Search Results (12,510)

Temporal alterations in coastlines depict the significant changes in coastal areas, driven by both natural processes and human activities. For island nations, monitoring of the coastline is essential due to their vulnerability to such impacts. In this study, Funafuti Atoll, an archipelago of small and scattered islands around the capital of Tuvalu, is selected as the study region, and the aim is to extract coastlines of different islands and investigate coastal area changes between 2019 and 2023 using Sentinel-2 imagery. A simple linear iterative clustering-based superpixel segmentation and adaptive thresholding approach is employed for coastline extraction. Initially, superpixel segmentation is conducted to cluster 3-band image pixels into coherent regions, excluding the sea area. Subsequently, the normalized difference vegetation index (NDVI) is calculated, and the superpixels are used to obtain corresponding NDVI regions, on which adaptive Gaussian thresholding is applied to extract coastlines. Finally, the areas enclosed by the extracted coastline boundaries are utilized for change analysis. The results indicate that islands along the western rim of Funafuti exhibited significant alteration (an average decrease of −14.48%), whereas those along the eastern rim remained relatively stable due to the presence of coral rubble ridges and steep slopes. The change analysis revealed that from 2019 to 2020, approximately 15.1 hectares (ha) were eroded, resulting in a net area change rate of −4.14%. Between 2020 and 2021, erosion increased to 20.2 ha, yielding a net change of −7.75%. From 2021 to 2022, 13.2 ha were eroded, corresponding to a −1.74% change. From 2022 to 2023, a net gain of 10.3 ha occurred (+0.25%), primarily due to land reclamation along the lagoon-facing coast of Fongafale Island. Overall, all islands showed a decreasing area trend between 2019 and 2023, with an average net change of −12.97%. The coastal changes occurred along the sand-dominated coast with gentle slopes, possibly driven by the impact of tropical cyclones, prolonged swells, and coastal flooding, which act as the primary driving forces for the study region. Full article

Tight oil reservoirs are characterized by low porosity, low permeability, and low saturation, making it difficult to achieve economic development through conventional water injection. This study experimentally evaluated different injection media and oil displacement methods and used nuclear magnetic resonance methods to explain the micro mechanisms of oil displacement during different oil displacement processes. The experiments showed that supercritical CO₂ flooding and supercritical CO₂ and active water alternating flooding were much more useful for low-permeability reservoirs compared with conventional water flooding. This technology can increase the recovery rate by more than 12.0%, which is 33.24% higher than the rate achieved with conventional water injection. In addition, it can effectively improve the rapid increase in water content caused by the rapid advance in the water front during the water injection process. The NMR results indicated good consistency for the recovery efficiency of pores under different oil displacement conditions. When the aperture varied between 0.1 µm and 1 µm (type III), the utilization rate was highest, followed by type IV (1–10 µm), type II (0.01–0.1 µm), and type I (0.001–0.01 µm). By comparison, conventional water and CO₂ alternating flooding was more effective for type III pores, increasing oil recovery by 12.58%, while active water + CO₂ alternating flooding can further drive oil, increasing oil recovery by 33.24% and greatly displacing oil in micro-pores and macro-pores. Full article

This study investigated the hydraulic characteristics of a self-rotating flood barrier (SRFB) by performing laboratory experiments. The SRFB is proposed as a secure solution to withstand both waves and sudden water level rise, thereby protecting the coastal area behind it. The SRFB is designed to rotate and rise automatically by buoyancy when the water level exceeds a certain threshold or waves start to overtop the crest level of the caisson, where the barrier is enclosed. The barrier begins to rise when the chamber is filled with enough water for the buoyancy force to exceed its own weight. The performance of the structure was tested under various regular wave conditions at different water depths. Pressure transducers were placed along the front face of the barrier to measure the wave pressures acting on it. The barrier’s angular displacement was also identified using synchronized video footage during the measurements. The results showed that the overall magnitude of the measured pressures increased with water depth due to the larger volume of water inflow from overtopping waves. During the rise in the barrier, the pressure profiles dynamically varied with the rotation angle as the pattern of water flow into the chamber changed depending on the test cases. Analysis results showed how the pressures are distributed along the barrier at the moment of peak wave force. These findings would provide fundamental information for estimating design wave forces on the structure. Full article

Coastal high tide flooding doubled in the U.S. between 2000 and 2022 and sea level rise (SLR) due to climate change will dramatically increase exposure and vulnerability to flooding in the future. However, standards for elevating buildings in flood hazard areas, such as base flood elevations set by the Federal Emergency Management Agency, are based on historical flood data and do not account for future SLR. To increase flood resilience in flood hazard areas, federal, state, regional, and municipal planning initiatives are developing guidance to increase elevation requirements for occupied spaces in buildings. However, methods to establish a flood elevation that specifically accounts for rising sea levels (or sea level rise-adjusted design flood elevation (SLR-DFE)) are not standardized. Many municipalities or designers lack clear guidance on developing or incorporating SLR-DFEs. This study compares guidance documents, policies, and methods for establishing an SLR-DFE. The authors found that the initiatives vary in author, water level measurement starting point, SLR scenario and timeframe, SLR adjustment, freeboard, design flood elevation, application (geography and building type), and whether it is required or recommended. The tables and graph compare the different initiatives, providing a useful summary for policymakers and practitioners to develop SLR-DFE standards. Full article

This study offers a novel perspective on the role of bridges as agents of urban transformation by examining their influence on the morphological development of Valencia (Spain) from the 13th century to the catastrophic flood of 1957. Traditionally viewed as mere connective infrastructure, bridges are reframed here as key structuring elements that shaped urban expansion, resilience strategies, and socio-spatial dynamics. Through an innovative classification based on stages of bridges, the research integrates historical cartography, cadastral data, and Geographic Information Systems (GIS) to trace how successive waves of bridge construction aligned with distinct socio-political, environmental, and technological contexts. The study demonstrates that bridge development not only facilitated territorial connectivity but also directed urban growth patterns, enabled functional zoning, and responded adaptively to flood risk and demographic pressure. The case of Valencia is particularly significant in light of contemporary challenges in climate adaptation and sustainable urban planning. By unveiling bridges as morphological and functional drivers of urban form, this research offers transferable insights for cities worldwide grappling with the legacy of riverine geographies and the pressures of resilient transformation. Full article

This study presents an integrated workflow for the characterization of fault-controlled fractured–vuggy reservoirs, demonstrated through a comprehensive analysis of the TP12CX fault zone in the Tahe Oilfield. The methodology establishes a four-element structural model—comprising the damage zone, fault core, vuggy zone, and cavern system—coupled with a multi-attribute geophysical classification scheme integrating texture contrast, deep learning, energy envelope, and residual impedance attributes. This framework achieves a validation accuracy of 91.2%. A novel structural element decomposition–integration approach is proposed, combining deterministic structural reconstruction with facies-constrained petrophysical modeling to quantify reservoir properties. The resulting models identify key heterogeneities, including caverns (Φ = 17.8%, K = 587 mD), vugs (Φ = 3.5%, K = 25 mD), and fractures (K = 1400 mD), with model reliability verified through production history matching. Field application of an optimized nitrogen foam flooding strategy, guided by this workflow, resulted in an incremental oil recovery of 3292 tons. The proposed methodology offers transferable value by addressing critical challenges in karst reservoir characterization, including seismic resolution limits, complex heterogeneity, and late-stage development optimization in fault-controlled carbonate reservoirs. It provides a robust and practical framework for enhanced oil recovery in structurally complex carbonate reservoirs, particularly those in mature fields with a high water cut. Full article

Flooding frequency in the lower Yellow River (YR) exhibited an abrupt increase post-934 CE, causing catastrophic societal disruptions. However, the quantitative relationship between this abrupt increase and the intensification of human activity in the midstream Loess Plateau (LP)’s Primary Sediment Source Area (PSSA) remains uncertain. This study systematically evaluates the threshold effects of human activities on YR flooding through multi-proxy historical records, GIS-based spatial analysis, and nonparametric statistical tests. The results show that from 934 to 1102 CE, the population density in the PSSA surged from 1.3 to 19.8 persons/km² (a 14.2-fold increase, p = 0.005). A 2400-year-scale comparison using 934 CE as the breakpoint revealed that the mean population density in this region increased from 5.2 to 51 persons/km² (a 9.8-fold increase). This dramatic population surge drove a 1.4-fold increase in the cultivation rate (from 8.6% to 20.5%), leading to a 5.4-fold rise in sediment yield (1.6 × 10⁸ → 1.02 × 10⁹ t/yr, p = 0.035), a 10-fold acceleration in downstream sedimentation rate (0.3 → 3.3 cm/yr, p = 0.001), and ultimately a 5.5-fold escalation in flooding frequency (from 1.6 to 10.4 events per 20 years, p < 0.0001). The study identifies 19.8 persons/km² as the ecological pressure threshold. It proposes converting population density to ecological pressure equivalents adjusted for soil–water conservation coverage (e.g., terracing/afforestation). When the equivalent ecological pressure exceeds 19.8 persons/km², pre-defined sediment control measures (e.g., tillage restrictions/afforestation mandates) should be enforced in the PSSA. Full article

The steam flooding–gravity drainage technology has become one of the effective alternative development methods in the middle and later stages of thin-layer ultra-viscous oil steam throughput, with predicted recovery rate of over 50%. Currently, there is a lack of relevant technical research on the composite swallowing and spitting preheating stage. This is in response to the slow preheating of the oilfield and the large differences in connectivity between injection and production wells. The dynamic analysis method was used to analyze the key factors that restrict the efficient connectivity of steam throughput preheating. Based on this, a series steam throughput preheating efficient connectivity technologies were proposed. Physical simulation, numerical simulation, and other methods were used to characterize and demonstrate the technical principles and operating of the efficient connectivity technology. The research results were successfully applied to the super-viscous oil reservoirs of the Fengcheng oilfield in Xinjiang. The results show that the main factors severely limiting the balanced and rapid connectivity between injection and production wells are the limited radius of steam coverage, low utilization degree oil layers, and frequent unilateral steam breakthroughs. The reservoir expansion transformation has improved the reservoir properties along the horizontal section, increasing the utilization rate of the horizontal section from 51% to 90%, achieving rapid connectivity injection and production wells, and shortening the conventional throughput preheating cycle by 3–4 cycles. The group combination steam injection method achieved a centralized increase in thermal energy, with the inter-well connectivity changing from unidirectional to a broader area The reasonable steam injection intensity was 15 t/m, the regional temperature field increased from 83 °C to 112 °C, and the steam area expanded by approximately 10 m. The multi-medium composite technology achieved a dual increase in steam coverage and profile utilization, with the steam coverage radius increasing by 15 m and the oil reservoir profile utilization increasing by more than 30%. The temporary plugging and fracturing of the reservoir achieved the sealing of inherited breakthrough channels, directing the steam to unused areas, increasing the utilization rate to 89.2%, and shortening the throughput preheating cycle by 3 cycles. This series of technologies has achieved remarkable results in actual application in super-heavy oilfield, which has certain reference significance for the efficient and low-carbon development of heavy oil steam throughput reservoir turning into drive and release. Full article

The AP2/ERF (APETALA2/ethylene-responsive element binding factor) family represents one of the largest transcription factor families in plants, playing pivotal roles in abiotic stress responses and hormone signaling pathways. Through genome-wide analysis, we identified 163 AnAP2/ERF genes in Adiantum nelumboides. Transcriptome data revealed that 12 AnAP2/ERF genes were significantly upregulated under either drought or flooding stress, with 8 genes responding to both conditions. qRT-PCR validation confirmed that all 12 selected AnAP2/ERF genes exhibited differential expression under both stress types. Notably, these genes also showed significant induction by abscisic acid (ABA), auxin (IAA), and gibberellin (GA), suggesting their potential involvement in stress responses through hormone crosstalk. This study establishes a foundation for investigating AnAP2/ERF gene functions and their molecular mechanisms in abiotic stress adaptation in A. nelumboides. Full article

This study uses remote sensing data to assess susceptibility to hazards, which are then validated to model impact scenarios for land subsidence and coastal flooding in the Integrated Coastal Zone Management (ICZM) of Selangor, Malaysia, to support decision-making in urban planning and land management. Land subsidence and coastal floods affect a major proportion of the population in the ICZM, with subsidence being significant contributing factors, but information on the extent of susceptible areas, monitoring, and wide-area coverage is limited. Land subsidence distribution is demarcated using Interferometric Synthetic Aperture Radar (InSAR) time-series data (2015–2022), and integrated with coastal flood susceptibility derived from Analytic Hierarchy Process (AHP)-based weights to model impacts on land cover. Results indicate maximum subsidence rates of 46 mm/year (descending orbit) and 61 mm/year (ascending orbit); reflecting a gradual increase in subsidence trends with an average rate of 13 mm/year. In the worst-case scenario, within the ICZM area of 2262 km², nearly 12% of the total built-up land cover with the highest population density is exposed to land subsidence, while exposure to coastal floods is relatively larger, covering nearly 34% of the built-up area. Almost 27% of the built-up area is exposed to the combined effects of both land subsidence and coastal floods, under present sea level conditions, with increasing risks of coastal floods over 2040, 2050 and 2100, due to both combinations. This research prioritizes areas for further study and provides a scientific foundation for resilience strategies aimed at ensuring sustainable coastal development within the ICZM. Full article

Rapid urbanization and climate change have intensified urban flood risks, necessitating resilient upstream infrastructure to ensure metropolitan water security and effective flood mitigation. Gravity dams, as critical components of urban flood protection systems, regulate discharge to downstream urban areas. Gravity dams are critical for regulating flood discharge, yet their seismic vulnerability poses significant challenges, particularly under compound effects involving concurrent seismic loading and climate-induced elevated reservoir levels. This study introduces a novel seismic analysis framework for gravity dams using the scaled boundary finite element method (SBFEM), which efficiently models dam–water and dam–foundation interactions in infinite domains. A two-dimensional numerical model of a concrete gravity dam, subjected to realistic seismic loading, was developed and validated against analytical solutions and conventional finite element method (FEM) results, achieving discrepancies as low as 0.95% for static displacements and 0.21% for natural frequencies. The SBFEM approach accurately captures hydrodynamic pressures and radiation damping, revealing peak pressures at the dam heel during resonance and demonstrating computational efficiency with significantly reduced nodal requirements compared to FEM. These findings enhance understanding of dam behavior under extreme loading. The proposed framework supports climate-adaptive design standards and integrated hydrological–structural modeling. By addressing the seismic safety of flood-control dams, this research contributes to the development of resilient urban water management systems capable of protecting metropolitan areas from compound climatic and seismic extremes. Full article

Surfactant flooding has shown potential in enhanced oil recovery (EOR), but conventional surfactants often underperform in heterogeneous reservoirs. This study investigates the impact of a surfactant mixture, combining anionic sodium dodecyl sulfate (SDS) and zwitterionic oleylamidopropyl betaine (OAB-30), on two-phase flow behavior and its EOR potential. Six surfactant solutions with varying concentrations were first screened using an idealized dead-end shaped microchannel in combination with interfacial properties and rheological tests. The results showed that 0.2% SDS and 0.6% OAB-30 produced the highest oil recovery in the dead-end structure. Interfacial tension was reduced to 0.374 mN/m and strong viscoelastic behavior was observed using the optimized surfactant mixture. Wettability of the surface tended to be more hydrophilic after the application of the surfactant mixture as well. Subsequently, the microscale oil displacement process was examined using the optimized surfactant mixture via microfluidic devices with an idealized pore–throat network with permeability contrast and realistic pore–throat structure. The application of the optimal surfactant formula resulted in 28.46% and 49.96% improvement over conventional water flooding in a realistic pore–throat structure and idealized pore–throat network. The critical micelle concentration measurements of the mixture suggested favorable micelle formation, contributing to gel-like properties that improved sweep efficiency by lowering the mobility ratio. In heterogenous pore–throat networks, the emulsification, micellar solubilization, wettability alteration, and viscoelastic properties of the surfactant mixture favored the oil recovery process. This work provides experimental evidence and mechanistic insights for the application of viscoelastic surfactants in EOR in heterogeneous reservoirs. Full article

Manganese (Mn) oxides exhibit significant potential to either stabilize or destabilize soil organic carbon (SOC) through the polymerization and/or oxidation of organic molecules via organo-mineral interactions. Birnessite (MnO₂) is known to strongly interact with soil dissolved organic matter (DOM), which is DOM composition-dependent. Humic acid (HA) and fulvic acid (FA) are commonly used as organic fertilizers in soils. In this study, the contrasting reaction of DOM with birnessite in flooded paddy soil with HA and FA amendment was investigated at a molecular level. The results demonstrated that HA amendment enhanced the reaction of phenolic compounds in soil DOM with birnessite, leading to the formation of condensed aromatic compounds and polymeric products (PP) with higher molecular weights and aromaticity. This suggests that HA amendment enhances the birnessite-induced polymerization of soil DOM. In contrast, FA facilitated the birnessite-induced oxidation of soil DOM, yielding dicarboxylic acids (DA), monocarboxylic acids (MA), and quinones products (QP). These findings demonstrate that the reactivity of soil DOM with birnessite is significantly influenced by the composition of DOM exogenously added. This study provides comprehensive understandings of the interactions among Mn and C and helps to predict behaviors of DOM molecules in flooded paddy soil, which is critical for optimizing sustainable soil management. Full article

Levee failures caused by prolonged flooding and elevated upstream water levels pose a significant risk to floodplain communities, especially as the number of extreme hydrological events increases under climate change. Understanding seepage-induced weakening and failure mechanisms is essential for improving levee design and resilience. This study develops a numerical framework that integrates unsaturated and saturated seepage analysis with slope stability evaluation to simulate seepage front progression and predict failure initiation. The model employs van Genuchten-based soil water retention properties and experimentally derived hydraulic conductivities, with results validated against five experimental cases with varying hydraulic conductivity contrasts between the levee body and foundation soils. The simulations reproduced seepage front evolution and slope deformation patterns with good agreement with experimental observations. In cases with high permeability contrasts, the model captured foundation-dominant seepage behavior, while moderate- and low-contrast scenarios showed close alignment with observed phreatic line development. Slight deviations were noted in failure timing, but the framework demonstrated potential for reproducing seepage-induced instability in levees. The findings contribute to understanding how the internal soil composition governs levee performance under flooding and provide a basis for developing seepage countermeasures and early warning tools. This approach offers practical value for risk-informed levee design and flood management. Full article

The growth of urban areas and climate change affect the performance of water management, increasing the rate of flooding and decreasing the quality of available water. To address this issue, the sustainable urban drainage systems (SUDs) and conventional urban drainage systems (UDIs) must be promoted. In both systems, grey infrastructure plays an important role, in the form of reinforced concrete tanks, filters, and water treatment plants. Nowadays, the use of reinforced concrete is a major contributor of the environmental impact of human activities environmental impacts. This study aims to assess the potential of nanoparticle-based concrete to mitigate the environmental impacts of water management facilities. To achieve this target, a comparative Life Cycle Assessment (LCA) analysis was performed on a multi walled carbon nanotubes (MWCNTs) based concrete, and a conventional one. To evaluate the corresponding benefits, a Functional Unit has been defined representing a frequently used element in water management facilities. The conducted review found no similar research. It is noted that the functional units used in published studies on nanoproducts are usually defined for the production of mass units. This study, found that using MWCNT-based concrete reduced the weight of the steel reinforcement by 47%. This reduction in steel outweighs the environmental impacts corresponding to used MWCNTs. The impact scores obtained are significantly lower for the MWCNT-based concrete. Therefore, the use of this material is recommended in Water management facilities, only on an environmental basis. Further investigation is recommended into the economic viability of this use. Full article