper, a three-dimensional numerical model for the wave-induced seabed response around breakwater heads is developed. The 3-D wave model was based on the Navier-Stoke equation with wave generation model. The seabed is simulated by the Biot's poro-elastic dynamic model. Both models are linked together to form the PORO-WSSI (3D) model. Based on the newly model, the soil permeability and the degree of saturation significantly affect the wave-induced oscillatory pore pressures.

Recently, coastal erosion in the form of inertial cavitation has been generally accepted. Air pockets in an incoming wave are forced into the surface of the coastal cliff, and then the force of the wave compresses the air pockets until the bubble implodes, giving off various forms of energy that erode the rock. This paper studies the behaviour of a cavitation bubble in a compressible liquid near a rigid boundary, when it is subjected to a harmonic wave. Because of the extremely short life time of the bubble, we assume the wave pressure acting on the bubble surface is constant. An approximate perturbation theory by using the method of matched asymptotic expansions is used to incorporate the influence of the compressibility of the liquid. The rigid boundary creates an asymmetry in the flow field that causes bubble to collapse non-spherically. A numerical model based on the mixed Eulerian-Lagrangian (MEL) method and the boundary integral method (BIM) for bubble dynamics in a weakly compressible liquid is developed. The shock wave pressure caused by the high speed jet hitting on the rigid boundary is found to be of sufficient magnitude to initiate erosion of the loose boundary.

An experimental study of the effects of pneumatic chambers on the performance of box-type floating breakwaters is reported. The floating breakwater is moored by a slack mooring system. It is found from our experiments that the pneumatic chambers can increase the energy dissipation and reduce the transmission coefficient significantly for medium and long waves, but have insignificant effects on short waves. Information on the motion responses and air chamber pressures are also reported.

The present paper applies the wave pump concept to a flooding event at Lake Conjola, Australia. We explain how the raised water level in the lake was caused by waves with large height and very long period pumping water into the lagoon across a berm separating the lagoon from the ocean with the nominal wave set up effects. Outflow through the entrance channel, modeled as critical flow over a weir, results in less agreement with measurements compared to that of approximating it as a channel with finite length. An inverse analysis indicates that the entrance scoured out to become more efficient during the wave event, returning to normal cross section after the event. This insight was utilized to adjust the entrance area in a forward model to get optimal fit with measured water levels. Finally, the wave pump concept was confirmed using a two node model that reflected the actual surface areas of two lakes in series.

This paper presents an experimental study of the vortex-induced vibration (VIV) of a spring-supported rigid cylinder, which is placed near a plane wall and could vibrate in the transverse direction to the free stream. It is considered as an extension of the widely studied VIV phenomenon of a stand-alone cylinder in steady uniform flow. The effects of varying the gap height (defined as the distance between the cylinder bottom and the wall surface) on the VIV characteristics, including the vibrating frequency and amplitude of the cylinder, are examined in detail. The motion of the cylinder and its wake patterns have been measured using Particle Image Velocimetry (PIV), in conjunction with direct measurements of the hydrodynamic forces (drag and lift) on the cylinder using a piezoelectric load cell.

This paper describes the O-tube, which is a new facility for submarine pipeline stability research. The O-tube comprises of a closed loop channel of water driven by an impeller. The impeller runs at a constant speed to provide steady flow and at sinusoidal speeds to generate oscillatory flows. The O-tube combines the capabilities of a conventional open channel flume (which provides steady current) with a U-tube (which provides oscillatory flow). The primary function of the facility is to physically model the stability of pipelines at a relatively large scale (typically ⅕) for large diameter pipelines (e.g. 40 inch gas trunklines) and at full scale for small diameter pipelines (< 10 inch). The specification of the motor and impeller is such that typical 100-year tropical storm conditions in 40 m to 80 m water depth on the North West Shelf (NWS) of Western Australia are comfortably generated within the performance envelope of the facility.

According to the feature of the project and the sea area where the LNG terminal project lies, a 2-D tidal current mathematical model with irregular triangular grids is set up in this paper. Verification and validation are carried out fully against the measured data of 2009. A numerical simulation of tidal current is made after the project of LNG terminal in Yuedong area. In this paper, we analysis the detailed variation of the tidal current after the implementation of the project, such as: local flow field flow condition in front of wharf current velocity and direction in harbor basin and channel influence scope flow along the dike cross flow in channel. We master the flow field of present situation and the flow field after the implementation of the project to provide the scientific basis for feasibility of the LNG terminal project. The results show that: though the project's effect on local flow field is obvious with the decreasing of the current velocity in the east and west of the dike and the increasing in the south of the dike, its effect on surrounding environment is limited, so it is feasible to construct the project.

Experiments for combined orthogonal wave-current flows over a movable sand bed have shown similar flow resistance when the current is parallel and perpendicular to the wave-formed ripples. This counter-intuitive observation motivated the present experiments, in which fixed artificial ripples are used to ensure a static and strictly 2D bottom roughness configuration during the experiments. An additional series of wave-current experiments over a smooth bed is also conducted in this study. The experimental results show that there is an increase in bottom roughness when the angle between ripple axis and current direction increases. The current also tends to align with the ripple axis as it approaches the bottom from above. When waves are present with near-orthogonal currents in a closed basin, it is observed that the steady current direction is ‘forced’ to change from its original mainstream direction, due to the presence of a wave-induced return current. This modification of current direction is inevitable due to mass transport associated with progressive waves, and should be considered when formulating and verifying models for wave-current interaction. For combined wave-current flows over a smooth bed, experimental results for angles of 60°, 90° and 120° between wave and current directions indicate an increase in the near-bottom mean flow when waves are present. However, the mean shear stress, when analyzed by the log profile method, is found to be smaller for combined wave-current flows than for currents alone.

The paper presents the part results of a series of physical model scale experiments conducted for the study of variation of transmission coefficient K_t due to the horizontally interlaced multi-layered moored floating pipe (HIMMFP) breakwater. The studies were conducted on physical breakwater models having five layers of PVC (Poly Vinyl Chloride) pipes with wave steepness, H_i/gT² (H_i=incident wave height, g=acceleration due to gravity and T=wave period) varying from 0.063 to 0.849; relative width, W/L (W=width of breakwater and L=wavelength) varying from 0.400 to 2.650 and relative spacing, S/D=3 (S=horizontal centre to centre spacing of pipes and D=diameter of pipe). The transmitted wave heights were measured, and data gathered was analyzed by plotting non-dimensional graphs depicting the variation of K_t with H_i/gT² for values of d/W (d=depth of water) varying from 0.082 to 0.276; and also variation of K_t with W/L for values of H_i/d varying from 0.060 to 0.400.

To simulate typhoon induced surge for the west coast of Korea, an extended grid structure from Yellow Sea to North Western Pacific was established. Numerical simulations on the NWP grid were performed by using dynamical coupling of the two models pADCIRC and unSWAN on 64 parallel processors. Computed RMS error of tidal amplitudes and phases are in very good agreement. Coupling of wave model with asymmetric wind vortex give reasonable results showing water level jump up near landfall of typhoon.

There are several bulk flux models for an ocean surface boundary layer of surface roughness and TKE flux at the ocean surface. However, these bulk flux models have not been calibrated at extreme conditions in detail. The validation for the parameterization of bulk flux models is carried out analyzing correlation between numerical and observed vertical distributions of temperature and velocity. The numerical experiments were conducted during the Typhoon Melor in 2009 at Tanabe Bay, Wakayama, Japan. It was found that the parameterization of the TKE flux has significant influences on temperature and velocity in the nearshore region. The calibrated model can be improved with the accuracy of temperature and currents against the observations about 10% to 30% near the ocean surface.

Recently, rip current became a well-known technical term in Korea. At Haeundae beach which is located on the southeastern corner of Korean Peninsula, more than 50 people were swept away by the fast-moving seaward current and rescued, on July 29 and 30, 2010. Haeundae beach draws one million visitors and more than 50 people are rescued due to rip currents every summer season. The holidaymakers, who are enjoying the waves on tubes near the shore, are unexpectedly carried away seawards, floating as far as 50 ~ 100 meters away from the shore where swimming is restricted for safety reasons. A similar situation takes place more than 3 times every summer. Therefore, rescuers have strengthened lookout measures at several spots where dangerous rip currents have occurred.

It is generally accepted that rip currents arise mostly from alongshore a variation in wave height due to wave refraction over alongshore inhomogeneous bathymetry. The field measurement for clarifying the generation mechanism was performed in Haeundae beach. In this study, we verify a rip current forecasting model, HAECUM which was installed for Haeundae beach and using incident wave conditions, we set up a rip current predictive guidance which included in the HAECUM.

This study focuses on better understandings and accurate predictions of the breaking and broken waves and associated undertow profiles especially over a submerged breakwater. Laboratory experiments are first performed in a 2D wave flume over 1:30 sloping beach with a submerged breakwater to capture the wave deformation, time-varying current velocities and vertical profiles of time-averaged undertow velocities. A newly developed numerical model is then tested against the experimental data sets. In contrast to the existing models, the present model accounts for mass conservation equations for determinations of the vertical profiles of undertow shear velocities. Furthermore, the model also introduces modified time-varying formulation of turbulent mixing length scale for turbulence closure scheme. While the laboratory experiments reveal the complex wave deformations and associated undertow properties around the submerged breakwater, the present model shows excellent predictive capabilities for simulation of the current fields under breaking and broken waves.

This paper investigates sinusoidal oscillatory flow around a two-cylinder system numerically. The cylinder configuration comprises a pair of nearby cylinders of different diameters, with the small cylinder piggybacks on the big one. The configuration is often referred to as a “piggyback” cylinder system. The large cylinder is referred as the main cylinder and the piggyback cylinder is referred as the small cylinder. Flow structures around and hydrodynamic loadings acting on the main cylinder are expected to be influenced by the small cylinder due to the hydrodynamic interactions between the two cylinders. In order to find out the influences induced by the existence of the small cylinder at the proximity of the main cylinder, simulations are carried out both on an isolated cylinder and on the side-by-side piggyback configuration cases. The simulations are carried out at Reynolds number of 800 and Keulegan-Carpenter number of 8 (both based on the diameter of the main cylinder). In the two-cylinder cases, the small cylinder is located above the main cylinder and the gap to diameter ratio (g/D, where g is the gap and D is the diameter of the main cylinder) is in the range of 0.1 to 0.5 with a uniform increment of 0.1 to investigate the corresponding influences of the gap ratio. The diameter ratio (d/D, where d is the diameter of the piggyback cylinder) is 0.2 in the present study. Hydrodynamic forces and flow characteristics around the cylinders are investigated in detail. Flow structures near the two cylinders are investigated through flow visualization. It is found that the existence of the small cylinder has profound effects on the flow structures around the main cylinder and hydrodynamic forces on the main cylinder.

To quantitatively evaluate the role of the onshore streaming, laboratory experiments were conducted under the combined asymmetric wave-current conditions. The asymmetric flows with a wave period of 5 s and a maximum onshore velocity u_max varying from 0.8 to 1.6 m/s have been applied for three well-sorted sands with different medium sand sizes. The sediment net transport rate was measured. Results show that except several cases, the onshore streaming enhanced the onshore sheetflow net transport by different extents. The streaming-induced net transport rate is found to be related to the free-stream velocity and the sand size.

In this study, laboratory experiments are conducted to investigate flow fields around floating breakwaters by using the LDV (Laser Doppler Velocimetry) system. The LDV system is a well-known equipment to measure fluid particle velocities in laboratory experiments. Although the system requires great efforts and enormous time for measurements, it can provide precise velocity fields comparing to other available equipments. Various types of drafts and shapes for breakwaters are employed in laboratory experiments to analyze a relation between flow-fields and vortex. A series of numerical experiments are also carried out by using a two-dimensional Navier-Stokes equations model. Numerically predicted results are compared with experimental measurements.

In this study, to clarify the relationship between water level variation and turbulence of flow, field observations were carried out in Omaehama beach, Nishinomiya City, Hyogo Prefecture, JAPAN. In each observation, wind speed and its direction, water level, wave height, flow velocity and its direction were measured in the vicinity of shoreline. The data of wave height was transformed to the velocity by using a liner filter theory and examined the effect of boat wave and wind one on turbulence of flow. The transferred velocity from wind wave was coincided with the turbulence of flow, however, that from boat wave was not so good. From the results of this study, we can see both boat wave and wind one are the significant factors of water level variation in urban semi-closed water area.

An important primary mechanism for Langmuir circulations (LCs) is the Craik and Leibovich (CL-II) hydrodynamic instability mechanism. The widely accepted CL-II mechanism explains LCs as a consequence of current and wave interaction. However, the original stability analysis of CL-II mechanism quantitatively fails to predict the spacing (streaks occur where down-welling occurs and thus represent the spacing of two rolls) of LCs in ocean. The predicted preferred spanwise wave number corresponding to maximum growth rate of unstable mode is much larger than that observed in ocean. Anisotropic turbulence eddy viscosity is proposed to modify the CL-II formulation. The large horizontal eddy viscosity effectively dissipates LCs with large spanwise wave number and be able to predict preferred spanwise wave number well consistent with ocean.

In the time domain and frequency domain, the paper studies the influence of the heave plate geometric parameters and layout changes to the Truss Spar's hydrodynamic performance. First, it introduces the basic theory and method which are used in solving the hydrodynamic loads, the hydrodynamic coefficient and the nonlinear time domain response. And then, a number of different heave plate structures of Truss Spar Platform 3D hydrodynamic models are established. These model's hydrodynamic characteristics are discussed and the hydrodynamic coefficients are obtained by using three-dismensional potential flow theory. The relationships between the changes of quantity, distance, thickness of the heave plates and the platform's hydrodynamic coefficients is discovered by analyzing the information. At the same time, it gives coupled analysis to the Spar platform under regular wave in time domain, and also gives analysis to the influence of heave plates' parameter changes on platform's time domain motion. This paper can provide technical guidance for the optimal layout of heave plate and has a certain practical reference value.

A three-dimensional numerical model combined the Realizable k-ε turbulence model and the porous media model is established to simulate the flow field around a fishing net under current. The unknown porous coefficients are determined from the experimental forces on the net and flow velocities and the attack angles using the least square method. Therefore, the porous media act the same water-blocking effect as the net. This numerical model is applied for the simulation of the flow field around a plane net under current and the numerical results are compared with the data obtained by physical model tests. The comparisons show that the velocity magnitude of the numerical simulation agrees well with the experimental data with different attack angles. It is indicated that this numerical model is applicable for the simulation of the flow field around a fishing net. This study can be valuable for better knowledge of the flow characteristics around fishing net cage.

Multi-body dynamic simulation method is applied for the coupled dynamic analysis of a FPSO with soft yoke mooring system. In the analysis, the FPSO and soft yoke mooring system are modeled as four rigid bodies of six degrees of freedom. The transfer functions of the first-and second-order wave force and hydrodynamic coefficients of the FPSO are calculated in the frequency domain. Then, the coupled dynamic analysis of the soft yoke moored FPSO under wave environment is carried out in the time domain. To better understand the contribution of the second-order difference frequency force to the FPSO response motion, cases with different water depths and wave spectrum peak periods, are analyzed. Some useful conclusions could be drawn.

Free-surface jets play an important role in environmental engineering and have been incorporated in many engineering applications. Characteristics of the jet-induced water surface perturbation may be used for assessing the effect of pollutant discharge into watercourse (jet dilution), remotely detecting the wakes of ships, or improvement of water quality. Published studies are mainly focused on the hydraulic characteristics of surface jets in terms of both mean velocity and turbulence. In this study we aimed to utilize surface jets as a potential driver to enhance the re-aeration process so as to improve water quality throughout a water column, and specifically the concentration of dissolved oxygen (DO). This paper presents work done on the spreading characteristics of surface jets. Initially, an investigation on the effects of Reynolds number and air-water interface on the vertical spreading of surface jets was carried out. The Reynolds number (based on the circular jet diameter (d0) of 6mm) ranged from 1,500 to 6,000, and the normalized jet depth (h/d0) varied from 0.55 to 1.94, where h was the distance from air-water interface to jet centre line. The flow fields were measured using the Particle Image Velocimetry (PIV) technique, which had a resolution of 1600×1200 pixels and a frame rate of 15Hz. To characterize the jet-spreading behavior, we mapped the flow path traced by the core of the jet (enveloped by velocities, u≥10% of jet maximum velocity, Um). This core was well-defined when presented in terms of d/dm and x/xm, where dm and xm were the jet maximum penetration depth and the corresponding distance from jet exit, respectively. The findings of this study show that an increase in Reynolds number results in an increase in the spreading width of the surface jet (h/d0 ≤ 0.55) in the downstream direction. The findings also revealed a well-defined relationship among the parameters investigated.

Reichardt's momentum transport hypothesis is an interesting turbulent closure model which provides a theoretical basis for superposition of momentum flux from multiple sources of flow. The point-source method, an offshoot of Reichardt's hypothesis, can be applied to a variety of jet flows. The method has a distinct advantage over the conventional approach as it predicts the entire flow field based on a single spread coefficient. To use the method with confidence, the point source technique is being validated against CFD results of different kinds of jets.

The flow dynamics of a single jet and four tandem jets in cross flow were simulated using the Computational Fluid Dynamics (CFD) code Fluent. The realizable k-ε model was used to close the Reynolds-Averaged equations. The flow characteristics of the jets, including jet trajectory, velocity field and turbulent kinetic energy, were compared at the jet to cross flow velocity ratio of R = 2.38 − 17.88. The single jet is found to penetrate slightly deeper than the first jet in a jet group at the same R, although discrepancy decreases with decreasing R. The way that the velocity decays along the centerline of the jet is similar for a single jet and the first jet in a group, and the speed of the decay increases with decreasing R. The downstream jets in a group behave differently due to the sheltering effect of the first jet in the group. Compared with the first jet, the downstream jets penetrate deeper into the cross flow, and the velocity decays slower. The circulation zone between the two most upstream jets is stronger than those formed between downstream jets.

An experimental investigation is carried out to determine the mean cross-sectional flow structures of oblique jets released in a moving ambient. The focus is on those initial discharge angles that neither produce the double-vortex pair structure of the momentum puff region or the axi-symmetric Gaussian of the weak-jet region. For an initial discharge angle of 30°, a stretched Gaussian can be used to represent the cross-sectional flow structure. The parameters defining the cross-sectional behaviour of the flow are related to important parameters of the mean flow, such as the rate of spread.

A dynamic Large Eddy Simulation (LES) model is developed and applied to investigate the jet behaviours under three different kinds of waves, including regular (extremely narrow-band spectrum) waves, JONSWAP (narrow-band spectrum) random waves and P-M (wide-band spectrum) random waves. All the waves are ‘energy equivalent’, i.e., with the same energy density and energy flux. The quantitative comparison of jet characteristic parameters, such as the centerline velocity and the jet width, under those waves is performed. The results show that close to the discharge outlet the jet under the JONSWAP or P-M random waves exhibits a faster decay of centerline velocity and a wider lateral width compared to the jet under regular waves. However, with an increasing distance from the jet outlet, the decrease rate of centerline velocity for the jet under regular waves becomes faster, resulting in a wider jet width as compared to the jet under the random waves.

The flow-field of a dual synthetic jets actuator is numerically simulated based upon the LUO-XIA model. The results indicate the lower pressure region plays an important role on the interactions of the dual jets. The dual synthetic jets actuator produces two counter-rotating vortex pairs fore and aft. The vorticity of vortex pairs contribute to the pressure difference. The pressure in the domain of the main vortex pairs is lower than other flow domains. The stronger the vortex, the lower the pressure will be. In the near field downstream, the two jets vortex pairs are strong and entrain fluid around them and interact with each other, the saddle points are formed and the flow field is complex. And there is a phenomenon of “self-support” between the dual synthetic jets, which is owed to the pressure difference between the adjacent slots. In the far field downstream, the two jets vortex pairs are weak and the two jets merge a single, more stable jet. The model can be used to predict pollutant plumes in coastal waters.

Mixing of buoyant jets laden with solid sediments at different concentrations is studied in the laboratory. The jets discharge in an initial horizontal direction into an otherwise stagnant environment. The velocities of the fluid phase and the particle phase are measured simultaneously with particle-image velocimetry (PIV) using two cameras. Separation of the two phases is achieved by marking jet effluent fluid with fluorescent dye. Results suggest that mixing and rising of the buoyant jets are modified from the single-phase case when the sediment concentration increases. Some structures of the particle velocity fields are revealed. Discussion is made on the interaction between the particle phase and the jet flow phase.

Silt screen is a flexible physical structure that has been widely employed to control sediment dispersal at dredging sites. Previous research showed that the water column is divided into two distinct flow regions in the immediate vicinity of a silt screen: a recirculation region in the upper water layer and a fast flow in the lower water layer. The fast flow at the lower water layer that emerges from below the silt screen strongly resembles a submerged plane jet. While the slow recirculation at the upper water layer may help facilitate sediment settling, the presence of such jet-flow of high velocity at the lower water layer raises concern about the potential of sediment re-entrainment and re-suspension.

This paper presents the analyses of the hydraulic characteristics of the submerged plane-jet flow that is formed at the lee side of a silt screen. The writers conducted both laboratory and numerical study to investigate the spatial development of the plane jet after it emerged from a silt screen. In the laboratory experiments, the technique of Particles Imaging Velocimetry (PIV) was used to capture the flow field in the vicinity of the silt screen. The results obtained showed that the effects of silt screen's configuration, in particular the silt screen's penetration depth, on the hydraulics parameters of the plane-jet – including velocity distribution, flow rate distribution and turbulence distribution are significant. In addition, the applicability of classical plane jet theory on describing the flow distribution of the silt screen's plane jet was also be examined.

The objective of this research is to present an experimental study of the capture and clogging behavior of organic mud in saturated sand beds. Such work has yielded a large body of information which can be used to understand the sludge-ization of tidal flats. Key aims are to delineate the decline in permeability due to the clogging of organic mud, and to understand the restoration of permeability due to the release of organic mud. It is obvious that the permeability decreases due to the clogging of organic mud, and that this permeability finally becomes constant if there is no deposition of organic mud on the surface of sand beds. Moreover, it was found that the residual organic mud could not be completely released from sand beds by infiltration flow; thus, the permeability could not be restored to the initial permeability.

Basing on the data from four times surveys, the spatio-temporal distribution patterns and the variation mechanism of nutrients in the Yangtze estuary were analyzed. The nitrate and silicate concentration exhibited an eminent ‘double tongue’ pattern in summer and autumn, however, it moved southward along the shore in spring and winter. Phosphate concentration showed the similar ‘double tongue’ pattern in summer and autumn, but the northeast frontal zone was more west comparing to that of the nitrate and silicate. The nitrate and total dissolved nitrogen (TDN) were positively correlated in all seasons; similarly the phosphate was positively correlated with total dissolved phosphorus (TDP) and total phosphorus (TP) in all seasons. It was also found that nitrate, silicate and phosphorus all had high negative correlation with salinity, which meant that the nutrient dynamics in the estuary was predominantly governed by the freshwater discharge. The Redfield ratio analyses revealed that SiO3-Si/DIN was obviously higher in the far-shore area than the near-shore area. The DIN/PO4-P was higher than the Redfield ratio 16 in the entire study area, and it gradually decreased from near-shore to far-shore.

Due to climate change and mankind actives, especially reservoirs' operation such as Three Gorge reservoirs (TGP) and pollutions from industry, agriculture and domestic sewage in the Yangtze River basin, the nutrient flux at Datong hydrological station has significant changes in recent years. Based on the data measured at Datong station in different period, the changing trend of nutrient flux including discharge, suspended solids (SS), total phosphorus (TP), total nitrogen (TN) are analyzed. Then a three-dimensional water quality model based partially on the open source code of Elfe, Wasp and EFDC are developed to simulate the C, N, P, Si cycling processes. The model is applied to the region from 120.6°E to 124.5°E and from 29.5 °N to 32.5 °N, including Yangtze estuary, Hangzhou bay and two important fishing grounds named Zhoushan and Lvsi. The upstream boundary condition at the Tianshenggang station in the 3D model are obtained by a 1D river water quality model which covers the region from Datong to Wusong using the related inflow at the Datong station. The downstream boundary conditions at open sea are given reasonably by a coarse grid model which including East China Sea. The measured data of Yangtze Estuary and Hangzhou Bay from 2004 to 2005 after TGP project are used to verify the model. The results show that the suspended sediment decreases continuously from annual value 4.6×10⁸ to 2.6×10⁸ in 2003 and then fall further to 1.3×10⁸ ton in 2008. TP and TN have a rising trend because of increasing pollution load, especially from the middle and lower reach of Yangtze River in recent years. The variation of inflow flux of nutrient matter has great influence on the concentration of nutrients in the front of Yangtze delta where confluence region of Yangtze main inflow and upwelling from the out sea exists.

Marine ecosystems in general and Phytoplankton in particular are influenced by the variability in features such as sea surface temperature (SST), advective processes (upwelling and upper ocean mixing), mixed layer depth, horizontal and vertical transport, and ecological dynamics. Chlorophyll (chl-a), the major photosynthesis constituent in the phytoplankton influences the colour of ocean water. Remote sensing of ocean colour helps to monitor the variation in biological properties of the ocean on a larger spatial scale. The present study, related to north Indian ocean, deals with a multivariate statistical analysis to study the seasonal variation of chlorophyll with variables such as Sea Surface Temperature (SST), Mixed Layer Depth (MLD) and Nitrate. Remote sensed data was used for Chl-a (Sea-WiFS) and Sea Surface Temperature (MODIS-Terra) while for nitrate and mixed layer depth, NASA Ocean Biogeochemical Model (NOBM) derived data was used. The region of study corresponded to four different zones: i) North eastern Arabian Sea, ii) Southern Arabian Sea, iii) Western Bay of Bengal and iv) Andaman Sea. The region of Northeastern Arabian Sea was found to be biologically more productive compared to the Southern Arabian Sea during the winter monsoon (FMA) as it showed large variation of chlorophyll content mainly due to winter cooling and convection overturning. The region in the Southern Arabian Sea showed high chlorophyll content during the summer monsoon (JAS) mainly due to the upwelling. The region in the Bay of Bengal showed high chlorophyll content during the summer monsoon but much lesser than that of Arabian Sea due to the stratification of layers. The region in Andaman Sea showed high chlorophyll concentration during the winter monsoon mainly due to coastal upwelling. The time series monthly data from 2001-2006 of Chl-a, SST, MLD & nitrate was studied simultaneously in all the zones through a multivariate statistical analysis. The correlation between Chl-a and SST was negative in all the zones. The multivariate regression analysis using all the data variables showed improved correlation coefficient between the observed and regressed chl-a data in all the zones.

The potential impacts of oil and gas production activities on marine environment and ecological habitats are of growing concerns. This study presents the effect of oil and gas production activities induced mud contamination on meiobenthic community, and the interactions between meiobenthic and cohesive sediments in the Campeche Shelf, Yucatan, Mexico. The meiobenthic community has potential merits in environment monitoring, because it is not affected by physical disturbance to the same degree as macrofauna, and is more stable than macrofauna but with a shorter generation time, and moreover, its life cycle is spent entirely within the sediment. The field investigations and data analyses showed that one of the key factors seriously affecting the study area is the deposition of a cohesive clay layer, bentonite, introduced from the oil production sites. The occurrence of such bentonite clay significantly changed the natural sediment granulometry as observed in the grain-size frequency distribution where a narrow peak in the size fractions between 2 and 4 μm was predominant. Such peak occurred frequently in the area surrounding the oil production sites. Contrary to what may be expected, the increase of clay content had no influence or even had a negative influence on the density of nematodes. The nematode to copepod ratio normally would increase when the content of fine fractions increases (or with decreasing particle size). However this study showed that the nematode-copepod ratio increased with the decreasing clay content. The observed contradistinctions may be explained by the deposition of bentonite clay that was artificially imported to the study area by oil and gas production activities and caused a lagged impact on the meiobenthic community. This study showed that the interactions between meiofauna and cohesive sediments as an indicator can give valuable information on environmental changes and provide a better understanding of the impact of oil and gas production activities on the marine benthic realm.

This study simulates atmospheric environments at Osaka bay area of Japan using the numerical weather prediction with highly accurate sea surface temperature (SST) data from the satellite. A series of numerical experiments for understanding urban heat island at Osaka bay area is conducted considering latest information of land use classifications, SST and an urban canopy model. The accurate daily information of SST at Osaka bay improves the daily temperature at the center of Osaka city. In addition, the one degree SST increase has impact to 0.6 degree increase of maximum temperature at the center of Osaka city.

Salt marshes are distributed along more than 400 km of the Jiangsu coast in Eastern China, which are regarded as important habitats and serve as coastal protection as well. Previous research has proven that salt-marsh vegetation can reduce current velocity and dampen waves by its stems and leaves. Reversely, hydrodynamic forces also have a significant influence on the growth of salt-marsh vegetation. To study the interaction between hydrodynamics and salt-marsh development on the Jiangsu coast, a 2D schematized model has been built by using a new interactive structure between flow, wave and vegetation modules of the process-based model Delft3D. In the hydrodynamic simulations, the impact of vegetation on waves and currents is quantified. In the vegetation growth module, the development of salt marshes is influenced by inundation time and shear stress from hydrodynamic simulations. The feedback loop is completed by hydrodynamic modules receiving the newly updated data of salt-marsh field from the vegetation growth module. The results show that wave height and current velocity are significantly influenced by vegetation. Reversely, the dynamics of marsh vegetation greatly rely on hydrodynamic conditions. Consequently, this interaction between hydrodynamics and salt marsh induces temporal variations of each other. In the model, the salt marsh is especially sensitive to the waves. Though wave height is relatively small on the Jiangsu coast, in terms of bed shear stress, waves may be of great importance to the development of salt marsh.

It is well known that plankton distribution patterns on the ocean surface are dependent on the coupling between plankton population dynamics and physical ocean mixing. The population dynamics describe the biological/ecological interactions among nutrient, phytoplankton and zooplankton. Physical advection by ocean currents affects location and concentration of the biota, which influences population growth. In this study, a model that couples plankton population growth and physical ocean mixing is used to simulate a plankton bloom in the Gulf of Alaska. The contributions of population growth and ocean mixing to the patterns and the evolution of spatial structures of plankton distribution are identified. The study found that the patterns of plankton structures on the large scale can be explained by mixing by ocean currents, whereas local distribution of plankton is more dependent on small-scale turbulence and plankton population dynamics. The method developed in this study provides a useful tool to monitor and study pelagic plankton distribution in the ocean and the knowledge obtained is useful in ocean fishery resource management.

A coastal dike for protecting the wetland was set back in 2004 near the mouth of the Maite River flowing into the Nakatsu tidal flat. Monitoring surveys were carried out between 2005 and 2009 after the setting back. During the observation period, Typhoon No. 5 hit the coast on August 2, 2007, resulting in the increase in tide level up to DL+4.7 m, which was a maximum since 2000. Owing to the storm surge, shoreward sand transport occurred and a high berm with a height of DL+5.02 m was formed with the recession of the foreshore by 5 m. No changes were observed in the wetland and its environment was maintained despite the storm surges, suggesting that the setting back was useful for protecting the wetland against storm surge.

Submarine groundwater discharge (SGD) potentially contributes comparable amounts of nutrients compared with that of river runoff. It is imperative to understand the dynamics of SGD to be able to adequately quantify nutrient loading into coastal marine environment. Electrical resistivity tomography (ERT) and radon monitoring were used to characterize submarine groundwater discharge (SGD) dynamics in Shiraho Reef located in Ishigaki Island, Okinawa, Japan. Shore-parallel and shore-perpendicular ERT transect surveys were conducted to identify seepage zones. The ERT profiling was conducted repeatedly over high tide and low tide. Simultaneously, continuous radon monitoring was made in order to estimate SGD rates. These measurements were then compared against each other to elucidate on the possibility of estimating groundwater flux from ERT measurements alone. Shore-parallel ER profiles showed the presence of several groundwater seepage zones during low tide only. These zones corresponded with relatively higher ²²²Rn activities measured from grab samples taken along the ER transect. On the other hand, the shore-perpendicular ER profiles showed that SGD mainly occurs at the beach-nearshore reef interface, though seepage may also occur in pools of water formed in low tide. Comparing ERT and radon-estimated fluxes, increases in radon inventories corresponded well with higher increases in ER values.

Granulated coal ash has been used as a covering material to restore the water environment in closed water areas in Japan, where the bottom sediment was heavily deteriorated by organic substances. Hydrogen sulfide content in pore water of granulated coal ash covering layer can be improved significantly. The numbers of bivalves, Tapes japonica and Scapharca subcrenata which are important fisheries resources, were significantly recovered 2-3 years after covering the granulated coal ash. This means, the oxygen codition can be kept by covering granulated coal ash. From these results, the granulated coal ash is an effective material to restore water environment and bivalve habitat condition.

The reclamation in the northeast of Zs Island was begun in Dec 2004, consisting of sea embankment and sea filling. Until now sea embankment have been completed while sea filling engineering hasn't been implemented yet, resulting in the form of half-enclose bay. By analyzing the data of phytoplankton, zooplankton, benthos and intertidal benthos of 1981, 2003, 2006 and 2007, the changes of ecosystem and the wetland due to the construction of sea embankment were showed in this paper including species richness, dominant species, density, biomass, diversity index, evenness index and richness index etc. From 2003 to 2006, the species richness of zooplankton and benthos decreased, increasing from 2006 to 2007, the species richness of phytoplankton increased from 2006 to 2007, while the species richness of intertidal benthos increased consistently from 2003 to 2007. The cell abundance of phytoplankton and individual abundance of zooplankton decreased consistently from 2003 to 2007. The biomass of zooplankton, density and biomass of benthos increased from 2006 to 2007. There was a little difference in density of intertidal benthos between winter of 2006 and winter of 2007, but the biomass of intertidal benthos in winter of 2007 was much more than that in winter of 2006. Especially the density of intertidal benthos in winter of 2007 was much less than that in winter of 2003, but the biomass of intertidal benthos in winter of 2007 was more than that in 2003, which shows that the macro intertidal benthos could generate during the period of sea embankment construction. It is 2006 that is turning point for marine ecology in the northeast of Zs island. Phytoplankton, zooplankton, benthos and intertidal benthos began adapting the environment after 2006. With the construction of siltation promotion embankment, the boundary of wetland has been expanding, leading to a better living environment for the intertidal benthos. After making on-the-spot investigation, we find the turbid seawater with high suspended sediment concentration becomes clearer than the seawater before the construction of sea embankment. That is to say, constructing the sea embankment without sea filling engineering could create a better environment for some ecosystem in part comparatively. But the sea filling would transform the ocean environment to the terrestrial environment, resulting in the ocean ecosystem damaged thoroughly.

Shallow areas located along enclosed coastal zones and river deltas near densely-inhabited districts have been damaged and have become sludge areas, due to the deposition of organic mud. This paper aims to explain the properties of granulated coal ash, and to review some achievements of the application of granulated coal ash in the improvement of marine enviroment and the purification of sludge. It is obvious that granulated coal ash has a capacity in the reduction of malodorous components, such as hydrogen sulfide, and methyl sulfide. Furthermore, the purification of sludge, the regenerations of habitat condition of clams and coastal environment, appeared after the application of the developed methods using granulated coal ash.

In this research, an integrated cellular automata (CA) and support vector machine (SVM) model was developed to model the concentration of chlorophyll a in Bohai Bay using remote sensing data. In order to take into account the spatial heterogeneity and local interaction of the blooms, cellular automata paradigm was implemented. The SVM was used here to constructing nonlinear transition rules for CA, for its better capacity of dealing with nonlinear complex relationships. The CA-SVM model was established with three different cases, which reflect the effect of 8-neighbouring cell of chlorophyll a concentration, the spatial position of the cell, and external factors such as SDD, SSC, SST. The model was calibrated and verified by remote sensing data of Bohai Bay. Through this study, it is shown that the spatial position, and external factors such as SDD, SSC, SST have a great effect on the distribution of chlorophyll a, and the proposed CA-SVM model could be preferably to simulate and predict the concentration of chlorophyll a in Bohai Bay, and capture the non-linear information in ecological processes.

In this paper, a SEM-BN model is established to model chlorophyll a in Bohai Bay. The structural equation model (SEM) method has the advantage to investigate complex networks of relationships and has the disadvantage to predict with new data. On the contrary, the Bayesian networks (BN) method can produce good prediction accuracy with incomplete data sets, but it is limited in identifying the true and false relationships among factors. In our study, the two emerging tools are combined to model chlorophyll a in Bohai Bay. By using SEM, the relationship between the phytoplankton dynamics and coastal environment variables during the summer period in Bohai Bay is hypothesized and tested. And by using the BN, which is built based on the structure of SEM, the concentration of chlorophyll a is simulated. The result of simulation shows that the SEM-BN model has great performance, and shows good promise for future environmental modeling efforts in other regions.

Based on wave physical model test of Yantai West Port, the wave energy concentration phenomenon and control measures in limited sheltered basin area are introduced. The mooring conditions are not improved as expected and deterioration in part region in Yantai West Port after the outside breakwater constructed. Even some slide and other facilities construction are damaged by the wave. Through physical model test and theoretical analysis, the reasons of the construction damaged are found, that is the wave energy concentration. The prevenient research shows that the wave energy concentration has related with many factors that include the rate of sheltered area scale (a) and wave length (L), the formation of construction, reflection wave and stem wave, etc. In this physical model, the port has already been constructed, so the rate of a/L can't be altered and other ways must be found to reduce or remove the wave energy concentration. During the test, the stem wave appears near the LPG berth, and it is the main wave energy that diffusing into the limited sheltered basin. The different control measures are studied that includes the way to reduce wave energy diffusing into the limited sheltered basin area and the way to absorb wave energy at the wave energy concentration area, in the physical model. And by the two ways, wave energy concentration disappears, and wave becomes calmness in the limited sheltered basin area. It may serve as reference for similar projects.

The performance of sluice caisson of tidal power plant was investigated by performing a laboratory experiment in a planar open channel. By installing 1/70 scale model of the sluice caisson in the planar open channel, with the sloping topography in front of and behind the sluice caisson, the water discharge capability was estimated with five different flow rates and three different water level conditions. By analyzing the experimental results, the relationship among the flow rate, head difference, and the discharge coefficient was found. The obtained discharge coefficient values were significantly smaller compared to the result of a previous study performed in a two-dimensional open channel.

The rotor initially converting the flow energy into rotational energy is a very important component that affects the efficiency of the entire system. The rotor performance is determined by various design variables. The power generation is strongly dependent on the incoming flow velocity and the size of the rotor. To extract a great quantity of power, the tidal current farm is necessary with multi-arrangement of devices in the ocean. However, the interactions between devices also contribute significantly to the total power capacity. Therefore, the rotor performance considering the interaction problems needs to be investigated to maximize the power generation in a limited available area. The downstream rotor efficiency is to be affected by the wake produced from upstream rotor. This paper introduces the performance of downstream rotor being affected by wakes from upstream rotor which demonstrates the interference for various gabs between devices.

A control and monitoring system (CMS) for the real-time control and data acquisition of an oscillating body type wave energy converter (WEC) has been developed and tested successively. The 2kW class WEC is the prototype of 50kW class target system. The CMS of the WEC is designed to control and monitor the motion of the wave energy extracting bodies and power takeoff unit of the WEC. The CMS consists of local and remote systems, which communicates each other through a wireless local area network (LAN) and/or a commercial CDMA protocols. The local system of the CMS gathers data from the WEC and analyzes the data for the precise monitoring of the WEC condition, and then control the WEC by sending control signals to the actuators. The performance of the CMS has been verified through a series of sea trial tests.

The highest tides in South Korea are found along the northwest coast between latitudes 36-38 degrees and the number of possible sites for tidal range power barrages to create tidal basins is great due to irregular coastlines with numerous bays. At present Lake Sihwa tidal power plant is completed. The plant is consisted of 10 bulb type turbines with 8 sluice gates. The installed capacity of turbines and generators is 254MW and annual energy output expected is about 552.7 GWh taking flood flow generation scheme. Three other TPP projects are being progressed at Garolim Bay (20 turbines with 25.4MW capacity), Kangwha (28 turbines with 25.4MW capacity), Incheon ( 44 or 48 turbines with 30 MW capacity) and project features will be outlined. The introduction of tidal barrages into four major TPP projects along the Kyeonggi bay will render wide range of potential impacts. Preliminary attempts were performed to quantify these impacts using 2D hydrodynamic model demonstrating the changes in tidal amplitude and phase under mean tidal condition, associated changes in residual circulation (indicator for SPM and pollutant dispersion), bottom stress (indicator for bedload movement), and tidal front (positional indicator for bio-productivity) in both shelf scale and local context. Tidal regime modeling system for ocean tides in the seas bordering the Korean Peninsula is designed to cover an area that is broad in scope and size, yet provide a high degree of resolution in strong tidal current region including off southwestern tip of the Peninsula (Uldolmok , Jangjuk, Wando-Hoenggan), Daebang Sudo (Channel) and Kyeonggi Bay. With this simulation system, real tidal time simulation of one-month (two spring-neap cycles) was performed to estimate spatial distribution of tidal current power potentials in terms of power density, energy density and then extrapolated annual energy density

The design methodology of the sluice caisson structure is one of important factor that is close related to the efficiency in tidal power generation. When the sluice caisson is designed to maximize the water discharge capability, it is possible to minimize the number of sluice caissons for attaining the water amount required for achieving the target power generation, which results in reduction of the construction cost for the sluice caisson structure. The discharge capability of sluice caisson is dependent on the geometrical conditions of an apron structure which is placed in both sides of the sluice caisson. In this study, we investigated numerically the variation of water discharge capability of sluice caisson according to the geometrical conditions of apron. Flow fields are simulated with FLOW-3D software using VOF method.

Inspired by nature, flapping-type tidal power generators have been proposed since the early 21th century. The improvement of power generation ability is one of key issues in commercializing the flapping-type generators. According to the researches of flapping-type propulsion, fluid-dynamic characteristics have been improved by morphologies such as the corrugation of scallops or the chamber of insect wings. In this study, we explore the effect of the corrugation and chamber, by mimicking a scallop, on the power generation ability. Two dimensional Navier-Stokes simulation is utilized for the numerical analysis of the morphological effects. From this analysis, we find that the morphological effects are also considerable in the flapping-type power generators, and suggest an optimal morphology in terms of the corrugation and chamber.

The preliminary results of physical and numerical experiment are presented for investigating the performance of the tidal stream turbine system, which is under development for application to the gap between the bridge protection structures. The advantage of this system is acquisition of high flow velocity due to flow acceleration at the gap which allows efficient power generation from the tidal stream turbine.

Dynamic behavior characteristics for the mooring line of a floating wave energy converter with the numerical study are analyzed. The case studies for the different top excitation in the horizontal and axial direction induced by surge and pitch motion of a floater are carried out. On the operational condition, the height of tension variation of a mooring line by the top excitation in the axial direction at the top of a mooring line shows almost 2.5 times than it in the horizontal direction. That can be an important parameter to determine the connection point between a floater and top point of mooring line. It is found that the top excitation with long period by slow drift motion of a floater induces the large excursion resulting in large top tension of a mooring line. In the design of a mooring system point of view, the different natural frequencies according to excursion distance and static configuration should carefully be considered

A 50kW class rotating body type wave energy converter (WEC) composed of two floating bodies and a power takeoff (PTO) unit is designed based on the experimental and simulation studies. As a wave energy extractor, the body is equipped with a variable liquid-column oscillator (VLCO) having a liquid filled U-tube and air chambers. The PTO converts the rotational moment introduced from the relative motion of the hinged bodies to a hydraulic power by means of a cylinder. A high pressure accumulator, a hydraulic motor and a generator are provided for the PTO to convert the hydraulic power to a high quality electric power. Control laws for adjusting the oscillation period of the VLCO, and regulating the pressure and flow rate of the working oil pumped by the cylinder are proposed for the efficient operation of the WEC.

Offshore wind energy is one of the most important new energies that are developing fast in the world. There is an in-neglecting problem in offshore wind turbine system similar to other offshore structures that the offshore wind turbine system is in the severe sea states. Especially in the regions which influenced by tropical cyclones, the strong winds, surges and huge waves induced by storms will lead to the structure failures and make large losing. In meteorology field, more attentions are paid in the mechanism of the storm process than the effect of storms to the structures. While in engineering field, the combination of wind, wave and current with some return period is selected according to the design code, then the response analysis of structures will be performed. The influence of storm induced extreme sea environment factors to the wind turbine system is not considered reasonably. According to the previous research, Multivariate Compound Extreme Value Distribution (MCEVD) is effective in the joint probability prediction of extreme sea states. It also can be used in the probability analysis of structure stress. And grey model is adaptive for the prediction based on short stochastic sample series. It can be used in reliability analysis of offshore structures. In this study, numerical simulation, probability analysis and prediction based on theory of grey system are used to propose a nested model for the reliability analysis of offshore wind turbine system. The model is consisted of MCEVD, Grey Markov Chain Model (GMCM) and structure dynamic response model. Using the nested model, the influence of tropical cyclone to the offshore wind turbine system in the South China Sea is analyzed.

In order to develop techniques for utilizing clean and renewable hydro energy, Korea has been conducting a study on in-stream hydro energy system. Field measurements have been performed in a discharge canal at the Hadong Power Plant Company. Helical-type hydro turbine has been selected on the basis of field conditions and results of preliminary experiments. The turbine jacket, kinetic energy transfer system and electrical facilities for the in-stream hydro energy system (IHES) are designed. The established IHES has been successfully operated. The present application to a discharge canal is advantageous since water current speed and temperature in the canal is decreased and adverse impacts on nearby ecosystem can be improved.

In order to analyze incompressible two-phase flow, level-set method is applied on the artificial compressibility (AC) method in which the incompressible Navier-Stokes (INS) equations are directly solved for velocity components and pressure. Level-set function is defined as a signed distance function from the interface between gas and liquid. Numerical model for a two-phase flow is developed on general curvilinear coordinate. The numerical study is applied for a dam break problem and the numerical result is in overall agreement.

The use of unstructured grids in hydrological, hydraulic and water quality modelling offers great advantages in fitting complex model domains by applying combinations of linear, triangular, quadrilateral and higher order cell shapes. The flexibility of the approach is demonstrated by describing models developed for part of the Kam Tin Main Drainage Channel in Hong Kong and for the San Francisco Bay - Sacramento Delta in the USA.

A three-dimensional RANS (Reynolds-Averaged Navier-Stokes equations) - VOF (Volume of Fluids) model is presented for numerical simulations of a solitary wave flow around a fixed 3D vertical circular cylinder based on the OpenFOAM solver. The RANS equations with the blended SST k–ω turbulence model are solved by using the finite volume method. The free-surface is captured by the VOF method. The Pressure Implicit with Splitting of Operators (PISO) algorithm is used in the calculation procedure. The wave elevation within a cylinder radius distance around the cylinder is monitored at several particular positions. The flow field is investigated including the velocity and pressure distributions. The obtained numerical results of wave run-up and scattering around the cylinder are compared very well with the measurements from experiment model tests.

The dynamics of flow involved with surge bore propagating over a slope is studied numerically using a fully three-dimensional (3D), incompressible, two-phase flow Navier-Stokes (NS) solver coupled to a LES turbulence model. A high-resolution STACS-VOF method is applied to capture the interface between the air and water phases. The computed uprush shoreline motion and the tip of runup water surface compare favorably with experimental data. Numerical results are also presented for the instantaneous flow field, recirculation regions, vortex tubes, and maximal bed shear stress. The results indicate that the flow phenomena are very complicated after the bore breaks.

In this study, we developed Gaussian source functions on an arced band to generate incident waves in the extended mild-slope equation. Numerical experiments were conducted for waves propagating on a flat bottom and also waves scattered by a vertical cylinder. The numerical results showed that the technique of wave generation using on an arced band causes negligible diffraction problem near the sponge layer.

The Bohai Sea is a semi-enclosed inland sea in northern China which has been polluted these years. The wave, tide and storm surge are the most important dynamic processes in the Bohai Sea, these three dynamic factors play an important role in the water exchange of the Bohai Sea, but few researches has been done about the influence of the wind on the water exchange in the Bohai Sea. In this study, some concepts and models for water exchange in the coastal sea are introduced. Half-life time, simulated by a dispersion model, is chose to represent the exchange ability of the Bohai Sea. Based on the FVM method and unstructured triangular mesh, a high resolution numerical model is established to study the tide and storm surge. This model coupled with SWAN model is applied to study the combined action of wave, tide and storm surge. The coupled model, verified by measured data from the southwest coast of the Bohai Sea, is used to simulate the water exchange process of the Bohai Sea. The results show that the wind in the Bohai Sea has significant influences on water exchange results. A coupled numerical model of wave, tide and storm surge should be used when the water exchange process is simulated in the Bohai Sea.

An improved boundary treatment approach for smoothed particle hydrodynamics is presented. In this approach, the pressure of a boundary particle is obtained by interpolation using the pressure of fluid particles in the near boundary area around it, and the boundary particle pressure is used to solve the momentum equations. This boundary treatment is applied in the SPH model to simulate nonlinear sloshing in a rectangular tank. The simulated free surface elevation is in good agreement with the experimental results. This paper also illustrate that the proposed approach is superior compared to earlier approach.

The present study suggests an estimate method of currents combined with surges and tides as values of open boundaries using the Flather's condition for a 2 dimensional coupled model of surge, wave and tide considering the wave-current interactions on the surface and bottom boundary layers. We found that the present method made an improvement in the reduction of spin-up calculation duration and was more stable in comparison between other radiation conditions with currents or water levels with either fixed or variable phase speeds.

Although the 2-D numerical wave flumes have recently been applied to the wave-structure interaction system, 3-D configuration of permeable breakwaters cannot be reproduced in the method. In this study, CADMAS-SURF/3D which has been newly developed as 3-D numerical wave tank is applied to estimate the hydraulic performance of the permeable breakwater. The applicability is investigated from the comparison between experimental and calculation results, in which detailed wave absorption mechanism is also discussed.

Uniform flow past four circular cylinders in an in-line square configuration was studied numerically at Reynolds number of 270. The three-dimensional (3D) Navier-Stokes equations were solved using OpenFOAM, an open source code. The study was focused on the influence of multiple cylinders and their spacing ratio on the wake flow. The effects of gap between two neighbor cylinders on vortex shedding frequency and force coefficients are studied. Flow characteristics are observed through flow visualization of streamwise and spanwise vortices based on the numerical results. It was found that there exists remarkable repulsive force when cylinders are very close to each other, and this repulsive force disappears gradually with the increase of spacing ratio. Also, the critical Reynolds number for flow transiting from two-dimensional to three-dimension is different from that of an isolated cylinder and is dependent on gap among the cylinders.

Consisting of large arch-shaped precast concrete blocks positioned at intervals astride the pipeline, the gravity anchor system is engineered to provide secondary stabilization for large diameter offshore pipelines operating in severe metocean conditions. Bottom-seated on the seabed, however, the gravity anchor could subside into scour pits formed around it, imposing integrity risks on pipeline operations. With scour processes around gravity anchors correlating closely with the hydrodynamic behavior of flow, the present study concentrates on characterizing flow mechanisms around gravity anchors by means of direct numerical simulation. The three-dimensional Navier-Stokes equations were solved using the Petrov-Galerkin finite element method. Currents with a 90 degree angle of attack past a gravity anchor astride pipelines resting on a rigid bed was simulated at a pipe Reynolds number of 1000. The computed amplification of bed shear stresses was presented first, and compared with laboratory observations of scour patterns. Then, the responsible mean flow topology has been identified in two areas, comprising the horseshoe vortex upstream of the anchor and the lee-wake vortices.

A three-dimensional finite element model was developed to simulate the tidal current of the Ariake Sea. This model has two features. One is its use of the sigma-coordinate system for the vertical direction and the other is its application of the finite element method that employs the bubble function element to perform analysis. The tidal current of the Ariake Sea in 2007 was simulated as a numerical model test. It was confirmed that the simulated tide level represents the observed tide by comparing the data at seven observation points. However, the amplification rate of the M2 component of the tide level from Kuchinotsu to Ooura was slightly small. The result of the comparison of current ellipses in January and August indicates that the proposed model can correctly simulate the tidal current of the Ariake Sea. The simulations of the distribution of the temperature and of the salinity of seawater were confirmed by comparing their results with the observation data.

In this work, we employed the immersed boundary method and volume of fluid method to simulate the interactions between free-surface waves and submerged fixed structures. The immersed boundary method is applied to handle solid object boundaries that are replaced with a proper force in the Navier-Stokes equations imposed on the body surface. Submerged obstacles of different shapes such as trapezoids, and semicircles are investigated to validate the ability of the numerical model to simulate fluid-structure problems. The comparison between the results of the developed numerical model, available experimental data, and numerical estimations reveal a favorable agreement.

The motions of cubic armor blocks are simulated with DEM in which the shape of each element is cube. The result simulated with DEM under a simple condition including a collision is compared with a measured result. The positions of vertices in a cubic armor block before and after the collision simulated with DEM almost agree with the measured result.

In this study, three-dimensional hydrodynamic pressure model for free surface flows using a normalized vertical coordinate system is presented. Numerical models of free surface flow are developed to calculate the velocity components, the free surface elevations in the following three steps. At the first step, the vertical momentum equations are discretized by using an implicit method over the vertical direction. In the second step, the discrete horizontal momentum equations are projected on to the free surface equation. The predictor-corrector step method is used to calculate variations of free surface elevation and velocity. Finally, the hydrodynamic pressure and final velocity field are calculated. As the vertical velocity is not taken into account at the previous step, the velocity field may not satisfy the local mass conservation at each computational grid cell. In this step, the velocities and the free surface elevation obtained from the previous step are corrected to conserve the local mass balance by considering the hydrodynamic pressure in conjunction with the continuity equation. The developed model is applied to propagation and subsequent run-up process of nearshore solitary wave around a circular island carried out by Coastal Engineering Research Center (CERC), US Army Corps of Engineers. Computed results are then compared with laboratory measurements. Very reasonable agreements are observed.

A new technique to choose open boundary conditions for model nesting in hydrodynamic modeling is presented. In addition to the traditional ways to configure the open conditions, a tangential velocity component is incorporated. To verify the technique, a schematic case and an engineering case are set up. The results from overall models are well reproduced by the nested models with much less computational effort and higher resolution. The results show that the new technique has high potential to design simple, efficient and robust open boundary conditions for coastal area models.

In this study, a SPH model is preliminarily applied to estimate the interactions between a bottom-hinged wave energy converter (WEC) and free surface waves in a 2-D numerical wave flume. To estimate the capturing efficiency of a WEC in this flume, a monochromatic wave with height of 7.15 cm and period of 1.56 s based on a model scale of 1:20 of the in-situ wave conditions were adopted. The results show that the loading waves can cause the flapper to stably swing back and forth within average ranges of 16˜18 degrees. The phases could directly influence the flapper's swinging and should potentially play a key role in capturing wave energy. Comparisons of the velocity profiles at different phases further illustrate that elliptical form of water particle trajectory could directly influence the rotations of flapper. When the flapper undergoes small rotations, most of the counterclockwise vortices in the weather side and clockwise ones in the lee side have occurred around the flapper. But when the flapper undergoes large rotations, those vortices would only occur near free-surface. Meanwhile, the circulations in the lee side of the flapper have increased while those in the weather side have decreased.

The 3-D fully resolved simulations of forces on particles in oscillatory boundary layer flow over a rough bed composed of a layer of spherical particles are carried out using the lattice Boltzmann (LB) method. Two types of bed pattern are considered, i.e., hexagonal packing and cubic packing. The variation of ensemble-averaged force coefficients in one oscillatory period is investigated. The maximum of them as a function of amplitude Reynolds number and the ratio between particle diameter and the Stokes boundary layer thickness are also discussed. The expressions for them are suggested with introducing the porosity to characterize the effect of the bed pattern. Meanwhile, the role of spanwise force is shown.

In 2007, the State Oceanic Administration of People's Republic of China started monitoring the seawater intrusion in China. The results showed that seawater intrusion area in the coastal plain of Liao Dong Bay already encroached more than 4,000 km2 of land area with nearly 1,500 km2 of area in serious condition. The most remote region of seawater intrusion was situated 68 km inland from the shore of Pan Jing City. To analyze the tidal effect on seawater intrusion, a three-dimensional numerical model of density-dependent groundwater flow and miscible salt transport was developed based on SEAWAT code which combined the two commonly used groundwater flow and solute transport modeling programs of MODFLOW and MT3DMS. A simulation of 55 months (from October 2004 to April 2009) in the coastal plain of Liao Dong Bay (140 km × 119.997 km) was conducted by this numerical code. After model calibration, two prediction cases were conducted considering no-tidal and with-tidal effect for an extension of continuous 40 years starting April 2009 based on the calibration model. The results of the two cases showed that seawater intrusion area will increase in all layers and that seawater intrusion into the Quaternary layer will be significantly faster than that of the Minhuazhen group layer. In addition, most of the Quaternary layer chlorine content of with-tidal case will be higher than those under the no-tide case, especially in the area located within 20 km from the coast. The extension of seawater intrusion area encroached nearly 10 km deep in the Quaternary layer and 3 km in the Minhuazhen group layer.

Though locates at the Pearl River Delta and being a coastal city, Macao has been suffering from water shortage due to its small land area hence very limited catchment. With an increasing pace of social and economic development of the region recently, maintaining proper supply of potable water both in quality and quantity is a challenge, of which sea water intrusion during dry season is one needed to be tackled immediately. Management of the raw water resources is an urgent topic for the Pearl River Basin where Macao sits on its exit delta. Through analysis of the basin hydrological and related data, possible causes of the worsening saline-water-intrusion situation were identified. Approaches to solve this problem at basin level, delta level and local city level are being attempted; e.g. cooperating with the water conservancies in Mainland China, a new raw water intake for Macao was built further upstream, and a reservoir of high capacity is being constructed as a major supporting unit for fresh water supply during dry season. Nonetheless, a future plan including a centralized water resources and basin management system and related regulations is necessary.

Conditions of tidal bore formation in river mouths are studied. Existence of bore is determined by balance between the tidal range, river flow and morphology of the estuary. The same factors determine the intensity of mixing of fresh and salt waters and the distance of sea water intrusion. The types of water circulation and stratification in the river mouths, where bores are formed, are discussed. Characteristics of mouths of the rivers Amazon, Yangtze, Qiantang and Mezen are compared. Longitudinal bottom profile of an estuary is assumed to be one of the main factors influencing the occurrence of tidal bore.

A depth-averaged 2-D numerical model with Delft3D-FLOW is adopted to compute the salinity in the Changjiang Estuary. After well validated against the field measurements, the model is applied to simulate the salinity under the different discharges after the operations of Three Gorges Project (TGP) and Eastern Route of South-to-North Water Transfer Project (ERSNWTP) combined with various tidal ranges in the dry season. The results show the salinities decrease with the increased discharges, especially ERSNWTP with drawing 1,000m³/s water from the Changjiang, which has the highest salinity while under TGP operation the salinity is the lowest and that under the mutual effect of these two projects is between them. It demonstrates TGP can effectively alleviate the saline water intrusion while drawing 1,000m³/s water by ERSNWTP will be the opposite, but the combination of these two projects can still ease the saline water intrusion.

Large-scale hydrological observations in the Yangtze Estuary in China have been carried out in February and July, 2003. Based on these data, temporal and spatial variations of suspended sediment concentration in the Yangtze Estuary are studied from the upriver sites to the mouth sites with the mutli-methods of hydrology and statistics. The results show that (1) the reach of upriver, in whose suspended sediment concentration is stable oppositely, is controlled mainly by the runoff current; (2) suspended sediment concentration of downstream to the mouth bar is effected by some factors, for example runoff, tide, landform etc, and its variation is complicated; (3) during a tidal cycle, suspended sediment concentration is related to the current velocity, but lags to the current velocity about one or two hours. The sediment transport flux exists space-time change complexly due to the runoff and tidal current. Also the process of sediment re-suspension is more complicated in the South Passage and North Passage than other passages in respect to the salinity, and the re-suspension process is an important source of suspended sediment for maximum turbid zone. Suspended sediment re-suspension is related to the critical velocity and the eddy diffusion coefficient.

The port of Tianjin is located at a muddy coast in the western Bohai Bay. Based on field measured data and former research achievements, 3-dimension tidal flow and sediment mathematical model is set up and is used to compute sediment deposition of 300,000-ton deep-water compound navigation channel. In the paper, an empirical formula of computing sediment deposition of compound navigation channel is presented. Both methods have been applied to engineering practice. The results from empirical formula and mathematical model show that the error is about 10%.

For supporting Drainage Services Department of the Government of the Hong Kong SAR to develop a comprehensive strategy for overall land drainage and flood control in Yuen Long and North Districts, 3D hydrodynamic and sediment transport model is set up. The model deploys Domain Decomposition technique and covers the whole Deep Bay (the estuary of the Shenzhen River), the tidal sections of the rivers and drainage channels including Shenzhen River, Kam Tin River, Shan Pui River and Tin Shui Wai Main Drainage Channel flowing into Deep Bay and a part of the Pearl Estuary. As driving forces, the model takes into account waves and flow driven by wind, tide, river discharge and salt intrusion. Field surveys for wind waves, sediment concentration and especially sediment properties have been conducted. The collected data are analysed together with the existing data and used as basis for the set up of the model. The model is calibrated especially against the development of sedimentation in the Lower Shenzhen River since 2000, after a major deepening of the river. The model can be applied to predict sedimentation in Shenzhen River and tidal drainage channels for different scenarios concerning dredging strategy and river discharge regimes. The study has improved insights into the complicated hydrodynamic and morphodynamic system of Deep Bay together with the rivers and channels flowing into it.

In the paper, wind wave field, tidal current field and suspend sediment concentration field and the deposition in the channel in Lianyungang sea area are simulated based on MOHID 3D tidal current and sediment mathematical model, SWAN wind wave model. Wind field during Typhoon Wipha is simulated using the method of the Fujita.T formula and Takahashi formula. The computed results and the field measured data is compared and verification. The computed results are compared with measured data. The verification shows that the simulated result tallies well with the field observation data, thus the forecasts may serve engineering practice.

The objective of this study is to suggest a new method to estimate the settling velocity of mud flocs. The settling velocity is estimated based on the particle size distribution measured by a Laser Diffraction Particle Size Analyzer (SHIMADZU: SALD-2000J). The accuracy and validity of the suggested method were investigated by comparing the measured results with those obtained from a Monte Carlo simulation. The relative error is about 5% when distilled water was used, and it becomes equal to 10% (by 20 min) when salted water was used. Therefore, it is considered that the accuracy of the suggested method is high; that is to say, the suggested method is valid for estimating the settling velocity of mud flocs that have different organic matter contents, both in distilled water and salted water conditions.

In this paper, simulation studies are conducted on hydrodynamic changes downstream of the estuarine gates of different irrigation channel lengths with a generalized physical model. According to the characteristics of seabed in silt coastal and estuarine areas with fluid mud layers, the impact of fluid mud is taken into account in the sediment-carrying capacity formula. The simulation studies are conducted on the characteristics and laws of deposition downstream of the estuarine gates of short approach channel-river course type, short approach channel-shoal strand type and long approach channel-river course type with a 3-D hydrodynamic and sediment transport model.

Shoreward transport of sand originally supplied from the offshore zone of the tidal flat, while forming a slender sand bar, and the landing of such sand were observed on the Kutsuo coast, where a very wide tidal flat develops. Although this landward sand movement due to waves on the shallow tidal flat is part of the returning process of sand transported offshore by river currents during floods, its mechanism has not yet been studied. We investigated this phenomenon by considering the Kutsuo coast as an example. Then, we performed numerical simulation using the BG model to predict such shoreward sand movement. The observed phenomena were successfully explained by the results of the numerical simulation.

A two-dimensional numerical model for strong discontinuous flow and sediment transport was established in this paper. Based on the validation of hydrological parameters with the field data, the mathematical model simulated the current and sediment field of Jianshan reach in Qiantang River, and the spatial/temporal distribution characterization of flow/sediment were reported under different river regime conditions. There mainly exist two river regime according to the different hydrodynamic conditions. The same characterization is that the tidal wave deforms severely, and there occurs the phenomenon of formation, evolution, and development of the tidal bore in Jianshan reach of Qiantang Estuary. The maximum sediment concentration approximately occurs in flood peak, along with the flow velocity abruptly increasing. Furthermore, the time series process of the flow/sediment exist discontinuous, and the sediment concentration of the beach is much more than that of the main channel at the moment of the tidal bore arrival. The different characterization is not only the high and low tidal level but also the average velocity of flood and ebb of the bifurcating alignment more than those of the southern alignment, except the tidal range of the former less than the latter.

INBUS (Intelligent Buoy System) monitoring buoys have been operated to observe the real time suspended sediment concentration (SSC) generated by the port construction works in the Busan New Port areas since 2006. The variation pattern and/or characteristic analysis of the SSC data are carried out using the natural and artificial data components roughly classified from the treated SSC data. It is clearly appeared three typical patterns of the SSC variation, which are affected by tidal advection, rainfall-runoff and dredging works, etc.

The Port of Los Angeles conducted a pilot study in 2009 to test the use of LISST in providing real-time in-situ monitoring of dispersion of sediment plumes resulted from dredging activities. The results indicate that the LISST is a more reliable method to measure TSS compared to more traditional methods such as OBS and light transmittance. In addition, the pilot test data were used to demonstrate the use of a previously developed 3D EDFC hydrodynamic and transport model in simulating the dispersion of dredged-induced sediment plume with success.

The aim of this paper is to clarify the basic mechanism of sediment transport in Yangon River, Myanmar. Two dimensional numerical model is used to predict the water flow and sediment transport. The models for the flow and sediment transport are described in this paper. The water depth, velocity, sediment concentration and the bed level change were calculated for 4 cases near the “Inner Bar” area. It was found that the tidal current has a great influence on the sediment transport and the sediment concentration is higher at the ebb tide in both spring and neap tide condition. The flow velocities and the sediment concentration are verified against field data of Nelson (2000).

During the research process, a great deal of experiments has been conducted with the caution to investigate the sheetflow sediment transport of uniform sands under different skewed-asymmetric oscillatory flows. The experiments shows that in most of the cases with fine sand, the “cancelling effect” which cancels the net transport rates of both pure velocity and acceleration asymmetric waves may occur for waves with mixed shapes. However, in some certain conditions with coarse sand, it is observed an onshore enhancement for the mixed shape. The image analysis technique is applied so as to explore major influences of the wave shape on sand transport. Accordingly, the mechanism of sand transport under oscillatory sheetflow conditions is also studied by comparing the maximum bed shear stress and the phase lag parameter at each half cycle

In this study, nearshore sediment movement and mixing process with nourished sands along the Miyazaki coast, Japan, are investigated based on the feldspar thermoluminescence (TL) properties. Field sampling was conducted twice in Mar and Nov, 2010. River-originated nourished sand presents a larger TL intensity than that of the natural beach sand. Various sand sources are detected with respect to the TL properties. A relatively uniform TL longshore distribution was confirmed with several local TL peaks representing the sand mixing from the river supply or beach nourishment. Longshore sediment movement pattern was also revealed from the TL measurement.

A three-dimensional morphodynamic numerical sand wave model is established based on an existing model, the Regional Oceanographic Modelling System (ROMS). In the model, the vertical flow structure, which plays an important role in the formation and evolution of sand waves, is resolved by solving three dimensional (3D) Reynolds-averaged Navier-Stokes (RANS) equations with a k-ε turbulence closure. The bed slope effect on the bedload transport is considered in the model. The model is capable of capturing sand wave evolution and migration processes, which can not be modeled by conventional stability models. First, a sensitivity analysis of the model configuration is conducted, including the morphological factor, the time step and the grid size, to find out an optimal balance between the computational time and the accuracy of results. The effects of the water depth, flow velocity and sand grain size on the Fastest Growing Mode (FGM) are then studied. Finally, a migrating artificial sand wave is simulated and numerical results are presented.

Among the hard measures to combat coastal erosion, construction of groin fields remain as one of the most widely adopted. The groin field has been increasingly adopted for the Indian coast. As it is important to understand its effectiveness in taming the waves and the alongshore currents, which are the driving force of the littoral drift, it is essential to monitor the behavior of the hydrodynamic characteristics of the wave and the flow field within a groin field after its implementation. In this paper, the results from a preliminary exercise of the measurement and analysis of the wave and flow fields in a groin field north of the major port of Chennai along the South East coast of India are presented and discussed. An attempt to derive the sediment transport rate from the measured parameters using the energy flux method is made. The predicted sediment transport rates are compared with measurements from a field study that adopted a sand trap for the said purpose.

To minimize negative impacts of dredging and ocean disposal of coastal sediment on marine ecosystem and potential strife among coastal users, we suggest 1) in development projects involving ocean disposal, it should be mandatory to propose careful reuse plans in the land, and 2) guidelines of environmental assessment and consequence management programs should be developed and implemented. As a consequence, different assessment fields need to be emphasized for evaluation of the impact that both dredging and dumping might have on the sites involved. The status of current assessment procedures is examined and its problems are diagnosed. Following checklists of core assessment items are proposed as part of a revamped review process, along with improvements to the assessment system.

The magnetic anomaly induced by tsunami waves in open ocean is investigated with kinematic dynamo theory. Magnetic field will be induced by the velocity field of tsunami wave during its life cycle. Using long wave approximation, an integral solution of the dynamo problem is obtained based on the small dispersive parameter of water wave. The magnetic field induced by typical tsunami models, including single wave and N-wave, could be directly obtained from the integral solution. Through the analysis, the tsunami induced magnetic field magnitude is estimated at the order of 10 nano Tesla (nT) just over sea level and 1 nT at altitudes of several hundred kilometers respectively for 1m height waves, which also depends on other wave parameters and main earth magnetic field.

Linear shallow water equations with a prescribed forcing term are adopted to study landslide generated-tsunamis propagating on a plane beach. Seeking a solution valid for the life span of the tsunami, numerical methods are employed to evaluate integrals of the derived analytical solution. Numerical solutions are presented and discussed.