Hydrodynamics and Water Quality in Coastal Systems: Numerical Modelling and Observations

A special issue of Journal of Marine Science and Engineering (ISSN 2077-1312). This special issue belongs to the section "Physical Oceanography".

Deadline for manuscript submissions: 20 August 2025 | Viewed by 8444

Special Issue Editors

Physics Department, CESAM, University of Aveiro, 3810-193 Aveiro, Portugal
Interests: numerical modelling of coastal systems; physical/biological/chemical interactions; remote sensing; estuaries and lagoons; coastal zone monitoring; atmosphere–ocean processes; water quality
Special Issues, Collections and Topics in MDPI journals
Physics Department, CESAM, University of Aveiro, 3810-193 Aveiro, Portugal
Interests: estuarine and coastal physical oceanography; stratification/mixing; estuarine biogeochemistry; hydrodynamic and biogeochemical modelling
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Coastal systems are important transition zones connecting ocean and land, from where they make contact with a large number of particulate and dissolved materials (e.g., sediments, nutrients, and organic matter). These systems support productive ecosystems and high biological diversity, providing valuable ecosystem services, including salinity intrusion, nutrient recycling, natural conditions for aquaculture, nursery, and the removal of pollutants. However, coastal systems are among the areas most threatened by anthropogenic pressures, since they host large and growing populations, and also suffer from the substantial deterioration of marine water quality. Thus, an understanding of hydrodynamic behaviors, varied water properties, and water quality is necessary to develop suitable management practices.

This Special Issue seeks to collate a set of publications that enable an advanced understanding of hydrodynamics and water quality in coastal systems (tidal propagation, salinity intrusion, nutrients, eutrophication, harmful algal blooms, hypoxia, trace metals, acidification, etc.), taking advantage of numerical modeling and observations. Methods and results on hydrodynamic/water quality variability for present and future climates are welcome. We thus invite researchers to submit research articles, reviews, and case studies.

Dr. Ana Picado
Dr. Nuno Vaz
Guest Editors

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Keywords

  • water quality
  • numerical modelling
  • nutrients
  • oxygen
  • coastal systems

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Published Papers (7 papers)

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Research

15 pages, 3983 KiB  
Article
Estuarine Floc Mass Distributions from Aggregation/Disaggregation and Bed Sediment Exchange
by William H. McAnally, Ashish J. Mehta, Andrew J. Manning and Carola Forlini
J. Mar. Sci. Eng. 2025, 13(3), 615; https://doi.org/10.3390/jmse13030615 - 20 Mar 2025
Viewed by 235
Abstract
Estuarine benthos, among other lifeforms of interest to water quality, can be sensitive to size-distributed suspended cohesive flocs. In such a context, tide-dependent floc mass distributions in the Tamar Estuary in the UK are revisited. At the field site close to maximum turbidity, [...] Read more.
Estuarine benthos, among other lifeforms of interest to water quality, can be sensitive to size-distributed suspended cohesive flocs. In such a context, tide-dependent floc mass distributions in the Tamar Estuary in the UK are revisited. At the field site close to maximum turbidity, time-series of the water level, current velocity, salinity, and suspended sediment concentration (SSC) were recorded in 1998 over several tidal cycles. Concurrently, at selected times and elevation, floc mass distributions were derived from in situ observations of the SSC, floc diameters, and settling velocities. A previously developed time-dependent model, revised to account for both multiclass floc aggregation/disaggregation and bed sediment exchange by erosion and deposition, is applied to simulate mass distributions during ebb/flood cycles on 24 June and 5 August. Although the model does not account for the density effects of salinity or sediment advection, limited comparisons between simulated and observed mass distributions indicate generally good agreement in median diameter prediction on both days. This concurrence is due to the primary role of suspended floc dynamics and only a secondary contribution from bed sediment exchange in governing floc properties. For a better prediction of the SSC variation with the tide, the effects of salinity and advection can be incorporated by coupling the modeled floc dynamics with a suitable multi-dimensional hydrodynamic code. Full article
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22 pages, 11125 KiB  
Article
Spatial Variability Analysis of Renewal Time in Harbour Environments Using a Lagrangian Model
by Yaiza Samper, Ivan Hernández, Leidy M. Castro-Rosero, Maria Liste, Manuel Espino and José M. Alsina
J. Mar. Sci. Eng. 2025, 13(2), 341; https://doi.org/10.3390/jmse13020341 - 13 Feb 2025
Viewed by 513
Abstract
The water quality in port domains is highly dependent on the capacity for renewal and mixing with external water. This study uses Lagrangian modelling to investigate renewal time in Barcelona, Tarragona, and Gijón harbours (Spain), which represent semi-enclosed micro-tidal and meso-tidal environments. For [...] Read more.
The water quality in port domains is highly dependent on the capacity for renewal and mixing with external water. This study uses Lagrangian modelling to investigate renewal time in Barcelona, Tarragona, and Gijón harbours (Spain), which represent semi-enclosed micro-tidal and meso-tidal environments. For this purpose, different particle-tracking simulations have been carried out in each of the ports to study the trends of circulation and water renewal trends both on the surface layer and at the bottom. The results indicate that in microtidal Mediterranean ports, the renewal time is longer at the bottom (32 days in Barcelona and 61 days in Tarragona). Conversely, in the mesotidal port of Gijón, located on the Cantabrian coast, the opposite pattern is observed, with higher renewal times at the surface (14 days). While the results from Lagrangian modelling exhibit magnitudes comparable to in situ measurements from previous studies, it remains essential to evaluate the specific characteristics of each method and compare these findings with other similar works. Full article
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22 pages, 2172 KiB  
Article
Coupled Hydrodynamic and Biogeochemical Modeling in the Galician Rías Baixas (NW Iberian Peninsula) Using Delft3D: Model Validation and Performance
by Adrián Castro-Olivares, Marisela Des, Maite deCastro, Humberto Pereira, Ana Picado, João Miguel Días and Moncho Gómez-Gesteira
J. Mar. Sci. Eng. 2024, 12(12), 2228; https://doi.org/10.3390/jmse12122228 - 5 Dec 2024
Cited by 1 | Viewed by 1129
Abstract
Estuaries are dynamic and resource-rich ecosystems renowned for their high productivity and ecological significance. The Rías Baixas, located in the northwest of the Iberian Peninsula, consist of four highly productive estuaries that support the region’s economy through key fisheries and aquaculture activities. Numerical [...] Read more.
Estuaries are dynamic and resource-rich ecosystems renowned for their high productivity and ecological significance. The Rías Baixas, located in the northwest of the Iberian Peninsula, consist of four highly productive estuaries that support the region’s economy through key fisheries and aquaculture activities. Numerical modeling of biogeochemical processes in the rias is essential to address environmental and anthropogenic pressures, particularly in areas facing intense human development. This study presents a high-resolution water quality model developed using Delft3D 4 software, integrating the hydrodynamic (Delft3D-FLOW) and water quality (Delft3D-WAQ) modules. Calibration and validation demonstrate the robust performance and reliability of the model in simulating critical biogeochemical processes, such as nutrient cycling and phytoplankton dynamics. The model effectively captures seasonal and spatial variations in water quality parameters, including water temperature, salinity, inorganic nutrients, dissolved oxygen, and chlorophyll-a. Of the variables studied, the model performed best for dissolved oxygen, followed by nitrates, phosphates, ammonium, silicate, and chlorophyll-a. While some discrepancies were observed in the inner zones and deeper layers of the rias, the overall performance metrics aligned closely with the observed data, enhancing confidence in the model’s utility for future research and resource management. These results highlight the model’s value as a tool for research and managing water and marine resources in the Rías Baixas. Full article
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18 pages, 4406 KiB  
Article
A Baroclinic Fluid Model and Its Application in Investigating the Salinity Transport Process Within the Sediment–Water Interface in an Idealized Estuary
by Jun Zhao, Liangsheng Zhu, Bo Hong and Jianhua Li
J. Mar. Sci. Eng. 2024, 12(11), 2107; https://doi.org/10.3390/jmse12112107 - 20 Nov 2024
Viewed by 767
Abstract
Understanding the salinity transport process around the sediment–water interface is important for water resources management in the upper reach of an estuary. In this study, we developed a baroclinic fluid dynamic model for investigating the flow and salt transport characteristics within the sediment–water [...] Read more.
Understanding the salinity transport process around the sediment–water interface is important for water resources management in the upper reach of an estuary. In this study, we developed a baroclinic fluid dynamic model for investigating the flow and salt transport characteristics within the sediment–water interface under tidal forcing. The validation showed robust model performance on the salinity transport within the sediment–water interface. The results revealed that the turbulent kinetic energy, dissipation rate, and kinetic energy production rate exhibited periodic variations within the seabed boundary layer. The thickness of the viscous sublayer and the mean flow showed an inverse relationship. Water and salinity exchange within the sediment–water interface occurred predominantly via turbulent diffusion, with extreme turbulent kinetic energy production rates appearing during the tidal reversal, flood, and ebb stages. The sediment acted as a source of salinity release during ebb tides and a sink for salinity absorption during flood tides. As the sediment depth increased, fluctuations in salinity were weakened. These results clearly illustrated that the sediment layer is important in modulating the salinity transport in the upper reach of an estuary. However, such an important process was usually excluded by previous studies. The model developed in this study can be used as a sediment–water interface module that, coupled with other hydrodynamic models, can evaluate the contributions of the sediment layer to the salinity exchange in coastal water. Full article
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14 pages, 13322 KiB  
Article
Composite Risk Assessment of HNS Discharged from Marine Industrial Facilities: A Case Study on Incheon Port, South Korea
by Taeyun Kim, Jun-Ho Maeng, Eunchae Kim, Bohyun Yeo, Seongjun Si, Jihyeon Nam, Sunho Kim, Changkyum Kim, Jae-Jin Park, Tae-Sung Kim and Moonjin Lee
J. Mar. Sci. Eng. 2024, 12(11), 1915; https://doi.org/10.3390/jmse12111915 - 27 Oct 2024
Cited by 1 | Viewed by 953
Abstract
This study conducted a composite risk assessment to evaluate the environmental impacts of phenol, a Hazardous and Noxious Substance (HNS) released or leaked from port facilities. The study area was designated as the vicinity of Incheon Port, South Korea, where the volume of [...] Read more.
This study conducted a composite risk assessment to evaluate the environmental impacts of phenol, a Hazardous and Noxious Substance (HNS) released or leaked from port facilities. The study area was designated as the vicinity of Incheon Port, South Korea, where the volume of petrochemical-related materials is substantial and various industrial facilities are located. For the composite risk assessment, various vulnerability maps were developed, incorporating the dispersion range of phenol calculated through numerical modeling. The vulnerability maps were generated by classifying socio-environment, legally protected areas, habitats, and species, followed by integrating these individual vulnerability maps to construct an integrated vulnerability map. The composite risk assessment was conducted by considering both the integrated vulnerability map and the dispersion range of phenol. The assessment results indicated that the highest risk by depth was observed in the lower layers due to the settling characteristics of phenol. Spatially, areas where islands and coastlines converge exhibited relatively higher risks. This was attributed to the high concentrations of phenol released from industrial facilities, such as crude oil refineries, petrochemical plants, and organic compound manufacturers, in regions characterized by intense human activity, sensitive habitats, and legally protected areas. Continuous monitoring of these high-risk areas is crucial for assessing the environmental impacts of HNS substances like phenol. Full article
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23 pages, 4409 KiB  
Article
Assessing Present and Future Ecological Status of Ria de Aveiro: A Modeling Study
by Ana Picado, Humberto Pereira, Nuno Vaz and João Miguel Dias
J. Mar. Sci. Eng. 2024, 12(10), 1768; https://doi.org/10.3390/jmse12101768 - 5 Oct 2024
Cited by 1 | Viewed by 1254
Abstract
Coastal lagoons hold significant ecological value due to their rich biodiversity and essential roles in supporting ecosystems. However, they are increasingly threatened by accelerated climate change, and it is crucial to assess these environments’ ecological status for present and future conditions resulting from [...] Read more.
Coastal lagoons hold significant ecological value due to their rich biodiversity and essential roles in supporting ecosystems. However, they are increasingly threatened by accelerated climate change, and it is crucial to assess these environments’ ecological status for present and future conditions resulting from the impacts of climate change. In this context, the present work aims to evaluate the present and future ecological status of Ria de Aveiro through the application of the numerical model Delft3D. The model was validated, and the results demonstrate that it effectively captures the main characteristics of the lagoon dynamics, although achieving accurate water quality representation poses challenges due to interdependencies in solutions and the inherent complexity of associated processes. The model was explored to characterize the environmental factors of the lagoon and evaluate its ecological status through the computation of several indexes. According to the model results, the main environmental factors present seasonal variations consistent with temperate climates. Regarding the ecological status of Ria de Aveiro, the central channels of the lagoon mostly hold a Good/Moderate status, while regions near river inflows tend to exhibit Moderate to Poor conditions. In future conditions, water quality is expected to improve in winter and autumn due to reductions in river-borne pollutants resulting from the projected decrease in river flow. For spring and summer, a decline in water quality is projected mainly due to the increase in phosphate concentrations in the lagoon. This study provides valuable insights into the ecological dynamics of coastal lagoons under changing climatic conditions, contributing to improved management and mitigation strategies. The findings can guide future conservation efforts and help mitigate the adverse effects of climate change on these vital ecosystems. Full article
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25 pages, 9279 KiB  
Article
Implementation of a Far-Field Water Quality Model for the Simulation of Trace Elements in an Eastern Mediterranean Coastal Embayment Receiving High Anthropogenic Pressure
by Aikaterini Anna Mazioti, Vassilis Kolovoyiannis, Evangelia Krasakopoulou, Elina Tragou, Vassilis Zervakis, Georgia Assimakopoulou, Alexandros Athiniotis, Vasiliki Paraskevopoulou, Alexandra Pavlidou and Christina Zeri
J. Mar. Sci. Eng. 2024, 12(5), 797; https://doi.org/10.3390/jmse12050797 - 10 May 2024
Cited by 2 | Viewed by 1992
Abstract
Water quality modeling is a key element for the support of environmental protection and policymaking. The aim of this work is to describe the application of a far-field water quality model for the simulation of marine pollution occurring from heavy metals (cadmium, lead, [...] Read more.
Water quality modeling is a key element for the support of environmental protection and policymaking. The aim of this work is to describe the application of a far-field water quality model for the simulation of marine pollution occurring from heavy metals (cadmium, lead, nickel, copper, and zinc). The highly stressed marine area of the Saronikos Gulf (Aegean Sea, Eastern Mediterranean) was chosen for investigation. Major pollution sources were identified, loads were estimated, and the model was parameterized to reproduce the local seawater conditions. The distribution of the pollutants between the dissolved and particulate phases was examined. The performance of the model set-up was evaluated using field concentration measurements. The described implementation succeeded in reproducing the observed levels of pollution and therefore can be used as a baseline configuration to examine the cumulative impact of future pollution sources; for example, accidental pollution events. Full article
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