Search Results (137)

Climate change is projected to significantly alter hydrological conditions across the Northern Hemisphere, with increased precipitation variability, more intense rainfall events, and earlier, rain-driven spring floods in regions like northern Sweden. These changes will affect both natural ecosystems and hydropower-regulated rivers, particularly during ecologically sensitive periods such as the grayling spawning season in late spring. This study examines the impact of extreme spring flow conditions on grayling spawning habitats by analyzing historical runoff data and simulating high-flow events using a 2D hydraulic model in Delft3D FM. Results show that previously suitable spawning areas became too deep or experienced flow velocities beyond ecological thresholds, rendering them unsuitable. These hydrodynamic shifts could have cascading effects on aquatic vegetation and food availability, ultimately threatening the survival and reproductive success of grayling populations. The findings underscore the importance of integrating ecological considerations into future water management and hydropower operation strategies in the face of climate-driven flow variability. Full article

Against the backdrop of increasingly depleted global non-renewable resources, research on renewable energy has become urgently critical. As a significant marine clean energy source, tidal current energy has attracted growing scholarly interest, effectively addressing global energy shortages and fossil fuel pollution. Semi-enclosed bay straits, with their geographically advantageous topography, offer substantial potential for tidal energy exploitation. China’s Bohai Strait exemplifies such a geomorphological feature. This study focuses on the Bohai Strait, employing the Delft3D model to establish a three-dimensional numerical simulation of tidal currents in the region. Combined with the Flux tidal energy assessment method, the tidal energy resources are evaluated, and exploitation recommendations are proposed. The results demonstrate that the Laotieshan Channel, particularly its northern section, contains the most abundant tidal energy reserves in the Bohai Strait. The Laotieshan Channel has an average power flux density of 50.83 W/m², with a tidal energy potential of approximately 81,266.5 kW, of which about 12,189.97 kW is technically exploitable. Particularly in its northern section, favorable flow conditions exist—peak current speeds can reach 2 m/s, and the area offers substantial effective power generation hours. Annual durations with flow velocities exceeding 0.5 m/s total around 4500 h, making this zone highly suitable for deploying tidal turbines. To maximize the utilization of tidal energy resources, installation within the upper 20 m of the water layer is recommended. This study not only advances tidal energy research in semi-enclosed bay straits but also provides a critical reference for future studies, while establishing a foundational framework for practical tidal energy development in the Bohai Strait region. Full article

Marsh vegetation dampens wave energy, providing protection to coastal communities from storms. A new modeling framework was applied to study wave height evolution over the saltmarsh bordering Newbury, MA. A regional Delft3D hydrodynamic model generated wind driver waves in the open water portions of the study area, which were then one-way coupled with an analytical model, the Marsh Transect Wave Attenuation (MTWA) model, which tracked wave evolution along select transects throughout the marsh. Field observations of vegetation and wave height evolution were used to calibrate MTWA. Seven scenarios were run covering a range of possible future management and environmental conditions, in addition to projected sea level rise. Results underscore the importance of vegetation and elevation to wave attenuation. Full article

Ria de Arousa, one of the Rias Baixas, presents very high economic value for the Galician communities due to its importance for aquaculture, but the changes associated with climate change are expected to have an impact on its hydrodynamics and consequently on the production of cultivated species. The main objective of this work is to study the impact of climate change on the circulation and hydrography of the Ria de Arousa, considering the SSP5-8.5 scenario defined by IPCC. To achieve this goal, the Delft3D hydrodynamic model was implemented three-dimensionally using the results obtained from the CMIP6 MPI-ESM1-2-HR climate model as boundary conditions. Future changes in the hydrodynamic and hydrographic circulation of this coastal system were analysed. The model results were used to assess the impact of climate change on water temperature, salinity, and density patterns of the Ria de Arousa, as well as on stratification, Brunt–Väisälä frequency, and residual circulation. During summer, the water temperature is higher at the surface and lower at the bottom, likely due to the intrusion of water from the Eastern North Atlantic Central Water (ENAWC). In the future, this pattern will continue, albeit with higher temperatures, as the water temperature is expected to increase by around 2.2 °C by 2100. During winter, the water temperature at the bottom is warmer than at the surface, indicating a thermal inversion typical of this season. In the future, the water temperature will also increase, although the increase will be lower compared to summer, with a value of approximately 0.5 °C. Salinity will decrease in the summer and increase in the winter, especially in the areas closest to the rivers. Density analysis shows vertical homogeneity in the water column during winter and stratification during summer. During winter, the Brunt–Väisälä frequency (N) is higher in the region closest to the river’s mouth and lower near the ocean. In the summer, the N value decreases with depth. In the future, the density will increase in winter and decrease in summer, and stratification is expected to decrease. Regarding the residual circulation, it was observed that it will strengthen in the summer and weaken in the winter due to a decrease in freshwater runoff. However, the positive circulation pattern observed in the present will be maintained in the future. Full article

Estuaries are dynamic ecosystems with crucial environmental, economic, and social functions, driving extensive hydro-morphological research supported by numerical modeling. This study systematically reviews estuarine modeling applications over the past 15 years to identify commonly used tools, model configurations, and validation strategies, to examine regional trends in the application, and to explore and discuss the relative emphasis on hydrodynamic, sediment transport, and morphological modeling within the selected studies. Following the PRISMA 2020 methodology, a comprehensive search in Scopus and Web of Science identified 3926 articles, from which 197 met the eligibility criteria. Each study was analyzed to assess modeling software, mesh types, dimensional configurations, and validation parameters. Results indicate that DELFT3D is the most widely used tool, followed by TELEMAC and FVCOM, with a preference for two-dimensional models and structured meshes. Model accuracy, assessed through Skill Scores, confirms their reliability in representing estuarine dynamics. Additionally, findings reveal significant geographical disparities, with China leading research efforts, while Latin America and Africa remain underrepresented. This gap highlights the need to expand modeling efforts in these regions to enhance estuarine management and resilience. Strengthening numerical modeling in diverse contexts will improve the predictive capacity of hydro-morphological processes, supporting sustainable decision-making in estuarine environments. Full article

Renewable energy sources such as hydropower are important to reduce the global emissions. Hydropower, however, comes with other environmental challenges by altering the ecological conditions in the rivers. Hydraulic models connected with fish habitat models could be one tool to assess the environmental impacts and evaluate mitigation measures for fish habitats. This study examines the limitations of steady-state hydraulic simulations in a low-sloping river located between two hydropower plants, where downstream regulations significantly influence the river flow dynamics. A 2D hydrodynamic model in Delft3D FM was applied to compare steady-state and transient simulations, focusing on how hydraulic variables affect the spawning habitat. The results show that steady-state models fail to capture time-dependent damping and delayed water level responses, leading to systematic underestimation of hydraulic variability. Peak bed shear stress values were under-predicted by the steady-state interpolation, which may under-predict spawning ground stability. Additionally, the steady-state approach failed to capture daily habitat fluctuations, resulting in a mean absolute error of 2910 m² in spawning habitat area per hour. This study demonstrates how errors in hydraulic calculations propagate into habitat assessments, potentially leading to misleading long-term evaluations of fish populations. This study highlights the importance of selecting appropriate hydraulic modelling approaches based on river-specific flow dynamics. Future studies should investigate the sensitivity of fish habitat models to hydraulic inputs from steady-state and transient simulations by integrating these approaches into advanced fish modelling tools, such as individual-based models. This will help determine the optimal balance between computational efficiency and accuracy in long-term habitat assessments. Full article

River nodes play a crucial role in regulating water and sediment transport within river networks. The SiXianJiao (SXJ) node serves as a key exchange point between the West River (WR) and North River (NR) in the Pearl River Delta (PRD), South China. Understanding the differences in flood diversion dynamics between X-shaped and H-shaped configurations under varying geomorphic conditions is essential for flood management. This study employs the Delft3D-Flow model to investigate the flood diversion mechanisms of these composite river nodes. Results revealed distinct hydrodynamic behaviors: the X-shaped node facilitates greater water exchange due to a shared channel segment, whereas the H-shaped node experiences restricted exchange due to flow resistance in the connecting branch. Both configurations exhibit self-regulating flood diversion processes that significantly reduce flood risks. A critical flow fraction of approximately 75.9% [WR/(WR + NR)] is identified, at which water levels (WLs) at both ends of the SXJ node almost equalize. When the WR flow fraction exceeds this threshold, floodwaters are diverted toward the NR. Below it, the diversion direction reverses. Additionally, flood diversion synchronizes asynchronous flood waves, stabilizing the discharge fraction at Makou (Sanshui), which fluctuates around 75.8% (24.2%) for the X-shaped node and 76.6% (23.4%) for the H-shaped node. These findings enhance our understanding of flood diversion dynamics and provide valuable insights for optimizing flood mitigation strategies and hydraulic infrastructure planning in the PRD and comparable river systems worldwide. Full article

The Pacitan Regency is at risk of megathrust earthquakes and tsunamis due to the seismic gap along the southern region of Java Island, making risk-reduction efforts crucial. This research aims to analyse the tsunami risk associated with a potential megathrust earthquake scenario in Pacitan’s coastal areas and develop sustainable mitigation strategies. The research employs spatial analysis to evaluate the risk and subsequently formulate strategies for long-term mitigation. A weighted overlay method was utilised to integrate hazard (H) and vulnerability (V) datasets to produce a tsunami risk map (R). The hazard component was modelled using a tsunami propagation simulation based on the Shallow Water Equations in the Delft3D-Flow software, incorporating an earthquake scenario of Mw 8.8 and H-loss calculations in ArcGIS Pro 10.3. The vulnerability assessment was conducted by overlaying population density, land use, and building footprint from the Global Human Settlement Layer (GHSL) datasets. Finally, sustainable strategies were proposed to mitigate the tsunami risk effectively. The results show that Pacitan faces significant tsunami disaster risk, with tsunami waves at the coast reaching 16.6 m. Because the coast of Pacitan is densely populated, mitigation strategies are necessary, and in the present contribution, the authors developed holistic spatial planning, which prioritise the preservation and restoration of natural barriers, such as mangroves and coastal forests. Full article

A high-resolution numerical model called Delft3D (5 km resolution) forced with realistic high-frequency atmospheric conditions was set up to describe the circulation pattern in the Red Sea basin. The validation of the model was performed considering several tide gauge data, the SST of AVHRR/Pathfinder, and the available literature. The model outcomes show that the general circulation pattern in the Red Sea is dominated by energetic anticyclonic eddies consistent with observations in terms of both size and magnitude. We conducted two scenarios of numerical experiments considering thermohaline and wind forcing to investigate the main driving mechanism of the circulation patterns. When simulated using full forcing (wind and thermohaline), the wind forcing experiment mostly reproduces the circulation patterns. On the other hand, thermohaline forcing generates weaker circulation patterns with cyclonic eddy dominance. The model effectively replicates the reversal of the three-layer exchange flow system at the Bab el Mandeb Strait, which is enhanced by both wind and thermohaline forcing. The simulation indicates that subsurface inflow deflects along the eastern coastline of the southern part of the Red Sea. Full article

In the presented work, design conditions for breakwaters were derived from offshore climate reanalysis data (ERA5), which were downscaled to the nearshore by two numerical approaches, i.e., SwanOne and Delft3D, for different average and extreme wave and weather conditions. Model validation was performed using in situ measurements. The advantages and disadvantages of both numerical approaches were investigated. Both models showed sufficient accuracy according to measurements in the field, where SwanOne offers a simple and fast calculation method, while Delft3D provides a more complete representation, not only of waves but also current dynamics. However, it requires a much broader amount of input parameters and more complex boundary conditions. Then, SwanOne was applicable to calculate nearshore wave characteristics based on the input parameters extracted from the statistical analysis of long-term ERA5 data. Based on this process, design wave heights and periods at the nearshore were determined for 10- to 100-year return periods. For breakwater design on the west coast of the Mekong Delta, maximum wave heights in a range of 1.1 m to 1.3 m at a distance of 100 m to 300 m could be determined for a return period of 20 years, corresponding to water depths of 2.33 m and 2.88 m, respectively. Full article

Different scenarios have been established and simulated based on the Delft3D model to compare and assess the impact of human activities (increased pollutants as oxygen demand, BOD, COD, nutrients, and land reclamation), climate change (rising temperatures, sea level rise), and a combined scenario of human activities and climate change on water quality in the Cat Ba–Ha Long coastal area. The findings quantify the impacts of anthropogenic activities and climate change on the water quality in the study area in 2030 and 2050. During the northeast monsoon and the two transitional seasons, the impact of humans and climate change adversely affects water quality. The impact of climate change is less significant than that of human activities and their combination, which result in a reduction in DO levels of 0.02–0.13 mg/L, 0.07–0.44 mg/L, and 0.09–0.48 mg/L, respectively. Meanwhile, during the southwest monsoon, climate change significantly reduces water quality (0.25–0.31 mg/L), more so than human activities (0.14–0.16 mg/L) and their combined effects (0.13–0.17 mg/L). This may elucidate the fact that the increase in nutrient supply from the river during the southwest monsoon in this region can result in an increase in nutrient levels and biological activity, which, in turn, causes an increase in DO. Additionally, the augmented quantity of DO may partially offset the decrease in DO resulting from climate change. Under the influence of human activities and climate change, the nutrient levels in the area increase, with average values of 0.002–0.033 g/m³ (NO₃⁻), 0.0003–0.034 g/m³ (NH₄⁺), and 0.0005–0.014 g/m³ (PO₄³⁻). Full article

This study employs the Delft3D numerical model to elucidate nonlinear interactions in velocity dynamics across four key marine regions during typhoon-induced storm surges (Typhoon In-fa, No. 2106). To address gaps in understanding how typhoon winds drive storm surges, this study aims to analyze the relative contributions of bottom friction, wind stress, and convective terms to storm surge dynamics, providing insights for predictive modeling and marine hazard mitigation. Introducing a novel metric, the “Flow Velocity Nonlinear Coupling Proportion” (“FVNCP”, abbreviated as “NCP”), this research quantifies the interactive effects of storm surge flow velocity by dissecting the contributions of bottom friction, wind stress, and the convective term. Through decision tree modeling, wind stress emerges as the primary driver of NCP in open sea and sheltered areas, with peak values reaching 1.50 × 10⁻⁴ and 2.14 × 10⁻⁴ m/s², respectively. In contrast, the convective term dominates the strait and bypassing regions, exhibiting maximum impacts of 3.21 × 10⁻⁴ and 2.94 × 10⁻⁴ m/s², while bottom friction’s influence is consistently minor across all regions. Wind stress contributes the most to NCP in open waters, at an average of 48.28%, while the convective term exerts a comparable 38.85% effect. In confined areas like the strait and bypassing regions, the convective term accounts for 40–44% of the NCP, with wind stress contributing 32–39%. The role of bottom friction is the least among the three factors though its impact intensifies in shallower zones. These findings offer critical insights for advancing predictive models and informing strategies to mitigate typhoon-driven marine hazards. Full article

Owing to the high tidal range, the Severn Estuary and Bristol Channel have the potential to generate huge amounts of renewable electricity for the UK. During the flood tide, the surging water travels upstream to form the Severn Bore. This study explores the dynamics of the Severn Bore through hydrodynamic modelling, analyzing how the tidal amplitude, mean water level, and river discharge affect the bore’s intensity, reach, and sustainability. The Delft3D simulations show that the downstream tidal amplitude plays a critical role. Tides with an amplitude of less than 6 m will lead to the disappearance of the Severn Bore. The mean water level also significantly influences the bore’s propagation, with a 1.5 m drop resulting in a 15 km retreat of the bore. A high river discharge rate weakens the bore’s intensity and reduces its reach. These findings underscore the need for careful planning in tidal energy development within the Severn Estuary. Excessive exploitation of tidal energy can be detrimental to the Severn Bore and the ecological function of the estuary. Full article

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

This paper presents a comparative study that examines the effects of the Dubai Creek extension on its hydrodynamics and water flushing dynamics. Dubai Creek (Khor Dubai) is a 24 km long artificial seawater stream located in the emirate of Dubai. The creek has experienced the impact of the rapid urbanization of Dubai and a major 13 km extension project, which connected the creek to the Arabian Gulf from the other side. In this paper, two-dimensional hydrodynamic and flushing models were created using Delft3D Flexible Mesh (2021.03) to investigate the water circulation and water quality of the creek before and after the extension. The hydrodynamic models were calibrated and validated to accurately simulate water levels and currents with correlation values close to 1 and very small RMSE and bias. Flushing models were created to simulate water renewal along the creek. The results of the flushing models showed a significant improvement in the flushing characteristics of pollutants in terms of the residence times of the extended creek (Existing Creek) model compared to the old one (Old Creek). This improvement emphasized the positive impact of the creek extension project on the local aquatic ecosystem and its overall water quality. Full article