Search Results (482)

Long-term shoreline change on tropical islands is spatially heterogeneous, but alongshore contrasts remain insufficiently resolved. We quantified shoreline change along the 151.1 km eastern sandy coast of Hainan Island, China, from 1987 to 2025 using Landsat-derived visually interpreted shoreline proxies and the Digital Shoreline Analysis System across 1413 transects. The coast was broadly stable to accretional, with a mean linear regression rate (LRR) of 0.49 m/yr and a mean net shoreline movement (NSM) of 17.72 m. Under the uncertainty-aware classification, 28.0% of transects were stable, 42.1% accretional, 8.2% erosional, and 21.7% indeterminate. For descriptive comparison, the eight sectors were grouped into three broad alongshore zones: a stable northern zone (Beaches A–B), an accretion-dominated central zone (Beaches C–E), and a heterogeneous southern zone (Beaches F–H). The strongest accretion occurred at Beach D (LRR = 7.63 m/yr), whereas the strongest erosion occurred south of the offshore artificial island at Beach F (LRR = −3.97 m/yr). These contrasts show that coast-wide stability or accretion can mask localized erosion. The observed patterns were spatially associated with differences in headland-bay morphology, nearshore seagrass beds, engineering structures, estuarine processes, and lagoon-inlet settings. The findings support beach-sector monitoring and differentiated coastal management. Full article

Coastal erosion is commonly assessed from shoreline-position change using methods such as the Digital Shoreline Analysis System (DSAS). However, on microtidal sandy beaches with strong seasonal wave variability, shoreline retreat may reflect temporary sediment redistribution rather than permanent erosion. This study evaluates the morphodynamic behaviour of a ~280 km sandy coastline along the Mexican Caribbean (Isla Blanca–Punta Allen) between 2009 and 2024 using high-resolution RapidEye and PlanetScope satellite imagery. Beach-area changes were quantified for 160 sedimentary cells and analysed with the Mann–Kendall test to identify long-term morphological trends, while shoreline mobility was assessed separately using the DSAS End Point Rate (EPR) and Linear Regression Rate (LRR). The results indicate that the coastline is predominantly characterised by dynamic equilibrium and seasonal sediment redistribution: 64.4% of the cells remained stable, 15.0% exhibited redistributive behaviour, and only 12.5% showed persistent beach-area loss. In contrast, the DSAS analysis based on Total EPR showed shoreline retreat (EPR < 0) in 78.1% of the cells, whereas only 12.5% showed persistent beach-area loss, indicating that shoreline-position change alone may overestimate chronic erosion along this seasonally dynamic coast. Although DSAS rates were moderately to strongly correlated with beach-area trends (r = 0.59–0.64), the two approaches led to markedly different management interpretations. These findings demonstrate that multi-temporal beach-area analysis provides a valuable complement to shoreline-based methods, enabling a clearer distinction between seasonal variability and chronic erosion on highly dynamic microtidal coasts. Full article

Satellite imagery has helped to provide decades of shoreline change data to coastal regions all over the world. Although shorelines around the globe have been armored with different types of coastal structures to try and protect beaches and properties from erosion, there are few studies of shoreline dynamics within structures such as groin fields using satellite images. Here we apply satellite-derived shoreline techniques to three areas of California: Ventura, Santa Monica, and Newport Beach, each site containing groin fields of varying number and length. Shoreline trends during 1984–2022 reveal that the presence of these coastal structures may alter the overall shoreline variability at these locations. Peclet numbers have been calculated for each site to better characterize the variability of longshore transport within and across the study areas and to compare with shoreline change characteristics. The satellite-derived shoreline data reveal offsets or “steps” in the shoreline position across the groins with sediment pilling up on one side more than the other due to longshore transport. The magnitudes and dynamics of these shoreline offsets were measured from satellite techniques, and we find that the average offsets are commonly related to groin length. Some shoreline offsets reveal seasonal patterns, with Newport Beach having the largest seasonal patterns of the three sites. We find that these seasonal patterns in shoreline offsets at the Newport Beach groins are related to the seasonal variability in wave direction and littoral transport. We conclude that satellite-derived shoreline techniques with Landsat and Sentinel-2 imagery are adequate to characterize shoreline behaviors within the complex coastal settings of groin fields. Full article

Most studies of sandy shoreline forecasting address relatively short time scales. Under limited annual observations and strong shoreline persistence, the added value of a Transformer over simple baselines and the influence of remotely sensed shoreline definitions remain insufficiently tested. Using Xichong Beach, Shenzhen, we constructed 40-year shoreline series for 80 transects from 284 quality-controlled Landsat waterlines acquired during 1986–2025. We compared a quality-controlled annual landward-envelope composite waterline with annual median waterlines and examined the effects of transect spacing and positional error on long-term change rates. We then developed a residual spatiotemporal Transformer that uses 10 years of shoreline states and historical wind–wave exposure to directly predict five future horizons, and compared it with persistence, rolling linear trend, and random forest models. The annual landward-envelope composite waterline was systematically landward of the annual median waterline (positional RMSE, 12.78 m), but their alongshore LRR patterns were strongly correlated (r = 0.982) and identified consistent major erosion–accretion zones. After Monte Carlo error propagation, the beach-mean LRR was −0.250 m yr⁻¹ (95% interval, −0.299 to −0.203 m yr⁻¹), whereas the direction of change remained uncertain at 39 local transects. Across 400 year–transect locations in the independent 2021–2025 evaluation period, the Transformer produced the lowest RMSE, MAE, and Dynamic RMSE (9.403, 7.399, and 12.042 m, respectively), with an RMSE skill of 27.0% relative to persistence. Environmental features yielded a small gain during rolling validation but no stable improvement in the independent evaluation period. SHAP attribution identified recent shoreline state as the dominant predictive information, followed by wind–wave exposure. Direct forecasts for 2026–2030 gave a beach-mean displacement of −8.527 m in 2030 (95% conditional residual bootstrap interval, −12.514 to −4.950 m), although every local-transect interval crossed zero. Multi-year predictability is therefore scale dependent: beach-mean trends are more resolvable, whereas local change directions remain constrained by observation error and model residuals. Full article

Beach nourishment has become one of the principal soft-engineering strategies for mitigating coastal erosion while preserving the recreational, environmental and protective functions of sandy beaches. During the last four decades, Spain has accumulated extensive experience in beach nourishment, with annual nourishment volumes approaching 10 million m³ under a wide range of coastal settings. Many of the best-documented engineering examples originate from the Gulf of Cadiz, although the lessons synthesized here are interpreted within the broader context of Spanish coastal practice. This structured narrative review combines publications retrieved from Web of Science and Google Scholar with Spanish technical reports, project records, and institutional sources. It focuses on borrow-area characterization, sediment compatibility, construction quality control, post-nourishment monitoring, and adaptive management. Rather than providing a chronological description of nourishment projects, this review examines how repeated project implementation, monitoring and maintenance have progressively reduced uncertainty and improved engineering practice. Long-term nourishment performance is controlled more by sediment compatibility, local morphodynamics, and construction quality than by the total sediment volume placed. It also demonstrates that systematic monitoring provides the feedback required to improve future project design, optimize maintenance strategies and support evidence-based coastal management. The principal contribution of four decades of Spanish beach nourishment has been the progressive development of an engineering framework in which quality control, long-term monitoring and accumulated field experience continuously refine project planning and management. Although derived from Spanish practice, the lessons synthesized are broadly applicable to nourishment programs facing increasing pressures from climate change, sediment scarcity and growing environmental constraints. Full article

This paper addresses the geomorphic response of an engineered Chicago beach to a >1.5 m rise in Lake Michigan’s base water level, from 2013 to 2020. Topographic monitoring data acquired since 2012 and subsurface geophysical data collected in 2022 are integrated to explore the roles of lakefront infrastructure and beach topographic development on sedimentary dynamics, beach morphologic development, and stratigraphic architecture. While conceptual models of coastal geomorphology infer upward and landward beach-profile translation with lake-level rise, a high degree of along-shore variance occurs within pocket beaches. This stems from infrastructure-related modifications of storm hydrodynamics and scour patterns, close to shore, and backshore terrain physiography. The studied beach evolved contrary to how regional littoral drift patterns would have suggested, with erosion most severe along the embayment’s downdrift end, a product of infrastructure-induced scour and the reduced capacity for sediment retention through overwash accretion. Documented geomorphic patterns with lake-level rise are manifested in subsurface imaging data from the lake-level highstand, accordingly, providing a guide to more regional paleo-reconstruction. Great Lakes urban pocket beaches buffer shoreline infrastructure, offer recreational terrains, and support dune ecosystems of value to migrating shorebirds. Understanding their geomorphology benefits coastal managers looking to mitigate impacts of future climate and lake-level change. Full article

Sicily is a Mediterranean island region whose economy is based especially on tourism, with tourists being attracted to its beaches. The whole coastline of the island, including its minor islands, is 1745 km. At the moment, considering the whole period analyzed by the Coastal Plan of Sicilian Region (2008–2024), about 115 km of the 683 km of the main island’s sandy coastline present erosion problems that affect 23% of its unprotected coastline (506 km). Some of these problems are threatening Sicily’s economic and important historical assets as well as its cultural heritage; 177 km of protected beaches, using hard structure, have lost their original beauty. In the last fifty years, about 2.5 km² of beaches were lost due to erosion, causing damages worth approximately 5 billion Euros. Current coastal management guidelines identify artificial beach nourishment as the most sustainable strategy for protecting the insular economy against the accelerating impacts of climate change. Successful nourishment, however, hinges on the availability of vast quantities of borrow material that must be granulometrically, compositionally, and chromatically compatible with native beach sediments. While subaerial quarries are being phased out due to their irreversible environmental degradation and logistical inefficiency, as well as local “ephemeral” sources (such as harbor dredging or over-alluvial deposits) providing insufficient volumes, the research has shifted toward Remote/Relict Marine Sediment Deposits (RMSDs). This study evaluates the strategic potential of RMSDs as a high-volume, low-impact resource for coastal defense. By integrating the geological, morphological, and sedimentological characteristics of the Sicilian continental shelf within a GIS framework, we have delineated potential dredging sectors. These areas are bounded by the −30 m isobath (the lower limit of Posidonia oceanica meadows) and the −200 m isobath, which represents the current operational limit of Jumbo Trailer Suction Hopper Dredgers (TSHDs). A multi-criteria constraint analysis was performed, categorizing environmental and infrastructural overlaps into fatal flaws (prohibitive) and non-prohibitive constraints. This subtractive spatial analysis reveals that approximately 6500 km² of the Sicilian shelf may be eligible for resource exploitation concessions, pending site-specific, high-resolution surveys. Full article

Coastal zones are facing rising exposure to climate-related hazards alongside intensifying human pressures, which highlights the need for robust tools to assess vulnerability. This study uses a GIS-based Coastal Vulnerability Index (CVI) to quantify and map relative vulnerability along ~13 km of shoreline in Al Hoceima Bay (northern Morocco). The proposed CVI integrates eight geological and physical indicators, including geomorphology, shoreline erosion and accretion rates, coastal slope, elevation, natural habitats, relative sea-level rise, significant wave height, and tidal range. Spatial analyses were performed using remote sensing data, historical records, field measurements, and Geographic Information Systems (GIS). The analysis reveals that 37% of the shoreline is categorized as high vulnerability, 44% is moderate, and 19% is low. Highly vulnerable sectors are primarily associated with low elevations, gentle coastal slopes, sandy beach systems, limited natural habitat protection, and proximity to river mouths. These findings demonstrate that the applied CVI provides a rapid and cost-effective framework for identifying priority areas for coastal management and climate adaptation. The proposed approach offers valuable decision-support insights for sustainable coastal planning in Al Hoceima Bay and other Mediterranean coastal environments characterized by limited data availability. Full article

Coastal zones are dynamic interfaces where land, ocean, and atmosphere interact, making them sensitive indicators of environmental change. However, quantifying shoreline movement across long distances and over multi-year timescales remains challenging using traditional ground-based methods alone. We conducted an analysis of environmental factors and shoreline dynamics along a 58 km stretch of the arid Cabo Pulmo shoreline in Mexico from 2020 to 2026 using the CoastSat tool. The landscape is characterized by a diverse array of geographical features, including sandy beaches, granite cliffs, estuarine systems, and various anthropogenic structures. Results indicated a sea-level rise of 2 mm/year over the last 27 years, which is consistent with the reported range for the Pacific (1.8 to 3.8 mm/year). Notably, we observed an increasing trend of Category 4 and 5 hurricanes in the Mexican Pacific, with an average of 1 additional hurricane per decade (1950–2023). A total of 457 Sentinel-2 satellite images were used for automated analysis using the CoastSat platform, all of which were acquired under tidal conditions not exceeding 1 m. Our findings indicate that the granite cliffs show no detectable horizontal changes in the satellite images; however, their minimal vertical erosion contributes sediment to adjacent beaches. The most significant shoreline erosion was observed north of a marina breakwater, measuring −19.7 m, attributed to the disruption of littoral transport toward the southeast. In contrast, sandy beaches located in front of streams and estuaries—characterized by a lack of infrastructure (houses and breakwaters) and gentle slopes of 2° to 4°—demonstrated positive accretion of up to 5.9 m. According to the autoregressive distributed lag model, wave energy and hurricane-driven wind gusts are the primary agents of shoreline retreat, displacing sediment seaward to the continental shelf. Sea level rise exacerbates this retreat, while rainfall plays a minor but contributing role by transporting sediment during hurricanes in this arid region. This study highlights the effectiveness of CoastSat as a neural network-based tool for analyzing shoreline changes; however, we faced certain limitations, such as the absence of in situ beach profiles due to restricted access. Full article

Sandy coastlines are dynamic geomorphological units supporting dense human populations and intensive economic activities. However, their evolution is increasingly dominated by anthropogenic modification rather than natural processes. This study investigates shoreline evolution along the western Liaodong Bay coast, China, where extensive anthropogenic engineering has potentially altered natural dynamics. A 30-year satellite-derived shoreline (SDS) analysis of 23 sandy beaches (Xingcheng–Suizhong, 1995–2024) was conducted using the CoastSeg framework and DSAS statistical methods across three sub-periods (1995–2005, 2005–2015, 2015–2024). Shoreline change rates ranged from −1.35 to +2.12 m/yr; 11 beaches (47.8%) exhibited net erosion and 12 (52.2%) net accretion or stability, with marked spatial heterogeneity within individual beaches. This complex spatio-temporal pattern shows the strongest spatial correspondence with the non-uniform distribution of anthropogenic structures—including ports, breakwaters, and land reclamation—which generate an “engineering proximity effect” that may fragment natural beach continuity and contribute to a regional alternating erosion–accretion mosaic pattern, though direct mechanistic verification awaits future hydrodynamic modeling. Shoreline evolution along the western Liaodong Bay coast has entered a stage of “multi-layered anthropogenic control,” requiring frameworks that integrate multi-scale, multi-process coupling mechanisms and transcend traditional regional-averaging approaches. These findings provide critical insights for spatially differentiated management of engineering-intensive sandy coasts. Full article

The intertidal beach profile provides a fundamental representation of beach morphology and serves as a key indicator of shoreline morphodynamics. To enable frequent and accurate mapping of intertidal beach profiles, this study proposes an automated reconstruction framework that integrates single-pixel image columns with a stacked bidirectional long short-term memory (Bi-LSTM) network. Time-exposure imagery, commonly referred to as Timex imagery, acquired from a shore-based video monitoring station at Xisha Bay, China, is used as the primary data source, while wave records obtained from a wave buoy are incorporated to assign elevations to the detected waterline breakpoints, thereby enabling automatic beach profile reconstruction. The stacked Bi-LSTM network is trained for land–sea segmentation and waterline breakpoint localization. achieving the best performance among the tested methods, with precision, recall, accuracy, and F1 score values of 0.951, 0.894, 0.978, and 0.903, respectively, and a mean breakpoint localization error of 2.23 pixels. Breakpoint elevations were then estimated using a local slope–wave setup attribution model. Validation against field-measured topographic data from four fixed profiles and three survey periods showed good agreement between the reconstructed and measured profiles, with a period-based root mean square error (RMSE) of 0.212 ± 0.080 m. When all validation points were combined, the reconstructed elevations showed strong agreement with the measured elevations, with a coefficient of determination (R²) of 0.988 and an overall RMSE of 0.24 m. The profile comparisons further showed that the reconstructed profiles generally captured the overall profile shape and cross-shore morphological pattern of the measured profiles, although reconstruction accuracy varied among the four fixed profiles. These differences demonstrate that camera viewing angle, field-of-view position, camera-to-profile distance, and image quality are important factors influencing video-derived beach profile reconstruction. These results indicate that the proposed method can directly reconstruct fixed intertidal beach profiles from shore-based Timex imagery without generating a digital elevation model of the entire intertidal zone. It provides a practical tool for high-frequency monitoring of intertidal profile morphology and supports the quantitative analysis of beach erosion–accretion dynamics. Full article

Beach nourishment, as one of the most widely and effectively used coastal management measures recently, inevitably changes the coastal environment. This study aims to assess how the coastal profile is transformed during repeated beach nourishments with coarser-than-native sand in the Palanga recreational zone, Lithuania, Baltic Sea, using field survey data from the last three decades. When the granulometric composition of the sand is artificially changed during nourishment, the beach adapts to environmental changes by adjusting its morphometric parameters. These changes can be perceived as an intensification of coastal erosion, and, at the same time, a failure of the project. However, the results of this study show that these changes are associated with the transformation of the beach towards a morphologically adjusted state under the new sediment characteristics. In the Palanga case, the coarser-than-native sand used for nourishment led to narrower and steeper beaches compared to the pre-nourishment beaches composed of finer sand, and these characteristics persisted five years after nourishment. Therefore, the wide and low-slope beaches created during beach nourishment could not maintain the formed morphometric features with the coarser sand. For this reason, when implementing a replenishment project, it is important to predict the cross-shore profile that will develop for a given grain-size composition and quantity of the nourishment sand. Full article

Nourishment grain size is a key parameter in beach nourishment projects, directly determining beach stability under extreme hydrodynamic environments. Taking Xiaoshizui Beach on Wailingding Island as the study area, this paper establishes a coupled typhoon storm surge–wave–sediment model based on the MIKE 21 HD-SW-ST coupled model. This model has been systematically verified through the measured data of tide levels, waves, and beach profiles, and the verification results are satisfactory. Four scenarios with nourishment grain sizes of 0.4, 0.6, 0.8, and 1.0 mm were established to quantify the morphological evolution patterns of the beach under strong typhoons. The results indicate that during the typhoon, the beach exhibits a cross-shore sediment transport pattern characterized by erosion of the backshore dune, accretion of the upper-middle foreshore, and erosion of the lower foreshore. The influence of nourishment grain size shows significant spatial variability: increasing grain size enhances the erosion resistance of the backshore and berm, reducing the erosion extent; however, within the breaker zone, coarse sand tends to form a steep profile, intensifying wave breaking, which increases the scour depth in this region. This study elucidates the regulatory mechanism of grain size under extreme conditions, providing scientific reference for grain size selection in beach restoration projects. Full article

Tam Quan Inlet, a monsoon-driven asymmetric entrance on the south-central coast of Vietnam, has experienced persistent shoaling and severe downdrift erosion despite jetty construction and repeated maintenance dredging. This study investigates the unresolved linkage between seasonal circulation reorganization, inlet-directed sediment convergence, channel infilling, and southern-beach erosion. A coupled Delft3D-FLOW/WAVE model, constrained by field observations from May 2022 and November–December 2022, was used to diagnose hydrodynamic controls and compare alternative management layouts. The model satisfactorily reproduced the dominant variability of water level, wave conditions, and depth-averaged currents during calibration and independent validation, providing a suitable basis for process diagnosis and comparative layout assessment. The simulations identify four recurrent circulation modes: a cape-crossing north-to-south longshore jet, flow acceleration and deflection near the southern jetty, a northeast-monsoon recirculation cell that promotes inlet-directed convergence from the southern beach, and a partial summer reversal under SE-sector waves. These modes explain why shoaling persists after one-sided intervention and why the southern shoreline functions simultaneously as an eroding downdrift beach and a seasonal sediment source to the inlet. Among the tested layouts, PA2 most effectively concentrates flow through the inner throat while relocating sediment retention to an external storage basin, supporting controlled trapping and periodic bypassing. The results support a sediment-balanced management strategy that integrates controlled trapping, maintenance dredging, and sediment bypassing to improve navigation reliability and reduce the sediment deficit along the downdrift shoreline. Full article

This study presents the first fine-scale Coastal Vulnerability Index (CVI) assessment for Togo, evaluating coastal vulnerability and risk along the country’s 50 km barrier coastline in the context of accelerating erosion, rising sea level, and growing human exposure. Using remote sensing, GIS, and a CVI framework, shoreline trend rates, beach width, land use, and the role of existing coastal defences were analysed to support risk-informed decision-making. The coastline was segmented into 99 coastal units of 500 m, and shoreline trend rates were computed using the End Point Rate (EPR) method based on multi-temporal satellite-derived shorelines spanning from 1988 to 2024. Results show strong spatial contrasts in vulnerability, with the eastern sector of the Port of Lomé, particularly a 24.5 km stretch, exhibiting high vulnerability due to persistent shoreline retreat and narrow beach widths. In contrast, the western coastline displays lower vulnerability levels. Several erosion hotspots were identified, including Baguida and Dévinkemé, where recent shoreline retreat reaches up to −12.8 m/year. Existing coastal defences locally mitigate erosion impacts, reducing the extent of highly vulnerable shoreline from 23.5 km to 15 km. The integrated risk assessment identifies 6.5 km of coastline, primarily in the eastern port area, as being at high risk due to the combined effects of erosion and dense human settlement. These results provide spatially explicit information to support integrated coastal zone management, land-use planning, and adaptation strategies in Togo. Full article