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21 pages, 18532 KiB

Open AccessArticle

Cesium-137 Distribution Patterns in Bottom Sediments of Beaver Ponds in Small Rivers in the North of the Volga Upland, European Russia

by Artyom V. Gusarov, Aidar G. Sharifullin, Achim A. Beylich and Fedor N. Lisetskii

Water 2025, 17(4), 503; https://doi.org/10.3390/w17040503 - 11 Feb 2025

Viewed by 716

Abstract

This paper presents the results of the analysis of the redistribution of cesium-137 (¹³⁷Cs) in the bottom sediments of beaver ponds in two small rivers in the forest-steppe north of the Volga Upland, which is one of the most contaminated areas [...] Read more.

This paper presents the results of the analysis of the redistribution of cesium-137 (¹³⁷Cs) in the bottom sediments of beaver ponds in two small rivers in the forest-steppe north of the Volga Upland, which is one of the most contaminated areas of the Middle Volga region (European Russia) with artificial radionuclides. This study is based on fieldwork materials, laboratory analyses of the specific radioactivity of ¹³⁷Cs in soil and bottom sediment samples, their granulometric composition, and the content of organic matter in them. The obtained results indicate a significant decrease in the specific activity of ¹³⁷Cs in the direction from near-water-divide surface soils (on average, 54 Bq/kg) to the bottom sediments of beaver ponds of the studied rivers (on average, no more than 6 Bq/kg). A weak (statistically insignificant) tendency towards a decrease in the specific activity of ¹³⁷Cs in the bottom sediments of beaver ponds downstream of rivers was also revealed. With this detected trend, no statistically significant relationship was found between changes in ¹³⁷Cs and changes in the granulometric composition of bottom sediments. However, a relatively good relationship was identified with changes in the content of total organic matter. The stage-by-stage accumulation of sediment thickness in one of the beaver ponds was revealed, with the highest concentration of ¹³⁷Cs in the layer with the highest content of finely dispersed fractions and organic matter. The obtained results indicate that for a correct quantitative assessment of the migration of pollutants (including radioactive ones) in floodplain-channel systems, it is necessary to consider beaver structures (primarily ponds), which act as zones of their intensive accumulation. Full article

(This article belongs to the Special Issue Hydrodynamics and Sediment Transport in the Coastal Zone)

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21 pages, 4180 KiB

Open AccessArticle

Influence of Vertical Force on Shields’ Curve and Its Extension in Rapidly Varied Flow

by Muhammad Zain Bin Riaz, Umair Iqbal, Huda Zain, Shu-Qing Yang, Muttucumaru Sivakumar, Rong Ji and Muhammad Naveed Anjum

Water 2024, 16(20), 2960; https://doi.org/10.3390/w16202960 - 17 Oct 2024

Viewed by 986

Abstract

Sediment transport is a geophysical phenomenon characterized by the displacement of sediment particles in both the horizontal and vertical directions due to various forces. Most of the sediment transport equations currently used include only parameters related to the horizontal direction. This study measured [...] Read more.

Sediment transport is a geophysical phenomenon characterized by the displacement of sediment particles in both the horizontal and vertical directions due to various forces. Most of the sediment transport equations currently used include only parameters related to the horizontal direction. This study measured both instantaneous longitudinal and vertical parameters, i.e., velocities and forces, and found that the magnitude and direction of the vertical force play an important role in sediment incipient motion. An innovative experimental system was developed to investigate the effect of vertical force on incipient motion in rapidly varying flows. A quadrant analysis of the instantaneous measured forces on the critical shear stress was performed. The research revealed that upward positive vertical forces enhance particle mobility, whereas downward negative vertical forces increase particle stability. Novel equations have been developed to represent the influence of vertical forces on sediment transport. A comprehensive critical Shields stress for sediment transport was proposed, extending the Classic Shields diagram to encompass the incipient motion in highly unsteady flows. Full article

(This article belongs to the Special Issue Hydrodynamics and Sediment Transport in the Coastal Zone)

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24 pages, 12144 KiB

Open AccessArticle

Numerical Investigation of the Sediment Load Exchange between a Coastal Mud Bank and Its Neighbouring Estuary

by Noelia Abascal-Zorrilla, Nicolas Huybrechts, Sylvain Orseau, Vincent Vantrepotte, Edward Anthony and Antoine Gardel

Water 2024, 16(20), 2885; https://doi.org/10.3390/w16202885 - 11 Oct 2024

Viewed by 1030

Abstract

Muddy coastlines cover much of the world’s shores, yet studies on the interaction between mud-affected coasts and estuaries are limited. This study focuses on the Mahury River estuary and its interaction with the muddy coast of the Guianas, primarily fed by the Amazon. [...] Read more.

Muddy coastlines cover much of the world’s shores, yet studies on the interaction between mud-affected coasts and estuaries are limited. This study focuses on the Mahury River estuary and its interaction with the muddy coast of the Guianas, primarily fed by the Amazon. A coupled wave–current–sediment transport model is developed to analyze the sediment exchange in an environment with strong interactions between the waves and the fluid mud. Simulations explore how seasonal changes in waves, mud availability, and tides affect sediment fluxes. The main processes influencing suspended particulate matter (SPM) and sediment transport are well emulated, notwithstanding the complexity of the ambient muddy environment. The results show that during the rainy season, strong wave damping and wave refraction zones cause high SPM resuspension in shallow waters (<5 m). In contrast, during the dry season, wave influence shifts to the estuary mouth. Erosion and sedimentation patterns indicate that ebb currents associated with neap tides during the rainy season represent the most favourable conditions for the alongshore migration of mud banks. Neaptide ebb currents also contribute to sedimentation during the dry season but only in the estuary mouth and the nearby coastal area. The abundance of mud leads to an extension of the estuary’s intertidal area during the dry season. Full article

(This article belongs to the Special Issue Hydrodynamics and Sediment Transport in the Coastal Zone)

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24 pages, 14077 KiB

Open AccessArticle

Spatio-Temporal Variation in Suspended Sediment during Typhoon Ampil under Wave–Current Interactions in the Yangtze River Estuary

by Jie Wang, Cuiping Kuang, Daidu Fan, Wei Xing, Rufu Qin and Qingping Zou

Water 2024, 16(13), 1783; https://doi.org/10.3390/w16131783 - 24 Jun 2024

Cited by 1 | Viewed by 1697

Abstract

Suspended sediment plays a major role in estuary morphological change and shoal erosion and deposition. The impact of storm waves on sediment transport and resuspension in the Yangtze River Estuary (YRE) was investigated using a 3D coupling hydrodynamic-wave model with a sediment transport [...] Read more.

Suspended sediment plays a major role in estuary morphological change and shoal erosion and deposition. The impact of storm waves on sediment transport and resuspension in the Yangtze River Estuary (YRE) was investigated using a 3D coupling hydrodynamic-wave model with a sediment transport model during Typhoon Ampil. This model has been validated in field observations of water level, current, wave, and sediment concentration. The model was run for tide only, tide + wind, tide + wind and wave forcing conditions. It was found that: (1) typhoons can increase the suspended sediment concentration (SSC) by enhancing bed shear stress (BSS), especially in the offshore area of the YRE, and there is hysteresis between SSC and BSS variation; (2) exponential and vertical-line types are the main vertical profile of the SSC in the YRE and typhoons can strengthen vertical mixing and reconstruct the vertical distribution; and (3) waves are the dominating forcing factor for the SSC in the majority of the YRE through wave-induced BSS which releases sediment from the seabed. This study comprehensively investigates the spatio-temporal variation in SSC induced by Typhoon Ampil in the main branch of the YRE, which provides insights into sediment transport and resuspension during severe storms for estuaries around the world. Full article

(This article belongs to the Special Issue Hydrodynamics and Sediment Transport in the Coastal Zone)

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17 pages, 8206 KiB

Open AccessArticle

A Multi-Approach Analysis for Monitoring Wave Energy Driven by Coastal Extremes

by Reine Matar, Nizar Abcha, Iskander Abroug, Nicolas Lecoq and Emma-Imen Turki

Water 2024, 16(8), 1145; https://doi.org/10.3390/w16081145 - 18 Apr 2024

Cited by 2 | Viewed by 2305

Abstract

This research investigates the behavior and frequency evolution of extreme waves in coastal areas through a combination of physical modeling, spectral analysis, and artificial intelligence (AI) techniques. Laboratory experiments were conducted in a wave flume, deploying various wave spectra, including JONSWAP (γ = [...] Read more.

This research investigates the behavior and frequency evolution of extreme waves in coastal areas through a combination of physical modeling, spectral analysis, and artificial intelligence (AI) techniques. Laboratory experiments were conducted in a wave flume, deploying various wave spectra, including JONSWAP (γ = 7), JONSWAP (γ = 3.3), and Pierson–Moskowitz, using the dispersive focusing technique, covering a broad range of wave amplitudes. Wave characteristics were monitored using fifty-one gauges at distances between 4 m and 14 m from the wave generator, employing power spectral density (PSD) analysis to investigate wave energy subtleties. A spectral approach of discrete wavelets identified frequency components. The energy of the dominant frequency components, d5 and d4, representing the peak frequency (f_p = 0.75 Hz) and its first harmonic (2f_p = 1.5 Hz), respectively, exhibited a significant decrease in energy, while others increased, revealing potential correlations with zones of higher energy dissipation. This study underscores the repeatable and precise nature of results, demonstrating the Multilayer Perceptron (MLP) machine learning algorithm’s accuracy in predicting the energy of frequency components. The finding emphasizes the importance of a multi-approach analysis for effectively monitoring energy in extreme coastal waves. Full article

(This article belongs to the Special Issue Hydrodynamics and Sediment Transport in the Coastal Zone)

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29 pages, 31346 KiB

Open AccessArticle

Monitoring Sediment Transport in Certain Harbor Launches in the Southeastern Black Sea

by Servet Karasu, Hasan Oğulcan Marangoz, Barbaros Hayrettin Kocapir, Enver Yilmaz, İsmail Hakkı Özölçer and Adem Akpinar

Water 2023, 15(21), 3860; https://doi.org/10.3390/w15213860 - 6 Nov 2023

Cited by 1 | Viewed by 1917

Abstract

The problem of shoaling on coastal structures is the result of an event that occurs as part of the natural cycle. In cases where shoaling cannot be detected or prevented, various economic and operational problems may arise and may cause disruptions. In this [...] Read more.

The problem of shoaling on coastal structures is the result of an event that occurs as part of the natural cycle. In cases where shoaling cannot be detected or prevented, various economic and operational problems may arise and may cause disruptions. In this study, the complex coastal dynamic impact of shoaling on three sequential fishery coastal structures located within the borders of Rize province in the Eastern Black Sea region of Türkiye was examined in terms of bathymetric changes and sediment transport under the influence of the incident wave climate. The effects of these structures on each other were also investigated. With this aim, bathymetric measurements were carried out to examine the impact of waves on seabed erosion and deposition. A serious shoaling problem was identified at one of the harbor launches under investigation, where approximately 13,200 m³ of deposition occurs annually in a relatively small harbor launch area. Such physical problems are thought to be the result of shoaling, the selection of sites that are not viable for fishery-related coastal structures, or the wrong positioning of the breakwater. Full article

(This article belongs to the Special Issue Hydrodynamics and Sediment Transport in the Coastal Zone)

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Graphical abstract

23 pages, 9852 KiB

Open AccessArticle

A Study on the Characteristics of Beach Profile Evolution According to the Particle Size Variation of Beach Nourishment

by Kyu-Tae Shim and Kyu-Han Kim

Water 2023, 15(16), 2956; https://doi.org/10.3390/w15162956 - 16 Aug 2023

Cited by 1 | Viewed by 2822

Abstract

This study investigated the beach nourishment effect and topographical changes when using nourishment sand with relatively large particle diameters to perform beach nourishment on a beach subject to erosion. A physical model test was conducted in a 2D wave flume with an installed [...] Read more.

This study investigated the beach nourishment effect and topographical changes when using nourishment sand with relatively large particle diameters to perform beach nourishment on a beach subject to erosion. A physical model test was conducted in a 2D wave flume with an installed wind tunnel. The experiment examined the sediment transport mechanism under conditions with wind and waves. Although applying nourishment sand with large particle diameters attenuated sediment transport, the increase in particle diameter was not always proportional to the reduction in topographical changes. Increasing the particle diameter of the nourishment sand increased the friction force between particles, resulting in large-scale erosion and accretion around the coastline, and this trend increased with winds. Also, with wind, the wave run-up height increased, the undertow became stronger, and large-scale scouring occurred at the boundary between the nourishment sand and the existing beach. Increasing the particle diameter of the nourishment sand played a role in reducing the run-up phenomenon (d₅₀: 1.0 mm with 24–50%, d₅₀: 5.0 mm with 59–83%), and the range of particles moved by winds also decreased (d₅₀: 1.0 mm with 10–38%, d₅₀: 5.0 mm with 5–37%). Full article

(This article belongs to the Special Issue Hydrodynamics and Sediment Transport in the Coastal Zone)

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Review

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13 pages, 308 KiB

Open AccessReview

Cross-Shore Sediment Transport in the Coastal Zone: A Review

by François Marin and Mélanie Vah

Water 2024, 16(7), 957; https://doi.org/10.3390/w16070957 - 26 Mar 2024

Cited by 1 | Viewed by 1969

Abstract

This paper presents a review of cross-shore sediment transport for non-cohesive sediments in the coastal zone. The principles of sediment incipient motion are introduced. Formulations for the estimation of bedload transport are presented, for currents and combined waves and current flows. A method [...] Read more.

This paper presents a review of cross-shore sediment transport for non-cohesive sediments in the coastal zone. The principles of sediment incipient motion are introduced. Formulations for the estimation of bedload transport are presented, for currents and combined waves and current flows. A method to consider the effect of sediment heterogeneity on transport, using the hiding–exposure coefficient and hindrance factor, is depicted. Total transport resulting from bedload and transport by suspension is also addressed. New research is encouraged to fill the knowledge gap on this topic. Full article

(This article belongs to the Special Issue Hydrodynamics and Sediment Transport in the Coastal Zone)

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