Water

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17 pages, 8092 KiB

Open AccessArticle

Climate-Driven Wave Analysis Reveals Changes in Alongshore Sediment Transport: The Case of the Coastal Zone of a Harbor in Thermaikos Bay (NW Aegean Sea)

by Christos Ntafloukas and Yiannis Savvidis

Water 2024, 16(12), 1703; https://doi.org/10.3390/w16121703 - 14 Jun 2024

Viewed by 631

Abstract

The sediment transport along a coastal zone of Thermaikos Bay and the interaction with the coastline were studied in the present research. This study concerns the greater basin of an existing breakwater, for which the sand transport during the time periods 1950–1968 and [...] Read more.

The sediment transport along a coastal zone of Thermaikos Bay and the interaction with the coastline were studied in the present research. This study concerns the greater basin of an existing breakwater, for which the sand transport during the time periods 1950–1968 and 2009–2017, before and after the construction of the breakwater, were examined. The breakwater led to sand accumulation behind it, causing the well-known phenomenon of salient. It was revealed that climate change, in terms of wind conditions, significantly affected sediment transport; more specifically, the sand transport during 2009–2017 not only decreased significantly, but also changed its direction, in relation to 1950–1968. Based on the information obtained, technical interventions are proposed for the interception of sediment transport and the consequent accumulation of sand behind the breakwater. Full article

(This article belongs to the Special Issue Hydrodynamics in Coastal Areas)

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20 pages, 6650 KiB

Open AccessArticle

Seasonal Study of the Kako River Discharge Dynamics into Harima Nada Using a Coupled Atmospheric–Marine Model

by Valentina Pintos Andreoli, Hikari Shimadera, Hiroto Yasuga, Yutaro Koga, Motoharu Suzuki and Akira Kondo

Water 2024, 16(4), 614; https://doi.org/10.3390/w16040614 - 19 Feb 2024

Viewed by 1169

Abstract

This study developed a coupled atmospheric–marine model using the COAWST model system for the Harima Nada area between spring 2010 and winter 2011 to evaluate the seasonal influence of the Kako River’s discharge in the sea. The Kako River is one of the [...] Read more.

This study developed a coupled atmospheric–marine model using the COAWST model system for the Harima Nada area between spring 2010 and winter 2011 to evaluate the seasonal influence of the Kako River’s discharge in the sea. The Kako River is one of the largest rivers in southwest Japan, contributing almost half of the freshwater discharged in the Harima Nada region in the Seto Inland Sea. Validation was conducted for the entire period, showing a good performance for the atmospheric and marine variables selected. Multiple experiments injecting an inert tracer in the Kako River estuary were performed to simulate the seasonal river water distribution from the estuary into the sea and to analyze the seasonal differences in concentration patterns and mean residence times in Harima Nada. Because the study area is shallow, the results were evaluated at the surface and 10 m depth layers and showed significant seasonal differences in tracer distribution, circulation patterns, and mean residence times for the region. On the other hand, differences seemed to not be significant during the same season at different depths. The obtained results also agreed with the area’s natural water circulation, showing that the Kako River waters tend to distribute towards the west coast of Harima Nada in the warmer seasons but shift towards the east in winter. The influence of the Kako River in the center of the study area is seasonal and strongly dependent on the direction of the horizontal velocities more than their magnitude. The mean residence times varied seasonally from approximately 30 days in spring to 12 days in fall. The magnitude of the horizontal velocity was found to be maximum during summer when circulation patterns at the surface and 10 m depth in the central part of Harima Nada also seem to promote the strongest horizontal and vertical mixes. Full article

(This article belongs to the Special Issue Hydrodynamics in Coastal Areas)

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20 pages, 3493 KiB

Open AccessArticle

Size Distribution and Variation in Surface-Suspended Sediments in the North Passage Estuarine Turbidity Maximum of the Yangtze Estuary

by Steve L. Zeh Assam, Yongping Chen, Ao Chu, Samuel Ukpong Okon, Genide Anteilla L. M. and Giresse Ze Eyezo’o

Water 2024, 16(2), 306; https://doi.org/10.3390/w16020306 - 17 Jan 2024

Viewed by 1513

Abstract

One of the most important processes for mass movement in coastal areas is sediment transport; it plays a significant role in coastal morphology changes. This manuscript focuses on the distribution and variation in surface-suspended sediments in the North Passage of the Yangtze Estuary. [...] Read more.

One of the most important processes for mass movement in coastal areas is sediment transport; it plays a significant role in coastal morphology changes. This manuscript focuses on the distribution and variation in surface-suspended sediments in the North Passage of the Yangtze Estuary. Field data on surface-suspended sediment concentration (SSSC) and suspended particle size (SPS) were collected at fifteen hydrological sites over a period of three years, from 2016 to 2018. The main objective was to analyze the spatial and temporal patterns of sediment and particle size and their potential impact on the estuary. Results indicate that extreme weather events have an influence on the hydrological conditions and sediment dynamics of the area. The intensity and range of SSSC variation in the North Passage seem to be determined by the magnitude of the current velocity, while the sediment load significantly impacted the sediment distribution pattern. This study demonstrates that surface sediment dynamics can be used as a basis for understanding the spatiotemporal variation in estuarine turbidity maximum (ETM) in the North Passage of the Yangtze Estuary. Full article

(This article belongs to the Special Issue Hydrodynamics in Coastal Areas)

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19 pages, 4037 KiB

Open AccessArticle

High-Order Boussinesq Equations for Water Wave Propagation in Porous Media

by Ping Wang, Zhongbo Liu, Kezhao Fang, Jiawen Sun and Daxun Gou

Water 2023, 15(22), 3900; https://doi.org/10.3390/w15223900 - 8 Nov 2023

Cited by 1 | Viewed by 1220

Abstract

To accurately capture wave dynamics in porous media, the higher-order Boussinesq-type equations for wave propagation in deep water are derived in this paper. Starting with the Laplace equations combined with the linear and nonlinear resistance force of the dynamic conditions on the free [...] Read more.

To accurately capture wave dynamics in porous media, the higher-order Boussinesq-type equations for wave propagation in deep water are derived in this paper. Starting with the Laplace equations combined with the linear and nonlinear resistance force of the dynamic conditions on the free surface, the governing equations were formulated using various independent velocity variables, such as the depth-averaged velocity and the velocity at the still water level and at an arbitrary vertical position in the water column. The derived equations were then improved, and theoretical analyses were carried out to investigate the linear performances with respect to phase celerity and damping rate. It is shown that Boussinesq-type models with Padé [4, 4] dispersion can be applied in deep water. A numerical implementation for one-dimensional equations expressed with free surface elevation and depth-averaged velocity is presented. Solitary wave propagation in porous media was simulated, and the computed results were found to be generally in good agreement with the measurements. Full article

(This article belongs to the Special Issue Hydrodynamics in Coastal Areas)

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14 pages, 11185 KiB

Open AccessArticle

Water Renewal Simulation in Two Flow-Through Water Bodies in Western Greece

by Nikolaos Th. Fourniotis and Georgios A. Leftheriotis

Water 2023, 15(15), 2745; https://doi.org/10.3390/w15152745 - 29 Jul 2023

Viewed by 1122

Abstract

The basic hydrodynamic characteristics and water renewal of two flow-through water bodies in Western Greece, the Gulf of Patras and Lysimachia Lake, are studied via numerical simulations. The currents on the northern coasts of the Gulf are much stronger compared with the southern [...] Read more.

The basic hydrodynamic characteristics and water renewal of two flow-through water bodies in Western Greece, the Gulf of Patras and Lysimachia Lake, are studied via numerical simulations. The currents on the northern coasts of the Gulf are much stronger compared with the southern region, and rapid water renewal is achieved in the area of the Rio–Antirio strait (<1 month). In the northern part of the Gulf, the residence time varies from 1 to 4 months, while in the central and southern parts, it is estimated to exceed 6 months. Regarding the water renewal of deep waters (>60 m), which are enclosed between sills, the same pattern was observed, with residence times exceeding 6 months. In Lysimachia Lake, the effect of inflow waters from surrounding water bodies was analyzed over a time period of approximately 2 months. Gyres formation was observed due to local topography, and the numerically predicted results for water renewal were found to be in good agreement with those in the literature. Specifically, Lysimachia Lake seems to be replenished approximately 13 times per year. Full article

(This article belongs to the Special Issue Hydrodynamics in Coastal Areas)

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14 pages, 4828 KiB

Open AccessArticle

Abnormal Waves Observation and Analysis of the Mechanism in the Pearl River Estuary, South China

by Hui Shi, Yao Luo, Fenghua Zhou, Chunhua Qiu, Dongxiao Wang and Zhenqiu Zhang

Water 2023, 15(5), 1001; https://doi.org/10.3390/w15051001 - 6 Mar 2023

Viewed by 2023

Abstract

The Pearl River Estuary is a typical estuary region in southern China, and the study of surface wave occurrence and characteristics is of great importance for shipping management, nearshore engineering, and monitoring shoreline changes and other human activities. Long-term and continuous observational data [...] Read more.

The Pearl River Estuary is a typical estuary region in southern China, and the study of surface wave occurrence and characteristics is of great importance for shipping management, nearshore engineering, and monitoring shoreline changes and other human activities. Long-term and continuous observational data are critical for achieving a better understanding of waves. In this study, the wave measurements based on a high-precision wave gauge were analyzed and observation data over approximately two years at a sampling frequency of 2 Hz were obtained. The wave system in the Pearl River Estuary was found to deviate from the assumption of a stationary stochastic process similar to that in the open ocean, due to the effects of abnormal waves caused by human activities. Therefore, traditional distribution functions such as Rayleigh and Weibull were not suitable for accurately fitting the main wave parameters (

H_{s}

,

T_{p}

, etc.), particularly in the tail. Consequently, abnormal wave signals were extracted from all wave sets, and through the comparison and analysis of the wave spectral features, it was determined that these abnormal waves are caused by the ship wakes. The spectral characterization of these waves was performed to determine the characteristics of different ship wake processes. Ship wakes in the Pearl River Estuary are an important part of the wave system, and their wave height is significantly larger than the normal wave. Based on the spectral characteristics of ship wakes, this study proposed some news characteristics of ship wakes in the main channel of the Pearl River Estuary. Full article

(This article belongs to the Special Issue Hydrodynamics in Coastal Areas)

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17 pages, 5629 KiB

Open AccessArticle

Implications of a Large River Discharge on the Dynamics of a Tide-Dominated Amazonian Estuary

by Ariane M. M. Silva, Hannah E. Glover, Mariah E. Josten, Vando J. C. Gomes, Andrea S. Ogston and Nils E. Asp

Water 2023, 15(5), 849; https://doi.org/10.3390/w15050849 - 22 Feb 2023

Cited by 2 | Viewed by 2988

Abstract

Estuaries along the Amazonian coast are subjected to both a macrotidal regime and seasonally high fluvial discharge, both of which generate complex circulation. Furthermore, the Amazon River Plume (ARP) influences coastal circulation and suspended sediment concentrations (SSCs). The Gurupi estuary, located south of [...] Read more.

Estuaries along the Amazonian coast are subjected to both a macrotidal regime and seasonally high fluvial discharge, both of which generate complex circulation. Furthermore, the Amazon River Plume (ARP) influences coastal circulation and suspended sediment concentrations (SSCs). The Gurupi estuary, located south of the mouth of the Amazon River, is relatively unstudied. This study evaluates how the Gurupi estuary dynamics respond to seasonal discharge and the varying influence of the ARP using cross-sectional and longitudinal surveys of morphology, hydrodynamics, and sediment transport. The Gurupi was classified as a tide-dominated estuary based on morphology and mean hydrodynamic conditions. However, the estuary was only partially mixed during both the wet and dry seasons. The tides propagated asymmetrically and hypersynchronously, with flood dominance during the dry season and ebb dominance during the rainy season. Seasonal variations of the ARP did not significantly affect the hydrodynamic structure of the lower Gurupi estuary. Estuarine turbidity maxima (ETM) were observed in both seasons, although the increase in fluvial discharge during the wet season attenuated and shifted the ETM seaward. Little sediment was delivered to the estuary by the river, and the SSCs were higher at the mouth in both seasons. Sediment was strongly imported during the dry season by tidal asymmetry. The morphology, hydrodynamics, and sediment dynamics all highlight the importance of considering both fluvial discharge and coastal influences on estuaries along the Amazon coast. Full article

(This article belongs to the Special Issue Hydrodynamics in Coastal Areas)

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28 pages, 7296 KiB

Open AccessFeature PaperArticle

Marine Heat Waves over Natural and Urban Coastal Environments of South Florida

by Yannis S. Androulidakis and Vassiliki Kourafalou

Water 2022, 14(23), 3840; https://doi.org/10.3390/w14233840 - 25 Nov 2022

Cited by 4 | Viewed by 3198

Abstract

Marine Heat Wave (MHW) events are increasingly recognized as an important factor in the sustainability of coastal environments (both natural and urban), in the context of climate change. They are related to increasing trends of Sea Surface Temperature (SST) at the adjacent ocean [...] Read more.

Marine Heat Wave (MHW) events are increasingly recognized as an important factor in the sustainability of coastal environments (both natural and urban), in the context of climate change. They are related to increasing trends of Sea Surface Temperature (SST) at the adjacent ocean waters. SST is an important parameter of the earth’s climate and increasing SST trends have been associated with adverse effects on coastal ecosystems, with important environmental and socioeconomic implications. This study focuses on the SST interannual variability over the coastal marine environment of South Florida, which contains several fragile ecosystems, and draws associate effects with adjacent large urban coastal settlements. The methodology is based on high-resolution satellite-derived SST data during a 40-year period (1982–2021), augmented by recent high-resolution model simulations (2012–2020). A generally increasing trend has been detected in the observations over the entire region (0.19 °C/decade). The unusual temperature levels have been associated with the formation of extensive MHW events, which showed interannual positive trends (0.75 events/decade) during the 40-year study period. Specifically, the six most recent years (2015–2021) were characterized by the strongest formation of MHWs with a peak in 2015, 2019 and 2020, with more than 8 events/year and approximately 70 to 110 days/year duration in total. The Florida Keys, especially along the Straits of Florida (southern island coasts), revealed very strong increasing trends. Miami Beach is also characterized by strong interannual trends (1.1 events/decade and 10 days/decade) compared to the enclosed basin of Biscayne Bay. In addition to the influence of atmospheric conditions over all regions around South Florida, the formation of MHWs near the eastern Florida coasts was also controlled by ocean dynamics, related to the warm Florida Current (FC). The evolution of the FC close to the eastern coasts (e.g., Miami Beach) was found to be a pre-condition of MHW formation. Several disastrous events on the biotic environment of South Florida near large urban settlements have been related to the formation of MHWs. The detected positive trends, and especially the recent high peaks of MHW events, may enhance the loss of specific heat-sensitive species, damaging the biodiversity of this tropical coastal environment and weakening the natural coastal protection against tropical storms. Urban planning for sustainable development in South Florida’s coastal cities must take into account MHW trends. Full article

(This article belongs to the Special Issue Hydrodynamics in Coastal Areas)

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