Search

With the development of inland navigation, small rivers have the demand for the construction of large-scale waterways. Taking the reach from Likou to Binlangtan of the Dongjiang River in China as an example, this paper analyzes the erosion and deposition process of the four shoals in this reach over the last 20 years; establishes a physical model dominated by the movement of the bed load for this reach; and utilizes this physical model to study the morphodynamical response of small rivers to large-scale waterway projects. The main conclusions are as follows: (1) the erosion and deposition process in the Dongjiang River can be divided into three stages: natural erosion and deposition equilibrium stage, generalized riverbed undercutting stage, and the self-adaptive adjustment stage. (2) Under the action of the large-scale waterway projects, decreasing of water levels caused by dredging can be remedied by adjusting the navigation channel bed elevation; local adverse flow caused by spur dike can be remedied by sealing the sand mining pit and shortening the dike head; the suction problem, caused by the navigable branch, can be remedied by adopting a compound channel section with multiple steps. (3) A new river regime is reshaped by waterway regulation spur dikes, and a new erosion and deposition state is formed. The layout of the navigation channels should follow the reshaped regime to reduce sediment deposition and ensure the navigation depth. This paper provides technical support for the construction of large-scale waterways in small rivers. [ABSTRACT FROM AUTHOR]

Careful planning for harbor development is vital for improving the flow of international trade and the economy of any country. Evidently, offshore breakwater reduces wave height approaching a harbor, but it is necessary to be designed as efficiently as possible. This study analyzes the development of Al-Max area as a promising new harbor connecting Alexandria's Western Harbor and El-Dekheila harbor. This development is an important step towards improving the capacity and efficiency of Alexandria's ports in order to expedite imports and exports. These objectives align with multiple UN Sustainable Development Goals (SDGs), given the fact that the specific actions and measures taken within the middle port project will determine the extent of their impact on each goal. Necessary information, such as the bathymetric map and annual wave climate were collected and analyzed. The Delft3D FM software package was used for carrying out the numerical simulations. Sheltering the whole area of the port through establishing several new offshore breakwaters, which are going to be installed at a number of locations using best-in-class designs, will partially enclose the basin containing the three harbors, while considering the existing channel of navigation. The results of the simulation prove that breakwaters with the maximum segment length and minimum clearance for navigation channels could reduce the wave height significantly. [ABSTRACT FROM AUTHOR]

Deltas are densely populated industrialized regions, and home to important ports and navigation channels. Due to human interferences, the Yangtze Estuary has experienced a significant reduction in sediment load caused by the Three Gorges Dam (TGD), as well as adjustment to local morphodynamics by the Deep-water Navigation Channel (DNC). While the dramatic reduction in sediment triggers the increased channel erosion, the deposition flux of the DNC located at the estuary mouth has little change. To explore the physical mechanism of this phenomenon, a two-dimensional model is used to establish the relationship between sediment load and the sediment budget of channels based on the bathymetry in 2016. Model results show that the tidal reach and the inner estuary have a negative sediment budget. And the seasonal characteristics of water and sediment fluxes become less obvious downstream. Sensitivity analysis shows that the influence of upstream sediment load on deposition flux decreases along the channel, with a transition from deposition to erosion occurring in the tidal reach. For the last-level bifurcation, the annual siltation of sediment in the North Passage (NP) decreases by 4.5% with low sensitivity. This is attributed to the reduction of sediment load partially mitigated by riverbed erosion and cascade bifurcations. In addition, the lateral sediment supply, which accounts for 68% of the sediment input in the NP, is stable. Overall, this study strengthens the understanding of the relationship between sediment load and artificially deepened systems, thus allowing for better management of estuarine sediment and navigation channel. [ABSTRACT FROM AUTHOR]

The depths and areas of the scour holes around spur dikes are the most concerning issues regarding spur dike design. In this study, using a moving bed experiment, the influence of traditional rock-fill spur dikes and new permeable spur dikes with different permeabilities on riverbed scour under unsteady flow was studied, and the spatial characteristics of scour holes at dike heads were analyzed. The results show that with increases in the permeability coefficient of the spur dike, the depth and area of the scour hole at the dike head gradually decreases; however, when the permeability coefficient is more than 17.6%, the depth and area of the scour hole downstream of the dike body increases with an increase in the permeability coefficient. According to comprehensive evaluation, when the water permeability is 17.6%, the stability of the spur dike is at its best. The maximum depth of the scour hole at the dike head is affected by factors such as the spur dike permeability coefficient, effective scouring time, and width bottom protection structure. On this basis, a new formula for calculating the maximum depth of the scour hole at a dike head is proposed. These research results will be beneficial to the reliability of spur dikes and the sustainability of navigation channels. [ABSTRACT FROM AUTHOR]

The Nile River is the main route for inland navigation in Egypt. The vessels navigating through inland waterways generate complex physical forces that need to be studied extensively. Quantifying the effects of vessels sailing along a waterway is a complex problem because the river flow is unsteady and the river bathymetry is irregular. This paper aims to investigate the hydrodynamic effects resulting from the movement of vessels such as return currents around the vessel, the draw down of the water surface, under keel clearance, and the shear stress induced by vessels operating in the Nile River. Modeling such effects has been performed by applied the two-dimensional ADH (adaptive hydraulics) model to a river reach for different navigation channel operation scenarios. The obtained results show that the draw down heights, the water fluctuation, and the shear stress magnitude are larger when the river cross sectionals are narrow and the shallow water depths. These river sections are considered more disposed to bed erosion and it is morphologically unsafe. The section having the narrowest width and the lowest depth was associated with the largest drawdown percentages of 98.3% and 87.3% in one-way and two-way scenarios. While the section having the widest width and the largest depth was associated with the least drawdown percentages of 48.5% and 51.9% in one-way and two-way scenarios. The section having the narrowest width and the lowest depth was associated with the largest fluctuations of 22.0 cm and 41.9 cm in one-way and two-way scenarios. While the section having the widest width and the largest depth was associated with the least fluctuations of 0.6 cm and 1.8 cm in one-way and two-way scenarios. The section having the narrowest width and the lowest depth was the worst section for under keel clearance of 5.0 cm and 33.3 cm in one-way and two-way scenarios. While the section having the widest width and the largest depth was the best section, where its clearance values were 183.2 cm and 155.0 cm in one-way and two-way scenarios. It is concluded that a numerical model is a valuable tool for predicting and quantifying the hydrodynamic effects of vessels moving through a two-dimensional flow field and can be used to evaluate different scenarios that are difficult to measure in the field or a physical model. Also, it provides visualization products that help us understand the complicated forces produced by vessels moving in a navigation channel. [ABSTRACT FROM AUTHOR]

Copyright of China Sciencepaper is the property of China Sciencepaper and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The article presents a systematic approach to design of marine navigation channels parameters resulting from manoeuvring and operational safety. Relations between the parameters of waterway system elements and the conditions of safe ship operation have been determined and the objective function of waterway parameters' optimization problems has been minimized with respect to variables of construction and operation costs. These costs have been functionally associated to variables of channel width at the bottom and fairway depth. The method of fairway's width computation at specified safe depth at the preliminary and detailed stages of waterway design has been proposed. The results of this method application have been illustrated with two examples: 1. The modernization of Szczecin-Świnoujście fairway aimed at accepting vessels of 60,000 DWT capacity. 2. Construction of an approach channel leading to a newly built container terminal in Świnoujście harbour (Poland), handling ocean-going container ships of 20,000 TEU capacity.

This article presents the use of a computer application codenamed "NEPTUN" to ascertain the waterway parameters of the modernised Świnoujście–Szczecin waterway. The designed program calculates the individual risks in selected sections of the fairway depending on the input data, including the parameters of the ship, available water area, and positioning methods. The collected data used for analyses in individual modules are stored in a SQL server of shared access. Vector electronic navigation charts of S-57 standard specification are used as the cartographic background. The width of the waterway is calculated by means of the method developed on the basis of the modified PIANC guidelines. The main goal of the research is to prove and demonstrate that the designed software would directly increase the navigation safety level of the Świnoujście–Szczecin fairway and indicate the optimal positioning methods in various navigation circumstances. [ABSTRACT FROM AUTHOR]

The refractive effect of the reflection of waves from a channel has made it possible to propose a model of refractive filtering of the frequency-directed wave spectrum by the navigation channel. If the frequency-directed spectrum is known on the way to the channel, then when traversing the channel some frequency components of the waves are reflected from the channel. Thus, part of the wave energy is reflected from the channel; that is, the part of the energy of the initial wave does not reach the second embankment shoulder, which results in a decrease of wave altitude in the region beyond the channel. [ABSTRACT FROM AUTHOR]

This article presents the use of a computer application codenamed “NEPTUN” to ascertain the waterway parameters of the modernised Świnoujście–Szczecin waterway. The designed program calculates the individual risks in selected sections of the fairway depending on the input data, including the parameters of the ship, available water area, and positioning methods. The collected data used for analyses in individual modules are stored in a SQL server of shared access. Vector electronic navigation charts of S-57 standard specification are used as the cartographic background. The width of the waterway is calculated by means of the method developed on the basis of the modified PIANC guidelines. The main goal of the research is to prove and demonstrate that the designed software would directly increase the navigation safety level of the Świnoujście–Szczecin fairway and indicate the optimal positioning methods in various navigation circumstances.

The ARTEMIS model is used to numerically analyze the wave conditions near the Sabetta-Utrenniy port of different layouts. Monochromatic and spectral waves were considered. The results show that a navigation channel can not only cause strong focusing of wave energy, but also give rise to zones of reduced waves. It is important to recognize these effects and use them to optimize the project. [ABSTRACT FROM AUTHOR]

ABSTRACT Ji, Z.Z.; You, Z.J.; Hou, Z.Q., and Wei, Y., 2018. Development of generalized model for estimation of sediment siltation in coastal waterways of China. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 1221–1225. Coconut Creek (Florida), ISSN 0749-0208. Coastal sediment siltation has long been a major problem for design and construction of coastal large-scale ports in the world. Silty sediment siltation often occurs in coastal waterways of China especially during storm events, in which silty sediment is stirred up from the seabed and re-suspended into the water column by storm-induced waves, and transported into the waterways by currents in three forms of suspended load, bedload and sheet-flow load. This study is to derive a generalized model for estimation of sediment siltation rates under both non-storm and storm conditions based on 6-year field data collected in the outer navigation channel of Huanghua Harbor. The sediment siltation data were collected by directly measuring the seabed elevation changes along the port navigation channel from 2002 to 2007. In analyzing the field data collected, a semi-empirical model between effective wind energy and sediment siltation rate is also presented, and found that the newly derived model yields satisfactory agreement with the siltation data collected during the coastal storm events. [ABSTRACT FROM AUTHOR]

South Louisiana is undergoing rapid land loss and the construction and utilization of navigation channels by the offshore oil and gas industry, the commercial fishing industry, the oil refining industry, and freight shippers is one cause. A network of natural and man-made navigation channels support commerce and industry throughout the region, but no quantitative information is available on the users of the channels and their contribution to land loss. The purpose of this note is to characterize utilization across eight channels in South Louisiana using data from the Automatic Identification System. Approximately 125,000 vessels used the channels over a two year period between 2011-2012. The Mississippi River was the most heavily utilized channel with an average of 345 vessels per week across the report zone, followed by Bayou Lafourche and Sabine Pass with about 195 vessels per week. The oil refining industry was the primary user of the Calcasieu and Sabine Pass channels while the freight industry was the primary user of the Mississippi River. The offshore oil and gas industry were the primary users of Bayou Lafourche, the Houma Navigation Canal, the Atchafalaya River and Freshwater Bayou.

Abstract: The High Aswan Dam is one of the largest dams in the world. Completion of the dam in 1970 resulted in the formation of Lake Nasser/Nubia (LNN). LNN has a highly irregular shape and dimensions. Its total length is about 500 km (335 km in Egypt, known as Lake Nasser; 165 km in Sudan, known as Lake Nubia). It has an average width of 12 km, an average depth of about 25 m and a maximum depth of 90 m. Large quantities of sediment are deposited in the lake, which complicates accurate knowledge of its navigational routes. Moreover, the sediment deposition and lowering of water levels has resulted in the creation of shallow areas that navigation bottlenecks. Furthermore, this problem is expected to increase in the future because of climate change impacts, and the effects of upper Nile River projects. The objective of this study was to identify a sustainable channel for navigation purposes in Lake Nasser/Nubia. A numerical model (Delft‐3D) was used to simulate the navigation waterway along Lake Nasser/Nubia. Calibration and verification of the model for flow and sediment deposition were performed during the period of 2009–2012. There was a good agreement between the observed and modelled results for the whole domain. The model was used to evaluate the designed navigation waterway, based on different scenarios. The calculated volume of the needed dredging, based on time series for the years 2002–2006 (‘which represents a minimum flood’), was 5.94 million m3 (mcm); the calculated volume of the dredging using time series for the years 1992–1996 (‘which represents an average flood’) was 6.64 mcm; and the calculated volume of the dredging using time series for the years 1996–2000 (‘which represents a maximum flood’) was 8.46 mcm. The modelling approach proved to be a useful tool for monitoring the future navigation waterway in Lake Nasser/Nubia. [ABSTRACT FROM AUTHOR]

Despite relevant advances in the study of inlet morphodynamics during the last decades, there is still a lack of knowledge regarding the effects of dredging interventions into these systems and their role into the mid-term stability. In this work the case of Punta Umbría, a deeply human-altered inlet in Southwestern Spain, was studied. To ensure the operational capacity and safe navigation throughout the inlet, five dredging works have been done since 2002, according to three alternative navigation channels designs. Given the siltation of the dredged channels and their associated high economic and environmental impacts, regional managers are demanding a more efficient alternative in time with a longer life cycle. The objective of this study is to relate the observed morphological activity to the forcings' dynamics to quantitatively assess the morphodynamic response of the tidal inlet. To this purpose, 18 high–resolution bathymetries of the inlet were analyzed in order to compute the morphological activity of the bed. The Delft3D numerical model was implemented to reproduce the total energy flux, obtained as the sum of both tidal and wave energy fluxes. The model was then calibrated and validated with hydrodynamic measurements from a monitoring network. Results show that the spatial divergence of the total energy flux explains the observed morphological activity patterns in the inlet, where locations with larger sedimentation correspond to those with higher convergence in the total energy flux. Through the reduction of the bed slope a more efficient design was obtained, since it minimizes the divergence of the energy fluxes and hence the bed activity, in contrast to former channel designs. This methodology can be extended to other systems, and therefore improve the efficiency in time of dredging interventions in tidal inlets. [ABSTRACT FROM AUTHOR]

Ports are often located in naturally sheltered areas such as estuaries. The strong tidal currents that occur in many of these areas drive a dynamic morphodynamic regime, with the result that the approach channels to these ports are gradually infilled. Periodic dredging is therefore necessary to maintain the operativity of the port. A case in point is Ribadeo (NW Spain), an important port for the economy of the area. In this work, the sediment transport patterns of the estuary (Ria de Ribadeo) are investigated through high-resolution numerical modelling and field measurements covering a 4-year period. On this basis, a decision-aid tool is developed that enables to predict the time evolution of the approach channel and thus contributes to the planning of dredging operations and, more generally, the maintenance of adequate operativity levels in a cost-effective way. [ABSTRACT FROM AUTHOR]

The Dinh An Estuary is one of the Nine Dragon estuaries of the Mekong River. An international navigation channel was built in the estuary for vessels traveling from the South China Sea to the southwestern area of Vietnam and then to Phnom Penh, Cambodia. The morphological evolution of the navigation channel is complicated and unstable. The back siltation intensity in the navigation channel has largely increased and been concentrated in the curvature segments of the channel since 1980. In this study, based on simulation results and measured data, five key factors that influence the back siltation in the navigation channel were systematically analyzed. These factors included the increasing elevation gap between the channel and the nearby seabed, the disadvantageous hydrodynamic conditions, sediment transport, mixing of saltwater and freshwater, and wave effects in the navigation channel. It is shown that the back siltation to a large extent results from the low current velocity of the secondary ocean circulation, which often occurs in the curvature segments of the channel. Suspended sediment also settles in the channel due to the decrease of the current velocity and the sediment transport capacity when flow passes through the channel. The changes of hydrodynamic conditions are responsible for the majority of the severe siltation in the curvature segments of the navigation channel.

Subject: approach navigation channels and waterbody of port’s area. Many of the new ports require construction of long and deep navigation channels through shallow water to ensure the approach to the berths of large-capacity vessels. Deep channels can have a significant effect on wave propagation, and it is important to consider this interaction at early stages of design to adequately assess the effects of wave action on the waters of the port. Research objectives: studying the influence of approach shipping channels on wave regime of port’s water area. Materials and methods: the work is performed based on observations and published sources, the method of theoretical study, analysis and generalization of the material. Results: refraction and reflection of waves at the edges of the channel can potentially lead to a significant concentration of energy of waves, and also to a generation of areas of reduced wave action. Conclusions: this work has provided examples which demonstrate that the location of navigation channels significantly affects the wave regime in waterbody of the port’s area.

Tam Quan estuary in the Binh Dinh Province of Vietnam provides shelter for about 2000 boats. Recently, erosion and accretion associated with the mouth of the estuary have badly affected marine transportation and economic development. An 850-m-long jetty was constructed to mitigate the hazard. However, sand deposition still continues to be an ongoing problem. This paper aimed to assess the reasons for sand deposition in the estuary based on sediment distributions and transport pathways. Following an investigation of topography, geological and hydrodynamic conditions, and sediment characteristics, an analysis of sediment transport trends was undertaken. Results show that medium sand is distributed along the coast from the shoreline to 2.5 m water depth. Fine sands are found in deeper areas of 10-13 m where there are also medium sand deposits thought to be of ancient origin. Sand deposition has intensively occurred in the estuary due to a dominant north-to-south longshore sediment transport regime. Sediment from this regime is presently trapped by the jetty and deposited in the navigation channel. As a solution, it is suggested that a properly designed jetty stemming from the headland on the north side of the estuary could effectively control the patterns of sediment transport enabling the sand to bypass the entrance, thereby avoiding entrapment inside its mouth. [ABSTRACT FROM AUTHOR]

Copyright of Caldasia is the property of Universidad Nacional de Colombia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)