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Utso, M.; Zaitseva-Pärnaste, I., and Parnell, K.E., 2024. Channel maintenance planning in Estonia. In: Phillips, M.R.; Al-Naemi, S., and Duarte, C.M. (eds.), Coastlines under Global Change: Proceedings from the International Coastal Symposium (ICS) 2024 (Doha, Qatar). Journal of Coastal Research, Special Issue No. 113, pp. 95-99. Charlotte (North Carolina), ISSN 0749-0208. This paper addresses the critical issue of maintaining navigational channels in Estonia, where challenges due to insufficient depth necessitate frequent dredging. Given Estonia's reliance on maritime transport for connectivity and trade, ensuring safe navigation amid evolving environmental conditions is imperative. The study aims to comprehensively analyze maintenance practices for navigational channels, focusing on the critical Rukki channel between the mainland and the island of Hiiumaa. Historical data gaps hinder understanding, while fragmented management worsens the problem. The study employs various methods, to shed light on channel maintenance complexities and advocate for standardized guidelines and improved documentation. This study aims to clarify the processes of channel infill and dredging in the channel of Rukki and facilitate better planning of future works.

Sediment deposition in the north passage of the Changjiang Estuary, where the Deep-water Navigation Channel (DNC) is located, has been a major concern in the past decades. To understand the suspended sediment dynamics and the effects of sediment-induced stratification on sediment flux in the navigational channel, field data on tidal flow and suspended sediment concentration (SSC) are collected and analyzed in this study. It is shown that net sediment transport is dominated by ebb currents in the study area. The net sediment flux is generally toward the ocean and the maximum value is found to be in the middle reach of the passage. In the lower reach of the passage, the net sediment flux is landward in the lower layer and seaward in the upper layer of the water column due to the two-layer feature of the estuarine circulation. Advective flux plays a significant role in transport of sediment in upper and middle reaches of the passage by carrying 70–100% of the suspended sediment. However, this amount is reduced to 30–60% in lower reach of the passage, where tidal effects become more important. The suspended sediment-induced stratification in the north passage is examined by calculating eddy viscosity. It is found that suspended sediment can reduce eddy viscosity by 10–30%. The highest depth-averaged SSC is located in the middle reach of the north passage, where the averaged SSC is 4–15 times higher than that in the upper reach. In this region, bed shear stress is larger at ebb, while SSC is higher at flood. It is inferred that suspended sediments in the DNC during flood are partially transported from a neighboring shoal, which plays an important role in sediment dynamics in the north passage.

Reef passes are deep, navigable channels dissecting coral reefs around volcanic islands. Many reef passes are located offshore of large island river basins, suggesting a potential causal relationship. To clarify the mechanisms that form and maintain reef passes, we quantify the relationships between reef pass location and drainage basin size in the Society Islands. River basins draining toward reef passes are larger than those draining toward unbroken reef flats, suggesting that rivers help create and sustain reef passes. The correlation between reef passes and large rivers weakens for older islands, suggesting that oceanographic processes increasingly maintain passes as islands age and subside. We propose two river‐driven reef pass formation mechanisms: reef incision, in which rivers erode into reefs during sea‐level lowstands, and reef encroachment, in which corals growing in lower‐elevation submerged river valleys preferentially drown during periods of rapid sea‐level rise, leaving gaps in the accreting reef. Plain Language Summary Coral reefs ring many volcanic ocean islands in the Pacific Ocean. It is well known that rivers discharging freshwater and sediment off islands affect reef structure and composition. Reef passes, or deep channels through reefs surrounding ocean islands, may result from long‐term river erosion. Previous studies have proposed that reef passes correspond to the outlets of large island rivers, but this hypothesis has not been tested statistically. Here, we investigate if reef passes are close to big drainage basins through a geospatial analysis of the Society Islands Archipelago. We find that larger river basins on the islands drain to parts of the reef where passes are found, suggesting that river erosion plays a vital role in determining where deep channels are located within reefs, particularly for younger volcanic islands. We propose two ideas for how rivers could create passes in the Society Islands: reef incision, where rivers directly cut passes into reefs exposed when sea level is lower, and reef encroachment, where old river channels on land are preserved as passes when sea level rises. Our results show how rivers may support reef health over geologic timescales by enhancing water circulation between lagoons and oceans. Key Points Reef pass location is significantly correlated with island drainage basin size in the Society Islands Archipelago Relationships between large rivers and reef passes weaken as islands age, implying that ocean processes maintain passes at older islands We propose two mechanisms through which rivers may form and maintain reef passes through sea‐level cycles

National Company Administration of the Navigable Channels provides to users the shipping infrastructure belonging to tiie domain public of state, in accordance with the legislation in force. The main advantage of the Danube Black Sea Channel is the direct link with Constanta port. The Danube-Black Sea Channel connects the Black Sea with several countries from Central Europe, such as Austria, Hungary, the Czech Republic and Slovakia. The paper presents the evolution of snip traffic on the channel and the Russo-Ukrainian war influence on goods traffic. Keywords (3-5): navigable channels, Danube - Black Sea Channel, traffic, war influence.

Salt mixing enables the transport of water between the inflow and outflow layers of estuarine circulation and therefore closes the circulation by driving a diahaline exchange flow. A recently derived universal law links the salt mixing inside an estuarine volume bounded by an isohaline surface to freshwater discharge: it states that on long-term average, the area-integrated mixing across the bounding isohaline is directly proportional to the freshwater discharge entering the estuary. However, even though numerous studies predict that periods of extreme discharge will become more frequent with climate change, the direct impact of such periods on estuarine mixing and circulation has yet to be investigated. Therefore, this numerical modeling study focuses on salinity mixing and diahaline exchange flows during a low-discharge and an extreme high-discharge period. To this end, we apply a realistic numerical setup of the Elbe estuary in northern Germany, using curvilinear coordinates that follow the navigational channel. This is the first time the direct relationship between diahaline exchange flow and salt mixing as well as the spatial distribution of the diahaline exchange flow is shown in a realistic tidal setup. The spatial distribution is highly correlated with the local mixing gradient for salinity, such that inflow occurs near the bottom at the upstream end of the isohaline. Meanwhile, outflow occurs near the surface at its downstream end. Last, increased vertical stratification occurs within the estuary during the high-discharge period, while estuarine-wide mixing strongly converges to the universal law for averaging periods of the discharge event time scale.

Navigational channels and approaches to ports may have bends that constitute the specific sailing conditions for ships. A vessel’s entrance into a bend and its safe passing depends on the ship’s position accuracy, turn angle, and internal and external forces influencing the ships, as well as the captain’s or pilot’s experience. In order to assure a ship’s safe navigation under specific conditions, the possibility to measure individual ship movement parameters with the use of special sensors is needed to accurately calculate the ship’s trajectory considering the specific dimensions of ships. Moreover, hydro-meteorological and hydrological limitations for ships with different parameters and maneuverability should be evaluated in advance. The article aims to develop the methodology for calculating ships’ route trajectory in channel bends and approaches to ports under special navigational conditions. The mathematical model that may be used to calculate wind velocity limitations and distance crossed by a ship during maneuvers, depending on the ship’s maneuverability, hydro-metrological, and hydrological conditions, was elaborated. The methodology was verified by the example of a few ships entering specific channel bends. Wind velocity limitations depending on wind direction for the SUEZMAX tanker and other selected types of ships during crossing navigational channel bend near Klaipeda port were calculated. The presented theoretical basis may be used by ships’ captains and pilots who plan and perform operations of vessels’ crossing the approaches to ports and navigational channel bends, as well as by navigational channels designers who plan the channel’s parameters in difficult geographical and navigational conditions. Its application may influence the safety increase of maritime transport in limited or specific areas.

Deepening of estuarine channels is a common practice to ensure navigation. Here, we investigate whether such deepening impacts physical processes such as the strength of the estuarine exchange flow, the horizontal salinity gradient, and tidal dynamics. We analyze recent and historical hydrodynamic observations in Newark Bay, New Jersey, to assess the effect of channel deepening on tides, circulation, and salinity. The Bay's navigational channel has undergone significant deepening, from 3 to 10 m in the nineteenth century to ~16 m today. Observations presented here include sea-level data from the nineteenth, twentieth, and twenty-first century, and moored Doppler current data and bottom salinity measurements made over the past 20 years. Results show a doubling of the estuarine exchange flow, a slight increase in salinity and in the horizontal salinity gradient, a decrease in tidal current amplitude, and a spatially variable change in the tidal range. The doubling of the exchange flow is consistent with the Hansen and Rattray scaling provided that the horizontal salinity gradient is unable to fully adjust landward because the dredging is limited to a short reach of the estuary. However, uncertainty in channel depth leaves open the possibility that the exchange flow is also augmented by an increase in the horizontal salinity gradient and/or a reduction in vertical mixing. Nevertheless, results demonstrate that a relatively small (15%) increase in depth appears to have doubled the exchange flow. We believe that this result is relevant to other systems where dredging is limited to a short reach of an estuary.

To materialize the inherent opportunities of incoming sediment load, various interventions are being practiced for sediment management in rivers and delta systems. Broadly, the practiced methods can be divided into two categories: (i) management for accelerating siltation to enhance land reclamation and counterbalancing bank erosion (ii) management for de-siltation in the channels to maintain required navigational flow depth. The prerequisites for achieving the above targets at the same time are quite contradictory, as land reclamation requires more sediment, while maintaining navigational depth requires less sediment load. To address the aforementioned constraints, Bandal-like Structures (BLS), an indigenous nature-based solution, has proposed for redistributing the local flow-sediment regime to create a sediment deficit zone within the river side and a sediment surplus zone along the bankside, which can eventually be useful for the maintenance of navigational channels as well as bank stabilization. Based on research conducted over the last 20 years, this article discusses BLS's experiences in achieving both functions simultaneously. A well-documented case study of its application along a reach of the braided Jamuna River is one of many implemented BLS at various scales in the Ganges-Jamuna-Brahmaputra (GBM) system. Based on the performance of the implemented case study and existing indigenous knowledge, a hybrid approach integrating conventional and community sciences is proposed as a nature-based solution for sustainable sediment management in Bangladesh's river systems.

This study investigates the sensitivity of the Calcasieu Lake estuarine region to channel deepening in southwest Louisiana in the USA. We test the hypothesis that the depth increase in a navigational channel in an estuarine region results in the amplification of the inland penetration of storm surge, thereby increasing the flood vulnerability of the region. We run numerical experiments using the Delft3D modeling suite (validated with observational data) with different historic channel depth scenarios. Model results show that channel deepening facilitates increased water movement into the lake–estuary system during a storm surge event. The inland peak water level increases by 37% in the presence of the deepest channel. Moreover, the peak volumetric flow rate increases by 291.6% along the navigational channel. Furthermore, the tidal prism and the volume of surge prism passing through the channel inlet increase by 487% and 153.3%, respectively. In our study, the presence of the deepest channel results in extra 56.72 km2 of flooded area (approximately 12% increase) which is an indication that channel deepening over the years has rendered the region more vulnerable to hurricane-induced flooding. The study also analyzes the impact of channel deepening on storm surge in estuaries under different future sea-level rise (SLR) scenarios. Simulations suggest that even the most conservative scenario of SLR will cause an approximately 51% increase in flooded area in the presence of the deepest ship channel, thereby suggesting that rising sea level will cause increased surge penetration and increased flood risk.

Overtaking situations are commonly encountered in maritime navigation, and the overtaking process involves various risk factors that significantly contribute to collision incidents. It is crucial to conduct research on the maneuvering behaviors and decision-making processes associated with ship overtaking. This paper proposes a method based on the analysis of ship maneuvering performance to investigate overtaking behaviors in navigational channels. A relative motion model is established for both the overtaking and the overtaken vessels, and the inter-vessel distance is calculated, taking into account the psychological perceptions of the ship’s driver. A decision-making model for ship overtaking is presented to provide a safety protocol for overtaking maneuvers. Applying this method to overtaking data from the South Channel shows that it effectively characterizes both the permissible overtaking space and the driver’s overtaking desire. Additionally, it enables the prediction of optimal overtaking timing and strategies based on short-term trajectory forecasts. Thus, this method not only offers a safe overtaking plan for vessels but also provides auxiliary information for decision making in intelligent ship navigation.