Tidal Conditions Research Articles

Simulation of sand and mud transport processes in currents and waves by time-dependent 2DV model

This paper presents a time-dependent, two-dimensional vertical model for the simulation of sand and mud concentrations, transport and bed level changes in tidal conditions with or without surface waves. The model solves the advection-diffusion equation for suspended sediment. The horizontal velocities and the sediment mixing coefficients are modelled as function of x, z and t. The settling velocity is constant or modelled as function of the sediment concentration. The sediment mixing coefficient over the water depth is described by flexible expressions based on current and wave parameters which can be modified easily in the input file. To represent mud flocculation and hindered settling processes, the settling velocity can be set as constant or concentration-dependent (input). The bed boundary condition is modelled as a bed concentration as function of the bed-shear stress. The model is valid for low and high sand and mud concentrations including fluid mud concentrations. The numerical SUSTIM2V-model is herein used to simulate sand and mud transport as measured in tidal waters. The model is also successfully used for simulation of high mud concentrations in the near-bed region as measured in the mouth of the Amazon River. The model has also been used to simulate scour along an offshore caisson-type foundation structure.

New insights into combined surfzone, embayment, and estuarine bathing hazards

Abstract. Rip currents are the single largest cause of beach safety incidents globally, but where an estuary mouth intersects a beach, additional flows are created that can exceed the speed of a typical rip current, significantly increasing the hazard level for bathers. However, there is a paucity of observations of surfzone currents at estuary mouth beaches, and our understanding and ability to predict how the bathing hazard varies under different wave and tide conditions are therefore limited. Using field observations and process-based XBeach modelling at an embayed, estuary mouth beach, we demonstrate how surfzone currents can be driven by combinations of estuary discharge and wave-driven bathymetric and boundary rip currents under various combinations of wave and tide forcing. While previous studies have demonstrated the high hazard that rip currents pose, typically during lower stages of the tide, here we demonstrate that an estuary mouth beach can exhibit flows reaching 1.5 m s−1 – up to 50 % stronger than typical rip current flows – with a high proportion (> 60 %) of simulated bathers exiting the surfzone during the upper half of the tidal cycle. The three-dimensional ebb shoal delta was found to strongly control surfzone currents by (1) providing a conduit for estuary flows that connect to headland boundary rips and (2) acting as a nearshore bar system to generate wave-driven “river channel bathymetric rips”. Despite significant spatio-temporal variability in the position of the river channels on the beach face, it was possible to hindcast the timing and severity of past bathing incidents from model simulations, providing a means to forewarn bathers of hazardous flows.

Distinct molecular responses of mangrove plants to hypoxia and reoxygenation stresses contribute to their resilience in coastal wetland environment

Mangroves adapt to periodical submergence and constitute resilient ecosystems in coastal environments. The question is whether they can sustain long submergence stress when sea level rises as a consequence of climate change. To address this, seedlings of two representative mangrove species that acclimate to low to mid tide (Avicennia marina) and mid to high tide (Kandelia obovata) conditions were treated with continual submergence for 7 days as extended hypoxia, or semi-diurnal cyclic submergence and reoxygenation for 7 days. At specific time points, leaves were collected to construct RNA-Sequencing libraries for gene expression analysis. Through the lens of transcriptome, the initial response of A. marina to submergence was mild but more dramatic after prolong immersion. However, the initial response of K. obovata was drastic and reduced in latitude later, suggesting distinct species-specific responses. After adapting to diurnal cycles, both species minimized transcriptome fluctuations similarly. Metabolically, during initial response, sucrose and starch were converted into glucose for fermentation to increase glycolytic flux, coupled with regeneration of NAD+. The energy amelioration was accompanied by longer term phytohormone regulations where ethylene signal transduction pathway was enhanced, but abscisic acid biosynthesis was reduced. Notably, gibberellic acids biosynthesis increased in A. marina but decreased in K. obovata as a unique feature. Genomic level analysis indicated that only about 30 % of the conserved plant submergence responsive genes were expressed during submergence in these mangroves. The function of an ethylene responsive gene was validated in transgenic Arabidopsis. This research elucidates distinct molecular mechanisms and metabolic pathways that empower A. marina and K. obovata to endure prolonged submergence and hypoxia. By highlighting their unique adaptive strategies in response to rising sea levels, these findings enhance our understanding of mangrove resilience and provide insights for the conservation and management of these essential coastal ecosystems in the face of climate change.

Characteristic Analysis of Vertical Tidal Profile Parameters at Tidal Current Energy Site

Many mathematical models have been proposed to estimate vertical tidal current profiles. However, as previous studies have shown that tidal current energy sites have different characteristics in their vertical tidal current profiles, it is necessary to estimate the profiles from field-measured data for practical purposes. In this study, we measured layered tidal currents over two months using an acoustic Doppler current profiler (ADCP) to analyze the characteristics of vertical tidal current profiles at the Jangjuk Strait, a candidate site for tidal current energy. As a result, the power law parameter α and bed roughness β were estimated as 4.51–12.41 and 0.38–0.42, respectively. Additionally, the maximum roughness length representing seabed roughness in the logarithmic profile was estimated as 0.221 m, and the estimated friction velocity was 0.038–0.194 m/s. Furthermore, a high correlation was observed between the depth-averaged tidal current velocity and friction velocities at all sites during flood and ebb tide conditions. A high correlation was also found between the bed roughness, roughness length, and power law exponent at relatively deeper sites. Tidal current energy sites display distinct characteristics compared to other sea areas. Therefore, it is essential to account for field conditions when conducting numerical modeling and design.

Flood Mapping using HEC-RAS and GIS: A Case Study of Palembang Watersheds

Flooding is a significant issue in Palembang City, affecting areas such as Gandus, Lambidaro, Boang, Sekanak, Bendung, Kidul, Buah, Juaro, Selinca, Nyiur, Aur, Sriguna, Kedukan, Keramasan, Kertapati and Jakabaring watershed. This research contributes to flood control measures by providing flood mapping and modelling for decision-makers and local authorities. The main objective of this paper is to perform a steady flow analysis to study the hydraulic characteristics of flow; velocity and water surface profile of the adjacent research areas. There are three processes involved in the data analysis: hydrological, hydraulic and spatial. The calculation of average rainfall is performed using the Isohyet method with the assistance of the IDW 3D Analyst tool in ArcGIS and the design discharge is calculated using the HSS Nakayasu method. The hydraulic analyses involve river morphology extraction using RAS Mapper tools in HEC-RAS. Steady flow simulations are conducted for normal water depth conditions and the highest tidal conditions. The simulation result is then reclassified and the flood location points are verified with observed data. For normal water depth conditions, the maximum water level in the Lambidaro watershed reaches 2,09 meters, which covers a flood area of 721,53 ha. Meanwhile, based on the highest tidal simulations, the maximum water level in the Selinca watershed reaches 3,21 meters, covering a flood area of 209,36 ha.

Investigating the Performance of Glass Fibre-Reinforced Polymer (GFRP) in the Marine Environment for Tidal Energy: Velocity, Particle Size, Impact Angle and Exposure Time Effects

Tidal energy, with its potential to provide a consistent energy output and reduce carbon emissions, has garnered significant interest. This study, which evaluates the performance of tidal turbine blades in seawater conditions and with sand particles, presents a novel approach. A slurry rig was developed to examine composite materials, and a glass fibre-reinforcement polymeric material was tested over a range of particle sizes, velocities, and impact angles. In addition, this paper used a new test protocol with 14 days (336 h) and 91 days (2184 h) of pre-exposure time of materials before testing. The results, which show significant changes in the erosive mechanisms of GFRP in short- and long-term pre-exposure time as a function of these variables, have profound implications for the design and performance of tidal turbine blades. The study also utilised scanning electron microscopy (SEM), depth profiling analysis, and erosion mapping techniques to compare the erosion behaviours of GFRP. These tools can be used to optimise such materials in tidal turbine conditions.

Marsh topography reveals the signature of storm-surge-driven sedimentation

Salt marshes are valuable tidal landforms threatened by drowning due to increasing sea levels. Marsh accretion supported by sediment settling during repeated flooding potentially offsets the relative elevation loss. Although tidal flooding is commonly depicted as the main mechanism delivering the sediment to marshes, storm surges and waves may deeply affect tidal flow conditions and sediment reworking in shallow tidal systems, thus raising questions on the relative contribution of these processes to salt-marsh accretion. Here we show that storm surges substantially sustain the marsh sediment budget, locally contributing up to 90% of sedimentation, and critically influence depositional patterns by analyzing a 3-yr-long measurement record of sedimentation on the marshes in the Venice Lagoon (Italy). Surge-enhanced water levels promote wind-wave-driven sediment fluxes directly across the tidal flat-marsh transition, altering tidal sedimentation patterns and, thus, affecting marsh topographic elevation and morphology. By comparing sedimentation patterns and topographic profiles, we show that the signature of storm-surge sedimentation can be found in marsh topography, which we suggest therefore as an easily detectable indicator of the relative contribution of the different physical processes driving marsh vertical evolution. The comparison with other marshes worldwide, characterized by different tidal ranges and wave exposure, consistently supports the link between the salt-marsh topographic profile and the physical processes controlling marsh evolution.

Effects of varied inundation characteristics on early life stages of a salt marsh plant

Tidal inundation is a major stress in salt marshes that regulates the patterns of plant distribution and the associated functions provided by vegetation communities. Usually, frequency is used to represent inundation intensity and can be estimated using elevation. However, frequency is only a statistical indicator of tidal inundation conditions during a given period, which ignores many details of tidal inundation characteristics based on a single tidal event. On the scale of a single tidal event, duration and water depth are important characteristics for describing inundation conditions, which vary along the elevation gradient. The frequency of tidal events of a specific duration and water depth also varied. To unravel the impact of varied inundation characteristics on the key life stages of a foundation plant, we designed an experiment with varied inundation treatments of different frequencies, durations, and depths. Our results showed that the frequency, duration, and depth of inundation events significantly influenced seed emergence, seedling survival, and growth. Stress can be strengthened by a higher frequency with a longer duration and larger depth. Among these factors, frequency had a dominant impact, followed by duration and water depth. Specifically, there is a trade-off between frequency, duration, and depth, suggesting that an inundation event with shallower depth and/or shorter duration would reduce the stress from higher frequency. The findings fill a gap in the loss of details of varied inundation characteristics on plant establishment on a fine scale. Further, it will help explicit inundation stress more accurately and clearly and provide important implications for stress relief solutions in coastal ecological restoration.

Buffer properties in the Guadalquivir Estuary (SW Iberian Peninsula)

The Guadalquivir Estuary (main source of continental waters to the Gulf of Cadiz) has a carbonate basin, which enables the transport of inorganic carbon to adjacent coastal areas. Therefore, in order to study the dynamic of the carbonate system and its buffer capacity, a total of 12 samplings were carried out from 2017 to 2022. Samplings included longitudinal transects and tidal cycles in different seasonal and tidal conditions. Total alkalinity (TA) and dissolved inorganic carbon (DIC) showed increased values upstream, while calcium (Ca2+) presented the highest values in most of the marine samples. The ranges values obtained for these three variables were of 2180–5140 μmol kg−1, 430–3950 μmol kg−1 and 1295–10,855 μmol kg−1 for TA, DIC and Ca2+, respectively. Two buffer factors (βDIC and βH) were also calculated to study the variability of the buffer capacity of the Guadalquivir Estuary. These indicate that the estuary is well buffered for salinities above 10, while the inner part is more vulnerable to acidification effects. Using a non-linear 1D hydrodynamic model, net inorganic carbon system transports were calculated, showing that the Guadalquivir Estuary is exporting TA, DIC and Ca2+ to the Gulf of Cadiz.

Can We Protect China's Northern Coast Wetlands From Tidal Dynamics by Restoring Native Species After Spartina alterniflora Is Eradicated? A Model‐Based Analysis

ABSTRACTIn recent years, the Chinese government has implemented a series of initiatives with the objective of eradicating the invasive Spartina alterniflora along the entire coastline. This has given rise to concerns about the potential for subsequent coastal erosion and salt marsh shrinkage. This study introduces a novel contribution in the form of a model‐based analysis, grounded in fieldwork from the Yellow River Delta, which assesses the potential of native Suaeda salsa as an alternative for coastal protection. Our approach is distinctive in that it not only compares the flow velocity reduction effects of S. alterniflora and S. salsa, but also evaluates the efficacy of three distinct planting patterns in managing tidal dynamics. In this study, we present a significant finding: while both species can mitigate tidal flow velocity, S. alterniflora shows superior performance, which represents a novel point of discussion in the field of coastal wetland management. Furthermore, our research indicates that dense aggregated planting patterns are particularly effective during storm surges, offering a strategic insight for future ecological engineering. However, we recognize the potential limitations of our approach, including the need for continuous management to control the spread of S. alterniflora and the necessity for further research to optimize the restoration potential of S. salsa under varying tidal conditions. Our findings highlight the importance of a balanced approach, suggesting the retention of a portion of S. alterniflora while also emphasizing the strategic planting of S. salsa in high‐density configurations to enhance coastal resilience.

Conditional Effects of Tides and Waves on Sediment Supply to Salt Marshes

AbstractThe survival of salt marshes, especially facing future sea‐level rise, requires sediment supply. Sediment can be supplied to salt marshes via two routes: through marsh creeks and over marsh edges. However, the conditions of tides and waves that facilitate sediment import through these two routes remain unclear. To understand when and how sediment is imported into salt marshes, 2‐month measurements were conducted to monitor tides, waves, and suspended sediment concentration (SSC) in Paulina Saltmarsh, a meso‐macrotidal system. The results show that the marsh creek tends to import sediment during neap tides with waves. A tidal cycle with a small tidal range result in weaker flow in the marsh creek during ebb tides, reducing the export of sediment. Waves enhance sediment supply to the marsh creek by eroding mudflats. However, strong waves can directly resuspend sediment in marsh creeks during spring tides when the water level is above the marsh canopy, enhancing sediment export through creeks. Net sediment import over marsh edges requires the opposite tidal and wave conditions: spring tides with weak waves. Spring tides provide stronger hydrodynamics, facilitating sediment import over the marsh edge. Increased SSC during the ebb phase can occur with strong waves over the marsh edge, resulting in net sediment export. Therefore, the net import or export of sediment, through the creek and over the marsh edge, depends on the combination of tidal and wave conditions. These conditions can vary between estuaries and even individual marshes. Understanding these conditions is crucial for better management of salt marshes.

Insights into PFAS contaminants before and after sewage discharges into a marine protected harbour

Per and polyfluoroalkyl substances (PFAS) and their degradation products are a concern to human and ecosystem health. Wastewater treatment plants are not efficient at removing PFAS compounds and are thought to be a major source of these compounds to marine environments. The sewerage infrastructure in the UK, has over 20,000 combined stormwater overflows (CSOs). These CSOs are relief values whereby untreated wastewater can discharge under permit from the Environment Agency with exceptional rain/snowfall conditions. CSOs discharged 3.6 million monitored hours of untreated wastewater into English rivers and coasts in 2023. Concerns have been raised about the proximity of these CSO discharges to highly protected marine habitats. This study is the first to determine that PFAS concentrations are elevated in a highly protected marine bay (Langstone Harbour, England) following recent sewage releases compared to an extended period without discharge. Analysis was carried out into a suite of 54 PFAS compounds of which only one (PFHpA) was detectable above LOD prior to discharges but 8 afterwards. These included banned PFOS (Linear and Branched 8.6 ng/L ∓ 0.90) and PFOA (2.9 ng/L ∓ 0.29) which were above annual average EQS for inland and ‘other’ surface waters. Most of the PFAS compounds detected doubled in concentration above LODs. These two-fold increases we discuss are likely conservative estimates based on the use of LODs and tidal conditions. Additional Oysters (Crassostrea gigas) and Seaweed (Fucus vesiculosus) were taken revealing high concentrations of the shorter chain PFBA (6.99μg/kg ∓ 2.42 ww) in seaweed samples. These seaweeds were calculated to have conservative bioaccumulation factors (BAF) > 6000 for PFBA indicating these algae might be an important reservoir of some PFAS contamination. We discuss these results in the context of the largescale discharges of untreated wastewater nationally and globally, and call upon a need for a better understanding of the transfer of PFAS contaminants into marine food chains.

Study on the Characteristics of Tidal Current Velocity in Estuarine and Bay Areas

Abstract In estuarine and bay regions, reciprocating tidal currents frequently constitute the predominant hydrodynamic forces. Nonetheless, there exists a paucity of research concerning the hydrodynamic characteristics under intricate tidal conditions. This study employs tidal current data collected from nine sites within the Yellow River Estuary and Hangzhou Bay to examine the periodic characteristics of tidal currents, the vertical velocity distribution, and the attributes of ebb and flood peak velocities. The study revealed that the Yellow River Estuary and Hangzhou Bay predominantly exhibit nearly symmetrical reciprocating tidal currents. Nevertheless, certain regions within Hangzhou Bay also demonstrate asymmetrical tidal currents. The vertical velocity distribution throughout various phases of a single tidal cycle generally adheres to the characteristics described by the SOULSBY distribution. The peak velocities of ebb and flood tides are correlated with the rate of change in water depth (hm/tm), and an equation for calculating these peak velocities has been derived through fitting data.

Numerical investigation for the influence of suspended sediment on salinity distribution in the Qiantang Estuary, China

Numerous studies have demonstrated that high suspended sediment concentration (SSC) can change density distribution and affect water mixing, but few scholars have investigated this impact on numerical simulations of estuarian salinity distribution. The Qiantang Estuary is a macro-tidal estuary with high SSC, which has a more significant influence on water density than that of salinity. Therefore, this paper established a three-dimensional (3D) numerical model coupling flow, salinity and SSC based on Delft3D and first analyzes the impact of SSC on salinity distribution under different runoff and tidal conditions in the Qiantang Estuary. The results indicated that simulated salinity generally decreases when considering the impact of SSC, suggesting a weakening effect on saltwater intrusion. The distribution of salinity difference (ΔS) and SSC show a strong spatial and temporal correlation, and ΔS peak increases and shifts upstream as the tidal range increases or runoff discharge decreases. The mechanism of SSC influencing saltwater intrusion can be summarized as follows: On the one hand, SSC increases the water density, which weakens the driving force for saltwater to move upstream, causing a decrease in flood current velocity and water level, and thereby diminishing the advective transport of salinity. On the other hand, SSC enhances density stratification, which weakens vertical turbulence and reduces the dispersive transport of salinity. These combined effects reduce both the advective and diffusive salinity fluxes during the flood tide, ultimately leading to a decrease in upstream salinity. Therefore, neglecting this effect in estuaries with high SSC can cause significant deviations in salinity simulation results, especially under low-flow and high-tide conditions.

Drying-Wetting Correlation Analysis of Chloride Transport Behavior and Mechanism in Calcium Sulphoaluminate Cement Concrete.

In response to rising CO2 emissions in the cement industry and the growing demand for durable offshore engineering materials, calcium sulphoaluminate (CSA) cement concrete, known for its lower carbon footprint and enhanced corrosion resistance compared to Ordinary Portland Cement (OPC), is increasingly important. However, the chloride transport behavior of CSA concrete in both laboratory and marine environments remains underexplored and controversial. Accordingly, the chloride ion transport behaviors and mechanisms of CSA concrete in laboratory-accelerated drying-wetting cyclic environments using NaCl solution and seawater, as well as in marine tidal environments, were characterized using the rapid chloride test (RCT), X-ray diffraction (XRD), mercury infiltration porosimetry (MIP), and thermogravimetric analysis (TGA). The results reveal that CSA concrete accumulates more chloride ions in NaCl solution than in seawater, with concentrations 2-3.5 times higher at the same water-cement ratio. Microscopic analysis indicates that calcium and sulfate ions present in seawater facilitate the regeneration of ettringite, thereby increasing the density of the surface pore structure. The hydration and repair mechanisms of CSA concrete under laboratory conditions closely resemble those in marine tidal conditions when exposed to seawater. Additionally, this study found that lower chloride ion concentrations and pH levels inhibit the formation of Friedel's salt. Therefore, laboratory experiments with seawater can effectively simulate CSA concrete's chloride transport properties in marine tidal environments, whereas NaCl solution does not accurately reflect actual marine conditions.

Assessing sediment CO2 effluxes in the coastal ecosystem of North Sumatra, Indonesia

Coastal wetlands including mangrove play a vital role in regulating the local and global carbon cycle. Coastal areas contribute greatly to the carbon exchange process due to the complex interactions that occur between the atmosphere, land, and oceans. One of the important components in coastal carbon dynamics is CO2 gas exchange between soil, water and the atmosphere. This study aims to assess CO2 efflux across various land covers (namely natural mangrove, restored mangrove, and converted mangroves to oil palm and aquaculture pond) in the coastal areas of North Sumatra Province, and analyze the effect of sea tides and ebbs on the rate of CO2 efflux and their connection with the number and area of macrozoobenthos burrows. We applied direct sampling by using the static closed chamber method attached to portable CO2 analyzer. The mean of CO2 efflux in natural mangrove forest land covers was 866±585 mgCO2/m2/h during low tide conditions and 1137±792 mgCO2/m2/h during high tide conditions, followed by oil palm plantations at 760.71±341 mgCO2/m2/h, restored mangroves during low tide of 575.24±326 mgCO2/m2/h and 597.11±180 mg CO2/m2/h during high tide conditions, and the lowest was recorded in ponds at 588.55±358 mgCO2/m2/h. Further, we observed that tidal conditions affect the magnitudes of CO2 efflux in natural and restored mangrove forests, and we did not observe similar pattern in oil palms and ponds since these land covers were not influenced by regular tidal input. We also observed that no significant relationship between the number and area of macrozoobenthos burrows and CO2 efflux. Our findings suggest that CO2 effluxes in coastal wetlands are highly dynamic and presumably driven by complex factors and therefore, understanding their magnitudes and drivers requires extensive measurement covering large spatial and temporal scales.

Rapid prey switching of juvenile snapper (Chrysophrys auratus) in response to fluctuating visibility

ABSTRACT This study investigates the feeding behaviour of juvenile (0+) snapper (Chrysophrys auratus) in an estuarine nursery habitat. Underwater video footage recorded across a range of tidal states and times of day revealed a shift in foraging mode that was strongly related to water clarity. Fish exclusively ate benthic prey when horizontal water visibility was <4 m, but plankton dominated their diet in clearer water. The percentage of plankton in the diet also decreased later in the day, and on the outgoing tide. To our knowledge, this is the first documented evidence of daily prey-switching behaviour in wild juvenile snapper in New Zealand. Our findings highlight the adaptive foraging strategies of juvenile snapper as well as the potential ecological impacts resulting from anthropogenic alterations in water quality, which likely affect many marine species.

Enhancing structural durability in marine concrete piles with initial defects: RS-AAT-induced advection to suppress chloride ion penetration

Chlorine-induced corrosion in unsaturated, cracked, and delaminated reinforced concrete structures is a major cause of lifespan decline in marine wet and dry zones. Reverse-seepage and Saturation based Active Anti-corrosion Technology (RS-AAT) has the scientific basis and application potential to solve this problem due to its unique saturation and reverse-seepage effects provided by structural construction means. This study introduces an analytical framework for understanding time-dependent chloride ion permeation in concrete pipe piles, incorporating the combined impact of cracks, delamination, and RS-AAT anti-corrosion approach. The analytical approach is validated through finite element method simulations and a comprehensive 90-day indoor experiment, which simulate marine submerged and tidal conditions. Extensive parametric analysis further elucidates advection-induced suppression of chloride ion diffusion by RS-AAT in cracked and delaminated conditions, considering chloride ion diffusion coefficient and water permeability coefficient, reverse-seepage pressure, initial crack characteristics and centrifugal stratification. Results show that RS-AAT substantially inhibits chloride ion penetration and lengthens the lifespan of concrete piles, even initially cracked or delaminated. This work provides a basis for RS-AAT’s application and optimization as an innovative approach to enhancing marine concrete infrastructure.

Simulating cross-scale flow dynamics around offshore monopile foundations with a GFD-CFD coupled model

Flow dynamics are complex and undergo significant impact from offshore engineering infrastructures, such as wind turbines, involving interactions across different temporal and spatial scales. Individual numerical models of geophysical fluid dynamics (GFD) or computational fluid dynamics (CFD) face challenges in accurately representing these dynamics. To effectively capture the three-dimensional cross-scale flow around offshore infrastructures, we propose a generalized coupling framework that integrates the unstructured-grid Finite-Volume Community Ocean Model (FVCOM) for GFD and the Open Field Operation and Manipulation (OpenFOAM) for CFD. With the validation against the flume experiment, the common-boundary nesting method was developed to allow an accurate representation of flow dynamics around offshore hydraulic infrastructures. Idealized monopile foundation experiments demonstrate the model's capability to capture the formation of Karman vortex street, rotating horseshoe vortex under realistic astronomical tidal conditions. Application of this coupling framework to the offshore wind farm in Yangjiang, China, reveals flow direction lagging of 15° in the wake of a monopile under diurnal tide. This coupling approach, leveraging the strengths of both CFD and GFD models, provides a universal downscaling methodology in geophysical conditions, for a better understanding of the impact of offshore hydraulic infrastructures on the surrounding environment and further planning offshore engineering projects.

Application of GIS Spatial Analysis for the Assessment of Storm Surge Inundation Risks in the Guangdong–Macao–Hong Kong Great Bay Area

This study evaluates the storm surge inundation risk in three anthropogenically infilled estuaries—Xichong, Renshan, and Kaozhouyang—located in the Guangdong–Macao–Hong Kong Great Bay Area, China. By integrating GIS spatial analysis with storm surge modeling, we conducted 204 numerical experiments to simulate storm surge inundation under varying typhoon intensities and astronomical tide conditions. Results revealed that coastal terrain plays a crucial role in influencing storm surge levels and inundation extents. Specifically, the pocket-shaped terrain in the Renshan and Kaozhouyang estuaries amplified storm surges, resulting in higher inundation levels compared to the relatively open terrain of Xichong. Furthermore, anthropogenically reclaimed land in these estuaries appear to be particularly vulnerable to storm-induced inundation. Overall, this study underscores the importance of considering coastline morphology and the anthropogenic modifications of coastal terrain in storm surge risk assessments, offering valuable insights for disaster prevention and mitigation strategies. The use of ArcGIS spatial analysis coupled with storm surge modeling, facilitated by high-resolution DEMs, provides a statistical risk assessment of inundation. However, more complex flooding dynamics models need to be developed, particularly when terrestrial bottom friction information, which is heavily modified by human activities, can be accurately incorporated.