Special Issue "Investigation, Simulation and Application in Hydrodynamics for Coastal and Ocean Engineering"

Dear Colleagues,

The wave spectrum concept, in combination with the linear wave theory for ocean waters, is often used to describe wave propagation at the ocean scale with spectral energy balance. However, the involved physical processes increase in number and complexity as waves move from the deep ocean into coastal waters. To describe the strongly nonlinear dynamics of waves propagating through intermediate-depth waters and the final stages of shoaling and surf zones, fully nonlinear models with improved dispersion characteristics are currently being used. This is a topic that is worthy of major development, yet has remained underinvestigated in recent years.

Vulnerabilities and risks in coastal areas have increased, especially since the midpoint of the last century, and a much more pronounced increase is expected after the midpoint of the current century. It has become clear that human activity is the main cause of such imbalances, both directly, through local actions, and indirectly, through contributions to global warming and climate change. Oftentimes, traditional hard engineering protection techniques, such as the use of breakwaters, groins, seawalls and jetties, have caused a large amount of downdrift erosion problems with high associated costs. In addition, these structures are expensive, have high maintenance costs and may not be sustainable or even effective in reducing wave energy in the medium and long terms. Concerning ecological functions, these structures are not intended to create suitable and attractive environments for fish. On the contrary, these structures are truly short-lived and not eco-friendly. Therefore, the need to manage and maintain coastal areas, focusing on solutions based on nature and conducting research in the design of coastal adaptations for society, is of paramount importance.

Regarding ocean pollution, the natural and atmospheric sources of pollution in the marine environment account for only a small percentage of total ocean pollution (around 16%) when compared to the 37% attributed to urban and industrial loading and to the approximately 45% due to shipping (tank cleaning and unballasting) and oil tanker accidents. No less serious are oil and gas exploration and production operations that have the potential for a variety of impacts on the marine environment, linked to the presence of offshore structures, drilling fluid waste streams, well treatment chemicals and produced water. In addition, offshore drilling physically disrupts the deep-sea habitat and benthic community. The transition to full use of renewable energy will take some time and billions, if not trillions, of euros. More than a quarter of the current oil and gas supply is produced offshore, and it is estimated that by 2040 the amount of offshore energy-related activities will increase. The need to invest in and explore new technologies and equipment, as well as in effective monitoring and control procedures, is therefore becoming increasingly urgent.

This Special Issue aims to support researchers in different areas and assist local communities and coastal managers in carrying out operational coastal management by presenting and discussing management tools and new solutions that should be considered in adaptation programs to be implemented in coastal zones. Submissions describing modeling tools, mathematical developments, numerical implementations and case studies are of interest and will be subject to a peer review process to ensure the publication of high-quality articles.

Prof. Dr. José Simão Antunes Do Carmo
Prof. Dr. José Luís Silva Pinho
Guest Editors

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• deep ocean
• coastal zone
• sea level rise
• ocean pollution
• decision making
• hydrodynamics
• littoral dynamics
• coastal processes
• coastal defenses
• coastal management
• waves and currents
• storms and hurricanes
• adaptation technology
• adaptive management

1. Title: Comparison between Traditional and Digital Image Based Approaches for Beach Sediment Size Characterization. A Case Study at the Nw Portuguese Coast

Authors: José Pinho^1,*; Ana Gomes¹; Willian Melo¹; Isabel Iglesias²; Ana Bio²; José Vieira¹; Helena Granja²

Affiliation: 1. Centre of Territory, Environment and Construction (CTAC), Department of Civil Engineering, University of Minho, Braga, Portugal. [email protected] (J.P.), [email protected] (W.M.), [email protected] (J.V.).

2. Interdisciplinary Centre of Marine and Environmental Research (CIIMAR/CIMAR), University of Porto, Portu-gal. [email protected] (I.I.), [email protected] (A.B.), [email protected], (H.G.)

* Correspondence: [email protected]; Tel.:+351253604720

Abstract: Characterization of beach sediment size and relation to local morphodynamic patterns is of utmost importance to understand coastal vulnerability to erosive processes. Beaches are constituted by mixed sediments that present variable composition and size distributions. Beach sediment grain size characterization is usually based on samples collected at the beach and analysed in laboratory following well stablished standard protocols. These protocols are very time consuming and require a great human resources effort. This paper presents the results obtained for the granulometric analysis of 200 sediment samples collected at different beaches of the northwest Portuguese coast. These samples were analyzed following two methodologies by sieving and applying an image analysis algorithm, based on the wavelet transform method for particle size distribution. From the com-parison of both approaches it is concluded that the results are similar for the obtained D50 char-acteristic diameter of each sample, demonstrating that, for some purposes, sediment size analysis based on digital images could be a very efficient approach.

2. Title: Sea Level Rise Effects on the Sedimentary Dynamics of the Douro Estuary Sand Spit

Authors: Francisca Caeiro-Gonçalves¹; Ana Bio²; Isabel Iglesias²; Paulo Avilez-Valente^1,2,*
Affiliation: 1. Faculdade de Engenharia, Universidade do Porto, Porto, Portugal.

2. Centro Interdisciplinar de Investigação Marinha e Ambiental, Universidade do Porto, Matosinhos, Portugal

* Correspondence: [email protected]

Abstract: This research work focuses on the numerical analysis of the impact of an extreme wave event in the morphodynamics of the Douro estuary sand spit (NW Portugal) under different climate change induced mean sea water level conditions. This sand spit is an important natural defence against the impact of storm events and is partially protected by two breakwaters. Its temporal and spatial dynamics are related to river flow, wave action and wind energy. The storm Christina in January 2014 caused significant damage in the Portuguese Western coast. The storm had origin in a strong low-pressure system that generated large sea waves with long periods, with recorded maximum waves heights of 13.5 m and 15 m at the Leixões’ and Sines’ buoys, respectively. We use a combination of numerical models to study the effect of a Christina-like storm on the morphology of the Douro sand spit, under mean sea level rise conditions induced by climate change. SWAN was used for hydrodynamics and XBeach for hydrodynamics and morphodynamics assessments. SWAN software is applied for the implementation, calibration, and validation of a regional Ibero-Atlantic wave hydrodynamics model, with a dynamic downscaling to a higher resolution coastal model covering a 28 km-long (S–N) nearshore location. Modelling of sediment dynamics at the sea-land interface is performed using XBeach on a local model (6 km × 6 km) with wave and tidal conditions fed by the SWAN coastal model. No river flow was considered in the simulations. The study focuses on the storm short-term (two days) sand spit morphodynamics impact, in terms of its erosion/accretion patterns. The analysis is concentrated in three scenarios, a present day’s scenario, and the IPCC’s SSP2-4.5 and SSP5-8.5 medium confidence scenarios for the year 2100. For each of the IPCC scenarios, three mean sea level values were considered for the 0.05, 0.50 and 0.95 prob-abilistic percentiles. The wave conditions are those resulting from a Christina storm-like event. Results show that an increase in the predicted mean sea level rises will induce a slight increase in the erosion/accretion areas in the waveward side of the sand spit. Overtopping of the southern breakwater was registered alongside the possibility of wave overwashing of the sandspit for the highest simulated mean sea level values simulated.

3. Title: Simulation of Saltwater Intrusion in the Minho River Estuary under Sea Level Rising Scenarios

Authors: Guilherme Menten¹; Willian Melo¹; José Pinho^1,*; Isabel Iglesias²; Ana Bio²; José Vieira¹
Affiliation: 1. Centre of Territory, Environment and Construction (CTAC), Department of Civil Engineering, University of Minho, Braga, Portugal. [email protected] (G.M.), [email protected] (J.P.), [email protected] (W.M.), [email protected] (J.V.).

2. Interdisciplinary Centre of Marine and Environmental Research (CIIMAR/CIMAR), University of Porto, Portu-gal. [email protected] (I.I.), [email protected] (A.B.)

* Correspondence: [email protected]; Tel.:+351253604720

Abstract: Estuaries are high vulnerable areas to climate changes impacts both by eventual fluvial discharges modifications and by sea level rising effects. This paper presents the simulation results of saltwater intrusion at the Minho River estuary under climate changes scenarios, using both 2DH and 3D approaches of Delft3D software. The obtained results demonstrated that, although there is no significant stratification, there was a difference in the obtained results between the two used model approaches. In the worst sea level rise scenario, the length of the saline intrusion reaches up to 28 km from the river mouth with the 2DH model and 30 km with the 3D model. It was concluded that the 3D model results are more precise, but both are able to give insights on how the saltwater intrusion will be affected by the climate change conditions. Among that, it was demonstrated that river flow discharges are the main determinant factor on saltwater intrusion in the Minho estuary, having more impact than sea level rise. This shows that the adopted flow discharges at the upstream reservoirs can be a good way to control the saltwater intrusion along the estuary in the future.