Orals: Wed, 6 May, 08:30–12:15 | Room -2.20
Humans are depositing ever-increasing volumes of sediment on the Earth’s surface, much of this in coastal areas. In this contribution we show how some of this artificial sediment is rapidly changing into rock on interaction with coastal and marine processes, and creating new anthropogenic rock coasts. At a case study site in West Cumbria, UK, ferrous slag (a by-product from iron and a steel making) was deposited from ~1860 to 1980 at the coast, forming a bank ~2.5 kilometres long and up to 30 metres high. Over time, wave action from the Irish Sea has eroded the seaward side of this slag bank releasing material onto the foreshore. This material has been reworked by wave and tidal processes, and then deposited on the foreshore, before subsequently undergoing rapid lithification. The present-day foreshore is thus made of a rock platform composed largely of this eroded slag – an anthropogenic rock coast.
The rock platform is a form of conglomerate, with clast analysis showing that the clasts of slag are dominantly sub-rounded to rounded. Scanning Electron Microscopy analysis revealed the slag clasts are cemented together with calcite mineral cements, and occasional other minerals such as goethite. The highly chemically reactive nature and high calcium concentration of the slag resulted in leaching of calcium, making interclast porewaters hyperalkaline, resulting in ingassing of CO2 and precipitation of the dominant calcite cement. Prior to slag dumping, this coastline was a soft coast. Industrial activity, and human deposition of anthropogenic geomaterials, can be shown to dramatically change the physical and hydrodynamic properties of the coast, resulting in the rapid change from a soft coast to a rock coast at the case study site.
How to cite: MacDonald, J. M., Owen, A., and Brown, D. J.: Formation Mechanisms of Anthropogenic Rock Coasts, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1386, https://doi.org/10.5194/egusphere-egu26-1386, 2026.
Bedrock cliffs act as natural barriers against coastal hazards such as storm surges, flooding, extreme waves and runup; but they can fail due to hydrodynamic forcing and weathering. Rockfalls and landslides from eroding cliffs represent a significant, yet understudied hazard to humans and infrastructure. Understanding the complex dynamics of cliff erosion is essential for assessing and mitigating coastal hazards, especially in the context of climate change and sea-level rise, which are expected to change the hydrodynamic load and accelerate cliff retreat.
In Ireland, approximately 56 % of its extensive rocky coastline is rock-dominated. Despite this, rates and mechanisms of rock-cliff recession remain poorly quantified and understood and lag far behind those of soft coasts. This is partially due to difficulties associated with accessing hazardous coastal cliffs. Recent advances in Interferometric Synthetic Aperture Radar (InSAR) provide an opportunity to overcome these limitations by enabling millimetre-scale deformation monitoring over large and inaccessible areas.
In this study, Persistent Scatterer InSAR (PS-InSAR) was applied to assess long-term coastal cliff deformation along the west coast of Ireland. The aim of the study was to test the utility of PS InSAR as an approach for detecting and measuring rock coast erosion. Two areas of interest (AOIs) were analysed: AOI-1 (20 km, from Doonbeg to Murrooghtoohy North) and AOI-2 (14 km, from Doonbeg to near Kilbaha). A total of 100 Sentinel-1 VV-polarised Single Look Complex (SLC) images were processed for each AOI, spanning from August 2016 to December 2024. Data preparation was carried out using the SNAP2StaMPS workflow, and PS-InSAR processing was performed using the StaMPS algorithm in MATLAB.
The results indicated that both AOIs have remained largely stable over the eight-year period, with maximum cumulative Line-of-Sight (LOS) displacements of –11 mm in AOI-1 and –15 mm in AOI-2. Despite this overall stability, localised clusters of LOS displacement were identified, particularly around Breaffa South, Co. Clare, suggesting ongoing cliff retreat. Active Deformation Area (ADA) analysis, based on a velocity-threshold approach, revealed that active deformation is not randomly distributed but is concentrated mainly in the southern part of the study area. Active PS points predominantly occur on sandstone, siltstone, and mudstone, whereas stable PS points are more commonly associated with mechanically stronger lithologies such as limestone, dolomite, and cherty units. An assessment of terrain geometry further demonstrated a strong dependence of PS detectability on slope, with breakpoint analysis identifying a critical threshold at approximately 21°, beyond which PS generation begins to decrease noticeably.
The PS InSAR results were validated using a high-resolution topographic data derived from drone and Bland–Altman analysis. The analysis revealed a systematic positive bias of 1.02 mm, indicating that PS-InSAR slightly underestimates displacement. Limitations such as layover, coverage gaps, and reduced sensitivity to rapid deformation were identified to affect the application of PS InSAR. Overall, the findings demonstrated that PS-InSAR is an effective tool for identifying zones of cliff instability, identifying ground displacement over large areas, long-term monitoring and good use as a first step, but must be combined with traditional methodologies.
How to cite: Essel, B., D. Cullen, N., C. Bourke, M., Cox, R., and Loureiro, C.: QUANTIFYING RATES OF ROCK CLIFF EROSION USING PS InSAR TECHNIQUE, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2822, https://doi.org/10.5194/egusphere-egu26-2822, 2026.
More than half of the Irish Coast can be considered rocky, featuring cliffs and shore platforms in various environments and comprising different lithologies. In the face of climate and sea-level change, cliff retreat and its drivers had become an important research subject. For investigating coastal changes on millennial scales, modelling maximum likelihoods of possible exposure histories of shore platforms based on beryllium-10 (10Be) concentrations have become regularly used in the past decade. We applied 10Be analysis at four sites along Ireland’s west coast to study the interaction between local environment, changes in relative sea level (RSL) and climate, and cliff retreat. Our preliminary results indicate decreasing erosion rates during the Holocene, with till cliffs and hard rock cliffs retreating a few centimetres and millimetres annually, respectively. Depending on factors such as lithology, local RSL change, and exposure to the North Atlantic, initial retreat rates at each site were as much as one order of magnitude higher. While Sandstone cliffs show initial erosion rates of 12–14 mm*year-1, glacial cliffs initially retreated with several centimetres per year, reaching rates to 10 cm*year-1, even when located in inner bay settings. Some sites, especially those featuring cliffs of glacial sediments, show indications for pre-Holocene shore platforms. Cliffs attached to pre-Holocene shore platforms experienced an initial increasing retreat rate, accompanied by high rates of Holocene RSL rising, followed by a decreasing retreat rate. Our findings indicate that slower rates of RSL change lead to decreasing cliff retreat rates. Some previous studies on rocky coast erosion around the world have found similar relationships between changes of RSL and cliff retreat rates, while others could not detect any connections. These differences show a potential influence of variations in regional local coast and environmental settings.
The much lower recent cliff retreat rates raising the question of whether retreat of certain cliff configurations has shifted from marine-driven erosion towards more terrestrially driven erosion, and, if so, whether we might anticipate a shift back towards marine forcing as global sea-level rise accelerates.
How to cite: Rink, G. M., Bromley, G. R. M., and Hall, B. L.: Quantifying rates and identifying drivers of rocky cliff retreat along Ireland’s west coast, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7730, https://doi.org/10.5194/egusphere-egu26-7730, 2026.
Rocky coastlines of newly formed lava deltas change rapidly after their emplacement if they are exposed to energetic waves and where they are internally weak. Such rapid changes can be studied in detail using time-lapse remote sensing data from recent eruptions. Two lava deltas were created during the 2021 La Palma eruption. We use 0.5-m-resolution Pléiades satellite images to characterize their evolution on daily and monthly intervals over 14 months, providing young lava-coastline change data of high temporal resolution for the first time. Coasts of these two deltas are classified into pocket beaches and rock promontories. The pocket beaches were formed from eroded volcanic materials. Fluctuations in their positions correlate strongly with tidal water level. Within the first 39 days, annualised coastal retreat rates of the promontories reached 712 m/yr, the fastest retreat rates found so far in young lava coasts, before decreasing with time. We interpret this change as due to the presence of friable materials on the lava fronts (e.g., clinker), which were easily eroded by waves initially, in contrast with later slow retreat due to more resistant lithologies within lava flow interiors. Slowed coastal retreat may also be due to attenuation of waves crossing a growing submarine platform in front of the deltas and protection from clastic materials formed by collapsed sea cliffs. In addition, the coastline of the northern delta became more crenelated in plan-view and retreated quickly. That retreat followed a similar systematic slowing found in other new rocky coasts formed by historical eruptions. In contrast, coastline of the southerly delta was more rounded and changed minimally. These deltas experienced two markedly different histories despite lying less than ~1 km apart, which can be explained by different patterns of lava flow emplacement and internal structure.
How to cite: Zhao, Z., Mitchell, N. C., Rodríguez, J. A. L., Fraile-Nuez, E., Vázquez, J. T., Quartau, R., and Ramalho, R. S.: Rapid changes of the lava-delta coastlines formed by the 2021 volcanic eruption on La Palma, Canary Islands, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-132, https://doi.org/10.5194/egusphere-egu26-132, 2026.
Sandy coasts are among the most dynamic and vulnerable environments, yet the development of robust and scalable methods for shoreline extraction from satellite imagery remains under discussion. Most current approaches delineate shorelines at the pixel scale, so their accuracy is intrinsically constrained by sensor resolution and pixel geometry. In this contribution, we present an isoradiometric sub-pixel shoreline extraction method, operationally implemented via QGIS scripting and Google Earth Engine (GEE), to support coastal morphodynamics and landscape-evolution analyses over multi-decadal timescales. We first develop and test the method on three Sicilian sandy beaches (Torre Salsa, Balestrate, and Vendicari), combining field radiometric measurements with multi-sensor satellite data (Landsat-8, Sentinel-2, and Planetscopes). Radiometric profiles acquired across the water–sediment interface are used to define spectral profiles and an iso-reflectance line at bottom-of-atmosphere associated with the shoreline, with particular emphasis on red-edge, near-infrared, and shortwaves bands. These iso-radiometric lines are then interpolated across the satellite scenes to obtain a continuous, sub-pixel shoreline. Independent NRTK GNSS surveys collected along the swash zone are used to validate the extracted shorelines and to quantify positional accuracy. Our results show that the isoradiometric approach on near infrared (NIR) bands can achieve shoreline position accuracy comparable to, and in several cases exceeding, those of more complex state-of-the-art methods, while remaining conceptually simple and cost-effective. The analysis of method performance across sensors highlights the key role of NIR bands and allows us to discuss the trade-offs between spatial and temporal resolution. We also systematically assess critical factors that can bias shoreline position, such as breaking waves, beached Posidonia oceanica, cloud and terrain shadows, and water-body radiometric effects, providing practical guidance to minimize their impact. In a second step, we iteratively apply the method to multi-decadal satellite image series, as well as seasonal datasets, to quantify long-term shoreline change and to distinguish phases of regression and transgression. The resulting time series are integrated into a simple quantitative landscape-evolution framework, enabling the estimation of differential erosion and accretion along the coast. Finally, we implement the full workflow in an open and reproducible way by combining GEE for large-scale image access and pre-processing with QGIS models and Python scripting for shoreline extraction and analysis. This integrated environment allows non-expert users and decision-makers to apply the isoradiometric method at a regional scale, thus offering a practical tool to support coastal erosion assessment and adaptation planning in the context of ongoing and projected climate-driven changes.
How to cite: Balsamo, L., Caldareri, F., Parrino, N., Ponte, E., Dardanelli, G., Todaro, S., Maltese, A., and Sulli, A.: Shoreline Extraction from Earth Observation data using the Isoradiometric Method: a QGIS scripting and Google Earth Engine workflow supporting landscape-evolution analyses, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2004, https://doi.org/10.5194/egusphere-egu26-2004, 2026.
With rising sea levels and changes to storm regimes, tidal inundation and coastal erosion pose a significant threat to communities near the coast (Jones et al., 2008). Foredunes have been proposed as a nature-based solution to such threats due to their ability to protect coastal communities from overwash, recover from storm damage, and provide a range of ecosystem services (van Puijenbroek et al., 2017; Strypsteen et al., 2024). However, coastal dune change depends on complex feedback between sediment deposition, marine erosion, and vegetation growth (Maun, 2009), making dune change difficult to predict and limiting our understanding of coastal dunes as management options. The development of predictive, accurate, numerical models may permit land managers to reliably use coastal dunes as a nature-based solution to many threats facing coastal communities (van Westen et al., 2024). One such potential model is AeoLiS.
AeoLiS is a process-based model for simulating sediment transport and morphological evolution in supply-limited environments (Hoonhout & de Vries, 2016). The model has been validated against the sand engine nourishment project in the Netherlands (Hoonhout & de Vries, 2019), and a range of dune forms including barchan, parabolic and coastal embryo dunes (van Westen et al., 2024). The purpose of this research was to assess how accurately the AeoLiS model could replicate coastal dune change at a range of sites along the English coast, ranging from embryo dunes to established foredunes and varying in the degree of management. The results show that the AeoLiS model is capable of replicating coastal dune changes along two-dimensional transects at the English coast, accurately simulating both embryo and established foredune changes as well as dune changes following sand fence installation. The fact that this model is capable of replicating dune growth accurately suggests that it may be a powerful tool for land managers to predict future dune changes.
References:
Hoonhout, B. M., & de Vries, S. (2016). Aprocess-based modelforaeolian sediment transport andspatiotemporal varying sediment availability. Journal of Geophysical Research: Earth Surface, 121, https://doi.org/10.1002/2015JF003692.
Hoonhout, B., & de Vries, S. (2019). Simulating spatiotemporal aeolian sediment supply at a mega nourishment. Coastal Engineering, 145, 21-35. https://doi.org/10.1016/j.coastaleng.2018.12.007
Jones, M. L. M., Sowerby, A., Williams, D. L., & Jones, R. E. (2008). Factors controlling soil development in sand dunes: evidence from a coastal dune soil chronosequence. Plant and Soil, 307, 219-234. https://doi.org/10.1007/s11104-008-9601-9
Maun, M. A. (2009). The Biology of Coastal Sand Dunes. Oxford University Press. 10.1093/oso/9780198570356.001.0001
Strypsteen, G., Bonte, D., Taelman, C., Derijckere, J., & Rauwoens, P. (2024). Three years of morphological dune development after planting marram grass on a beach. Earth Surface Processes and Landforms, , https://doi.org/10.1002/esp.5870
van Puijenbroek , M. E. B., Limpens, J., de Groot, A. V., Riksen, M. J. P. M., Gleichman, M., van Dobben, H. F., & Berendse, F. (2017). Embryo dune development drivers: beach morphology, growing season precipitation, and storms. Earth Surface Processes and Landforms, 42, 1733-1744. https://doi.org/10.1002/esp.4144
van Westen, B., de Vries, S., Cohn, N., van Ijzendoorn, C., Strypsteen, G., & Hallin, C. (2024). AeoLiS: Numerical modelling of coastal dunes and aeolian landform development for real-world applications. Environmental Modelling and Software, 179(106093), https://doi.org/10.1016/j.envsoft.2024.106093
How to cite: Withers, M., Wilson, R., Smyth, T., and Fox, B.: Comparing measured and modelled foredune change at the English coast using AeoLiS., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3856, https://doi.org/10.5194/egusphere-egu26-3856, 2026.
Sediment mobility in mangrove–sandbar coupled systems plays a key role in the evolution of coastal ecosystems through interactions between sediment dynamics, hydrodynamic forcing, and vegetation. Here, we present an integrated assessment of the hydro-sedimentary processes controlling the dynamics of intertidal mangrove–sandbar systems in the tropical context of Mayotte (Indian Ocean). Short-term in situ monitoring of morphological changes was combined with seasonal hydrodynamic measurements to investigate the respective roles of intertidal sandbars and mangroves in modulating local hydrodynamic processes. Two pilot sites, Tsingoni and Bandrele, were investigated using high-precision GNSS-RTK surveys and drone-derived digital elevation models (DEMs) to quantify sandbar morphology and volumetric sediment budgets, combined with hydrodynamic measurements from two acoustic Doppler current profilers (ADCPs) and eight RBR pressure sensors to characterize coastal morphodynamic processes. Results reveal contrasting dynamics between the two sites. At Tsingoni, intertidal sandbars exhibit rapid landward migration (10–61 m in 5 months) and significant vertical accretion (0.2–0.5 m), locally affecting young mangrove stands through sediment burial. In contrast, Bandrele shows more limited morphological changes, with minor sandbar migration and adjustment (0.2–0.3 m) at the mangrove edge at the mangrove edge and in adjacent troughs. Hydrodynamic analyses further indicate that under wave heights of ~0.68 m and current velocities of ~0.5 m s⁻¹, sandbars dissipate approximately 30% of the incident energy, while mangroves provide an additional 60–95% attenuation. Together, these results highlight the dynamic and complementary roles of sandbars and mangroves in shaping the evolution of tropical intertidal coastal systems.
Keywords: Mangrove, Intertidal sandbar, Sediment mobility, Morphodynamics, Coastal resilience, Hydro-sedimentary processes
How to cite: Erraji Chahid, N., Jeanson, M., Aubry, A., and Granjou, A.: Hydro-Sedimentary Dynamics and Morphological Evolution of Intertidal Sandbar–Mangrove Systems in Mayotte, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4973, https://doi.org/10.5194/egusphere-egu26-4973, 2026.
This study addresses the need to identify and characterize dynamic zones within coastal environments by examining the spatiotemporal variability of Total Suspended Solids (TSS MODIS), land surface state dynamics derived from the Relative Change Vector Maximum (RCVMAX), and sea level anomaly (SLA) within a barrier island system. The analysis focuses on the barrier island system of Cigu District, southwestern Taiwan, using a dataset spanning from 1 January 2015 to 30 June 2025. The study area encompasses the barrier sandbar and lagoon-facing coastal environment, extending approximately from 23.10° to 23.17° N and from 120.05° to 120.10° E, including ocean-exposed shorelines, tidal inlets, and internal lagoonal environments. Dynamic zones were delineated by quantifying day-to-day absolute changes in each variable at the grid level across more than nine million grid cells. High-change thresholds were defined using the 90th percentile, based on daily variability for SLA and annual variability for TSS MODIS and RCVMAX, enabling the identification of short-term extreme dynamics. SLA exhibits a continuous spatial pattern aligned with the main axis of the barrier island, reflecting coherent hydrodynamic forcing along the ocean-facing coast that is expected to intensify under projected sea level rise scenarios. TSS MODIS variability is spatially clustered, with pronounced changes in lagoonal waters, tidal channels, and nearshore embayments, indicating localized sediment resuspension and redistribution processes that are sensitive to changes in storm frequency, wave climate, and hydrodynamic energy. RCVMAX-derived dynamic zones capture temporal surface condition transitions rather than permanent land conversion, reflecting shifts between wet and dry states and between vegetated and non-vegetated surfaces driven by tidal inundation, exposure, and vegetation phenology that may be altered by climate-driven changes in inundation regimes and coastal ecological dynamics. Quantitatively, 258,524 high-change events were identified for TSS MODIS (≥ 0.00025), 249,133 for RCVMAX (≥ 1.009), and 333,904 for SLA (≥ 0.0349 m). All dynamic zone records were archived as individual CSV datasets. By mapping areas of recurrent short-term variability, the results provide a spatially explicit foundation for anticipating barrier island responses to future climate change, supporting adaptive coastal management, nature-based solutions, and long-term planning strategies.
How to cite: Lin, T.-Y. and Trihatmoko, E.: Spatiotemporal Delineation and Visualization of Coastal Environmental Dynamic Zones: A Case Study of TSS Modis, RCVMAX, and Sea Level Anomaly Variability in the Barrier Island of Cigu District, Taiwan, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6217, https://doi.org/10.5194/egusphere-egu26-6217, 2026.
In many coastal and estuarial areas, large-scale continuous submarine sandbars have been measured in the past few decades. Besides, strong tidal, nearshore, or runoff currents also exist in these regions. Due to the co-existence of free-surface water waves, ambient flow, and rippled seabed morphology, the hydrodynamic characteristics, especially the interaction effects among these elements, are very complex. Previously, the interactions above were usually studied separately in coastal hydrodynamics, i.e., Bragg resonance between water waves and rippled bottoms, as well as the wave-current interaction.
If we consider wave-current-bottom interactions from the perspective of wave hydrodynamics, the rippled seabed morphology could alter the wave-current interaction behaviors and even induce intensive resonant interactions among free surface waves, ambient currents, and rippled topography. The corresponding free-surface wave field and the flow field under the free surface will be affected if these intense resonances are triggered.
As one specific phenomenon, the upstream-propagating waves were observed in flume experiments for steady free-surface flow over rippled bottoms. The study for this specific wave component provides new insights into wave-current-bottom resonant interaction. We have performed a series of flume experiments, in which the different flow depths and flow velocities were adjusted above the rippled topography. Under a specific range of flow conditions, the new free-surface wave components are induced to propagate upstream continuously.
This specific resonance-induced hydrodynamic phenomenon could also be induced in estuarial areas, potentially. With the existence of rippled seabed morphology and tidal/runoff currents, this kind of wave stimulation might affect the wave field if it is triggered. However, the generation of this new wave component on the free surface not only depends on the resonant condition but also relies on some specific critical conditions (i.e., the critical flow velocity of wave energy stagnation for upstream-propagating waves).
In this study, based on the parameters of continuous submarine sandbars, flow velocity, and water depth conditions in typical estuarial and coastal areas, the potential conditions and parameter range for triggering the new free-surface wave components are calculated and evaluated for various resonant combinations for steady flow over rippled bottoms. The associated critical flow conditions underlying the resonant conditions are also discussed, along with the temporal evolution and spatial distribution behaviors of the resonant free-surface wave components involved or induced.
How to cite: Fan, J., Tao, A., Xie, S., Wu, C., and Zheng, J.: Hydrodynamic response induced by free-surface flow over rippled seabed morphology in coastal regions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12376, https://doi.org/10.5194/egusphere-egu26-12376, 2026.
Salt marsh vegetation plays a critical role in regulating hydrodynamics, sediment transport, and eco-geomorphic evolution in coastal wetlands. While biomass–elevation relationships have been widely investigated in temporal frameworks, the spatial organization of biomass across marsh platforms and its local geomorphic controls remain insufficiently understood.
In this study, we investigate the spatial distribution patterns of aboveground biomass of Spartina alterniflora across two salt marshes along the central Jiangsu coast, China. By combining multi-year satellite remote sensing data processed on Google Earth Engine with field-based vegetation sampling and surface elevation measurements, we quantify biomass variability along multiple cross-shore transects spanning marsh front edges, tidal creek networks, and interior zones.
Our results reveal that aboveground biomass consistently follows a parabolic spatial pattern along transects, with maximum biomass occurring at intermediate distances between the marsh front and interior. However, this general pattern is locally modified by tidal creeks, microtopography, and anthropogenic disturbances, leading to site-specific linear or segmented biomass–distance and biomass–elevation relationships. Transects intersecting tidal creek networks exhibit pronounced spatial heterogeneity, highlighting the organizing role of creek-induced elevation gradients and drainage conditions.
Temporal analysis further demonstrates that optimal biomass locations migrate synchronously with marsh front dynamics, indicating a strong coupling between vegetation growth and geomorphic evolution at decadal scales. These findings emphasize that spatial biomass patterns cannot be directly inferred from temporal biomass–elevation relationships alone.
Overall, this contribution highlights the importance of spatial heterogeneity and tidal creek systems in controlling salt marsh biomass distribution and provides empirical constraints for eco-geomorphic models that incorporate vegetation–topography feedbacks. The results are relevant for improving process-based simulations of salt marsh evolution under environmental change.
How to cite: Hang, J., Gong, Z., Jin, C., Huang, S., Xie, H., and Zhu, C.: Spatial patterns of salt marsh biomass and their geomorphic controls: evidence from central China’s tidal wetlands, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12932, https://doi.org/10.5194/egusphere-egu26-12932, 2026.
Tidal meanders are ubiquitous features of coastal ecosystems, controlling the exchange of water, sediment, and nutrient fluxes therein. The outer banks of tidal meanders typically undergo bank collapses, primarily triggered by the alternating actions of in-channel currents and seepage flow during periods of tidal exposure. As a result, tidal meanders frequently migrate across muddy flats, leaving substantial footprints of cutoff events. However, few studies have to date delved into this topic, primarily due to the challenge in obtaining high-resolution data to analyze their migration behavior. Here, we present field observations from the Jiangsu coast, China, to quantify tidal meander migration and its impact on planform geometry. During successive low tides, we apply UAV-based LiDAR to obtain centimeter-level DEMs of a main channel reach (~300 m wide) and its branching channels (~10 m wide). Unlike the relatively stable planform morphology commonly reported for salt marsh channels, we observed rapid lateral migration on silty flats (~10-3 m/s), leading to frequent cutoff formation. These observations highlight the highly dynamic nature of tidal meanders on muddy flats and underscore the role of bank collapse in shaping tidal-channel planforms. Our findings have important implications for understanding tidal-channel morphodynamics and associated eco-geomorphic feedbacks, including sediment redistribution and potential carbon release in coastal wetlands.
How to cite: Zhao, K., Lanzoni, S., Coco, G., and Finotello, A.: Field observation of rapid tidal meander migration on muddy flats, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13452, https://doi.org/10.5194/egusphere-egu26-13452, 2026.
Shoreline change in Ireland is frequently managed using suboptimal evidence: monitoring coverage is spatially and temporally limited, and decision support often relies on a small number of indicators used as proxies for complex coastal behaviour. This paper argues that shoreline vulnerability is not only a physical condition but is also partly produced through measurement methods. Choices about what is observed, and at what spatial and temporal scales, actively shape the narratives constructed about shoreline behaviour, whether coastlines are interpreted as persistently eroding, highly variable, or capable of recovery, with direct implications for prioritisation and adaptation. The study examines how the use of different proxies and observational scales generate divergent or complementary interpretations of shoreline change, and what these differences imply for translating evidence into management-relevant guidance. It is based on a three-year, multi-method monitoring programme across five contrasting beach systems along the County Cork coastline in Ireland (2023–2025), integrating long-term aerial imagery and vegetation-line change, Sustainable Coastal Vulnerability Index (SCVI) outputs, repeated seasonal cross-shore RTK-GNSS beach profiles, high-resolution UAV-derived orthophotos and digital surface models, and targeted post-storm assessments following major events.
A comparative narrative analysis is used to evaluate how each monitoring method characterises coastal change at each site. Results show that long-term shoreline proxies and derived change rates can mask more recent acceleration trends, regime shifts, or hotspots of erosion, particularly where accretionary and erosional phases offset each other over extended time periods or where anthropogenic modification constrains proxy behaviour. High-resolution field and UAV-based measurements reveal that many sites are dominated by cross-shore and alongshore sediment redistribution rather than uniform shoreline retreat, with erosion and accretion occurring simultaneously in different areas, and at recurring hotspots linked to access paths, structures, and channel dynamics.
Comparison with SCVI classifications demonstrates that index-based vulnerability assessments are effective for broad screening of exposure and receptors, but may overestimate or mischaracterise physical susceptibility where local sediment dynamics, management measures, or recovery processes are not represented. The research proposes a tiered, resource-aware monitoring framework. Repeated cross-shore profiles are shown to be sufficient for tracking seasonal dynamics and storm response in relatively uniform settings, while drone-derived surface models are most valuable where spatial complexity, structural controls, or management-relevant hotspots are present, provided that logistical and environmental conditions allow their deployment. By clarifying when proxy-based screening, profile surveys, or spatially continuous UAV products are most appropriate, the study provides guidance for designing efficient monitoring programmes that reduce interpretive bias and better support coastal adaptation decisions.
How to cite: Chalençon, E., Biausque, M., Cawkwell, F., O'Shea, M., and Murphy, J.: Through Proxy and Scale: How Measurement Choices Shape Narratives of Shoreline Change and Vulnerability along the southern Irish coast, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19080, https://doi.org/10.5194/egusphere-egu26-19080, 2026.
Coastal erosion poses a significant risk to India’s 11,098.81 km shoreline, particularly in regions where coastal economies rely heavily on fishing. Karaikal, Puducherry, has experienced erosion along 37% of its coastline (NCCR, 2018), underscoring the need for robust sediment volume and shoreline change assessments. This study quantifies sediment dynamics by integrating Unmanned Aerial Vehicle (UAV) photogrammetry with Real-Time Kinematic Global Navigation Satellite System (RTK GNSS) surveys across TR Pattinam and Vanjiur beaches. Shoreline positions were mapped using RTK GNSS by delineating the centre line between high-water (HWL) and low-water (LWL) marks, while UAV-derived edges were extracted via the Canny detection algorithm. UAV flights were conducted at 50 m altitude with 85% image overlap. The Canny method achieved an average SSIM of ~0.8 and positional accuracy within one pixel.
Sediment volumes were estimated by generating UAV-based digital elevation models (DEMs) using Structure from Motion and comparing them with centimetre-accurate GNSS transects spaced at 30 m intervals. Elevation differences were integrated alongshore to compute volumetric changes, with UAV elevations cross-checked against GNSS profiles for bias assessment. Results indicate strong agreement between UAV and GNSS datasets, demonstrating the reliability of this integrate.
Key words: Shoreline change, Erosion, GNSS, Edge detection ,Sediment volume
How to cite: Kalyana Kumar, P. P. and Ramalinga, S.: Precision Mapping of Coastal Erosion in Karaikal Using Combined UAV Photogrammetry and RTK GNSS Surveys, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1280, https://doi.org/10.5194/egusphere-egu26-1280, 2026.
Satellite derived shoreline position data from “CoastSat” has provided novel insights on the underlying climatic patterns driving cross-shore shoreline movement and shoreline rotation at many sites around the globe. Here we use CoastSat shoreline and wavelet coherence analysis to identify common scales between wave components and cross-shore shoreline change/alongshore shoreline rotation along the New Zealand coast. Wavelet-based decomposition was performed on two contrasting wave-climate regimes, comprising 250 km of west coast shoreline exposed to the Southern Ocean and 260 km of east coast shoreline influenced by the Southeast Pacific. A key challenge inherent to wavelet analysis of highly noisy satellite-derived data is determining statistical significance. Our approach estimates null hypothesis empirically using Monte Carlo red-noise simulations using the same effective number of degrees of freedom as presented in the real data. Thresholds change when scales or results from different sections (transects) of the coast are combined. Transect-averaged wavelet results indicate that, along the west coast, changes in wave height are consistently accompanied by changes in wave direction over the analysed period (1999-2024), implying that higher waves are associated with a single dominant direction. In contrast, the east coast exhibits multiple coherent signals, indicating that similar wave heights can occur under different directional regimes. Global coherence for the east coast (0.66 to 0.76) shows a high coherence in the seasonal band and the dominance of the alongshore component of the wave radiation stress in explaining beach rotation.
How to cite: Pullig, M., Bryan, K., and Coco, G.: Climate-Driven Cross-Shore Change and Shoreline Rotation Revealed by Satellite Observations , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4588, https://doi.org/10.5194/egusphere-egu26-4588, 2026.
Palaeotempestological studies provide a critical long-term context for understanding tropical cyclone variability beyond the short instrumental record, allowing past changes in typhoon frequency, magnitude, and coastal impact to be evaluated in relation to climate change. The exceptional sedimentary record produced by Typhoon Haiyan (locally Yolanda) in November 2013, offers a modern analogue that helps link projected intensification of tropical cyclones in warming tropical oceans to how extreme events may be preserved, and potentially misinterpreted, in the geological record. Haiyan, one of the strongest tropical cyclones on record, made landfall in the central Philippines and produced extreme storm surge and wave conditions that left sedimentary deposits closely resembling those of a tsunami. Post-storm field surveys documented extensive sand sheets extending onshore up to and exceeding 1km inland along parts of the Leyte and Samar coastlines that experienced severe inundation. These unusually far-reaching storm deposits occurred in coastal embayments and fringing reef settings where local hydrodynamic processes greatly amplified the surge and waves. In Leyte Gulf, funnel-shaped bathymetry and localised near shore dynamics from offshore winds caused the storm surge to steepen and reach ~5–6 m in height near Tacloban City, behaving much like a tsunami in its rapid flooding. Along exposed Pacific shorelines (e.g., Eastern Samar), incoming wave groups generated powerful infragravity-period oscillations (surf beat) that steepened into bore-like waves, overtopped a broad coral reef, and drove tsunami-like inland flooding. As a result of these processes, Haiyan’s overwash deposits exhibit a hybrid sedimentological signature with characteristics of both storm and tsunami deposits. For instance, boulders, multiple sand layers and coarse marine debris transported inland by successive wave bores were observed, which is atypical for ordinary storm deposits. Such infragravity wave influence and surge over-steepening make the Haiyan deposits a rare and anomalous case. Although they expand the known spectrum of cyclone-induced sedimentation, these deposits should probably considered outliers and should not be treated as representative “type” storm deposits. In fact, even under Haiyan’s extreme conditions, the sand sheets did not generally extend as far inland as those from large tsunami events, which remains a key distinguishing factor. Overall, the Haiyan example highlights how localised hydrodynamics and surf-beat processes can greatly exacerbate coastal flooding in embayments and reef-fringed coasts, and it underscores the need for caution when using Haiyan’s deposits as a model for storm-generated sedimentary records or sediment transport modelling.
How to cite: Switzer, A. and Soria, L.: Some lessons learned from the “tsunami-like” storm deposits from Typhoon Haiyan (2013) in the Philippines , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16852, https://doi.org/10.5194/egusphere-egu26-16852, 2026.
Due to climate change and global sea-level rise (GSLR), the Estonian coasts, like many other previously depositional coasts around the world, are becoming erosional. The objective of this study is to statistically analyse and model (both forecast and hindcast) changes in the coastal scarp at the Järve coast in southwestern Saaremaa, Estonia, taking into account recently documented and projected shifts in regional climatological forcing and sedimentological background. Due to postglacial rebound with a local uplift of 2.2 mm/a over the Middle and Late Holocene, the area emerged from the sea about 4000 years ago. However, the growth of the uplifted coastal barrier, which has fully merged with the Saaremaa mainland, has essentially ceased, and the coast has largely become erosional. GSLR has recently outweighed the local postglacial sea-level lowering; storminess patterns have changed; the number of ice days has nearly halved in Estonia over the past ~100 years, and these tendencies are expected to continue.
To statistically analyse past changes and project future coastal developments, matrices of annual forcing data, including 13 selected and presumably most influential parameters (such as wind speed components, storminess indicators, average and maximum sea levels, air temperatures, and sea-ice statistics from neighbouring meteorological-hydrological stations), are juxtaposed with parameters describing the geomorphic outcomes observed at five selected cross-shore profiles on the currently erosional Järve coast, as well as at the downdrift, accretional Mändjala site. Variations in volumetric (erosion-accretion) changes in the scarp above the mean sea-level elevation and changes in scarp position are examined for the period 1990-2025.
Although the forcing parameters were chosen to minimize mutual duplication, the multivariate statistical analysis (correlation matrices and principal component analysis) yielded three major forcing composites. These were related, first, to gently varying, mainly NAO-related fluctuations in winds, storms and relative sea level; second, to the continuous warming trend, characterized by increasing air temperature and decreasing numbers of ice days; and third, to occasional (catastrophic and NAO-independent) storm-surge events. It was found that extreme storms can cause significant geomorphic changes not only during the event but also over longer periods. Such events produce immediate scarp erosion of several meters and deliver large volumes of fine-grained sediment to the nearshore zone, where it can be readily redistributed along the coast in subsequent years, leading to enhanced accretion in depositional areas even under relatively low forcing conditions. Furthermore, multivariate statistical models (including Principal Component Regression and forecasting), as well as machine-learning techniques (e.g., Random Forest, Boosted Trees, Support Vector Machines), relating the suite of forcing conditions to geomorphic outcomes for each profile, were tested. The forcing sets were manipulated to predict future developments along the Järve-Mändjala erosional-accretional coast. In addition, using older (observed and partly reconstructed) meteorological-oceanographic data on relative sea level, air temperature, ice conditions, and storm surges, the coastal changes were back-traced to pinpoint the mode change from areal increase and barrier growth to coastal erosion, which is hypothesized to have occurred approximately 50–100 years ago.
How to cite: Tõnisson, H., Luik, K., Mäll, M., Koit, O., Suuroja, S., Jaagus, J., and Suursaar, Ü.: Forecasting and Hindcasting Coastal Scarp Dynamics Using Forcing Composites and Machine-Learning Models in Saaremaa, Estonia, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2558, https://doi.org/10.5194/egusphere-egu26-2558, 2026.
Posters on site: Wed, 6 May, 16:15–18:00 | Hall X3
The shore platforms around Kaikōura Peninsula, located on the tectonically active east coast of South Island, Aotearoa New Zealand, host the world’s longest-running erosion monitoring record. Since 1973, a network of micro-erosion meter (MEM) stations has been used to measure downwearing across mudstone and limestone platforms to explore processes responsible for and the rate of development of the shore platforms. Here, we review and report on five decades of observations, assess spatial and temporal patterns of erosion and evaluate the consistency of downwearing rates. Although never originally intended as part of the programme, we can now quantify the geomorphic response to one metre of coseismic uplift associated with the 2016 Mw 7.8 Kaikōura earthquake. Pre-earthquake erosion rates averaged 1.00 mm/yr (STDV = 0.73) across 9 measurement epochs. Post-earthquake rates more than doubled to 2.54 mm yr-1 reflecting enhanced subaerial weathering on the uplifted surfaces. Limestone platforms tended to erode more slowly (1.30 mm/yr) than mudstone (3.27 mm/yr), a significant difference between the two rock types that had not been evident before the 2016 uplift. Seasonal differences in erosion with higher rates in summer than winter observed prior to the earthquake remained pronounced after 2016 but the subaerial processes responsible have likely changed. These findings highlight the critical role of changing processes, the geomorphic significance of tectonic events on rock coasts, and the pathway from shore platform to marine terrace generation. The Kaikōura dataset provides a reference for interpreting short- and long-term erosion dynamics and highlights the scientific legacy of the late Emeritus Professor R.M. (Bob) Kirk.
How to cite: Stephenson, W.: Fifty Years of Shore Platform Erosion Monitoring at Kaikōura Peninsula, South Island, Aotearoa-New Zealand, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2123, https://doi.org/10.5194/egusphere-egu26-2123, 2026.
Quantifying shore platform evolution at appropriate spatial and temporal scales remains challenging due to the complex scaling between erosion at the instantaneous scale from waves and granular decay and the centennial to millennial age of platform systems. Unique multi-decadal records of in situ Micro-Erosion Meter (MEM) measurements, spanning more than 40 years, are available from shore platforms on the Kaikōura Peninsula, South Island, New Zealand, and the Otway Coast, southeastern Australia. MEM observations from Kaikōura indicate that, following 1 m of coseismic uplift during a Mw 7.8 earthquake in 2016, mean platform lowering rates have averaged ~2.30 mm/yr. In contrast, MEM measurements from the tectonically stable Otway shore platform between 2015 and 2024 indicate lower erosion rates of 0.264 mm/yr. While the MEM provides high-precision point-scale erosion rates, its spatial and temporal coverage is limited relative to the full extent and evolutionary timescales of shore platforms. To overcome these limitations, this study integrates Interferometric Synthetic Aperture Radar (InSAR) with GNSS observations to extend erosion and deformation assessments across entire shore-platform surfaces. Persistent Scatterer Interferometry (PSI) was applied using the Surface motioN mAPPING (SNAPPING) PSI Med and PSI Full services on Sentinel-1 imagery acquired between 2017 and 2024 and processed via the Geohazards Exploitation Platform. At Kaikōura, PSI Full analysis indicates an average uplift rate of 4.28 mm/yr, whereas PSI Med analysis yields an apparent subsidence rate of 1.76 mm/yr, highlighting scale- and processing-dependent variability in deformation estimates. Initial InSAR results from the Otway Coast reveal low-magnitude deformation, with velocities generally ranging between −2.0 and +2.0 mm/yr. GNSS observations located at the Kaikōura Peninsula provide an independent constraint on vertical motion, indicating net subsidence at Kaikōura of approximately 3.0 mm/yr between 2017 and 2024. GNSS stations near the Otway shore platforms record subsidence rates of ~3.75 mm/yr at Lorne (2022–2024) and ~1.54 mm/yr at Marengo (2017–2024). Further analysis is required to reconcile GNSS-derived vertical motion rates with MEM observations; however, initial results highlight the value of integrating MEM, InSAR, and GNSS to resolve shore-platform downwearing across multiple spatial scales.
How to cite: Hossain, M. S., Stephenson, W., Denys, P., Dickson, M., Kennedy, D. M., and Yuan, R.: Using InSAR and GNSS to estimate shore platform erosion of Kaikōura Peninsula, New Zealand, and Otway Coast, Australia, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6348, https://doi.org/10.5194/egusphere-egu26-6348, 2026.
The dislodgement and transportation of boulders on rocky coasts by storm waves has been the subject of an increasing number of studies in the last decade. Research has been approached from different perspectives, such as numerical models that hindcast wave heights that produce movement, structural control on boulder production, and innovative monitoring and change detection techniques. However, the complex dynamics between boulders and wave forces that determine boulder mobility remain insufficiently understood.
This ongoing study aims to document instances of boulder displacement and quantify their frequency over a two-year observation period. Monitoring is being conducted at three coastal sites across the Maltese Islands (Central Mediterranean): one in Qawra (northern coast) and two in Marsascala (southern coast). Data acquisition is conducted periodically using unmanned aerial vehicles (UAVs), with subsequent 3D model reconstruction performed using Agisoft Metashape. Each newly generated model is compared to its predecessor to detect changes in boulder positions.
Observed boulder movement is evaluated based on key parameters including size, morphology, initial location, displacement distance, and direction of transport. These transport events are then correlated with wave conditions recorded during the interval between successive UAV surveys.
Preliminary findings from the first six-month monitoring phase at Qawra are being presented here. These results suggest that boulder mobility is influenced by a combination of factors, including boulder morphometry and location, coastal topography, wave energy, and wave direction relative to shoreline orientation.
How to cite: Gauci, R., Causon Deguara, J., and Inkpen, R.: A temporal assessment of boulder mobility on a limestone rocky coast in Qawra, Malta (Central Mediterranean), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11761, https://doi.org/10.5194/egusphere-egu26-11761, 2026.
Aeolian sand-trap design plays a critical role in quantifying and interpreting wind-driven sediment transport in coastal and other exposed environments. Traditionally, sand traps have been developed primarily to measure mineral sand fluxes and to mitigate the adverse effects of aeolian transport on infrastructure and landscapes. Aeolian processes also act as an important vector for redistributing organic material, including seeds and other biologically relevant components embedded within the sand environment, which are essential for dune development, vegetation dynamics, and ecosystem resilience. Optimising sand-trap design is therefore necessary not only to accurately capture sand transport rates and directions but also to enable a more representative assessment of the coupled transport of mineral and organic material.
In this study, we assess and optimise aeolian sand trap designs for application along the Lithuanian Baltic Sea coast, with particular focus on the highly dynamic dune systems of the Curonian Spit. Two commonly used designs are evaluated: the Big Spring Number Eight (Fryrear) trap and an omnidirectional cylindrical trap. Their performance is examined under local aeolian conditions using numerical simulations that capture characteristic wind regimes, seasonal variability, and typical sand-grain-size distributions. Airflow modelling and particle trajectory analyses are applied to investigate how trap geometry, inlet configuration, and installation height influence capture efficiency and directional sensitivity.
The sand trap designs are analysed within a computational fluid dynamics (CFD) framework using a finite-volume method (FVM) solver, enabling a detailed assessment of aerodynamic behaviour and sand interception processes. The optimal trap design for long-term monitoring in Lithuanian coastal areas will be chosen and optimised based on the modelling results. These findings will support the development of a field-ready prototype to be deployed as part of an ongoing monitoring programme on the Curonian Spit to detect changes in aeolian transport related to recent shifts in dune vegetation cover. This will also support better coastal management and dune restoration efforts.
How to cite: Kelpsaite-Rimkiene, L., Tadžijevas, A., Šapalas, D., Dumbrauskas, B., Žalys, M., and Kondrat, V.: Evaluation and Optimisation of Aeolian Sand Trap Designs, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16397, https://doi.org/10.5194/egusphere-egu26-16397, 2026.
Gravel barriers are efficient absorbers of wave energy due to the high permeability of gravel sediments. They are thus highly valued as a coastal defence and have numerous other benefits including biodiversity and recreation. Given the probable increase in storm intensity under climate change, this importance will only increase in the future. However, these systems can themselves be damaged during storm events. To effectively manage and monitor them, it is necessary to understand how they respond to energetic forcing. Thus far, morphological and hydrological measurements of sufficient resolution to resolve individual swashes are rare on gravel environments, especially over a protracted period time. Hence, our current knowledge is lacking.
As part of the #gravelbeach project, this study addresses this knowledge gap by investigating swash-level change at different gravel barrier typologies. Here, we focus on Borth, a drift-aligned macrotidal composite barrier in West Wales. A 6 m LiDAR tower was deployed between 28 November 2024 – 25 March 2025. Three-second scans were taken every low tide, while one-to-two hour scans were taken every high tide. The shoreline is extracted every 1 s, from which the total water level and bed profile are calculated. To extract berm location and characteristics, a novel semi-automated approach is developed.
During the transition from neap to spring tide, a series of berm construction and destruction events is observed, which is in contrast to prior observations of a gradual translation. At the swash level, four different types of berm response to energetic events were identified. They could flatten, overtop, aggradate vertically, or possess an upper zone of accretion (making the local profile gentler) and a lower zone of erosion (making the local profile steeper). It is also demonstrated that a gravel barrier can change between these types rapidly; in one example, three types are displayed in a single two-hour period. This diversity in barrier slope, both temporally and spatially, is often not taken into account by modelling approaches and highlights the need for continued research into swash-level dynamics at gravel barriers.
How to cite: Jones, R., Valiente, N., Blenkinsopp, C., and Davidson, M.: Using 2D LiDAR to Investigate Swash-Level Gravel Barrier Dynamics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2018, https://doi.org/10.5194/egusphere-egu26-2018, 2026.
This study examines Holocene sea-level rise and associated coastal and estuarine geomorphic evolution of the Nakdong River delta, South Korea, with a particular focus on east–west variations in depositional environments. Previous studies have largely reconstructed delta development based on north–south-oriented sediment cores, implicitly assuming along-axis uniformity. However, the Nakdong River estuary is characterized by an asymmetrical incised-valley morphology that extends farther eastward, suggesting spatially heterogeneous geomorphic responses to Holocene transgression and delta progradation. To address this gap, we analyzed sediment cores collected along an east–west transect across the estuarine valley, integrating chronological constraints and detailed sedimentary facies analysis. Preliminary results reveal a marked contrast in Holocene geomorphic evolution between the two sides of the valley. Thick Pleistocene deposits persist in the western valley, indicating limited accommodation creation, whereas early Holocene inundation and sediment accumulation commenced earlier in the eastern valley. By ~7 ka, marine influence had expanded across the entire valley, reflecting regional sea-level rise. Notably, prodelta and delta-front facies indicative of active delta progradation and shoreline advance are restricted to the eastern valley, suggesting preferential delta growth controlled by inherited valley morphology. In contrast, the western valley is dominated by tidal-flat and salt-marsh facies, implying a geomorphic setting characterized by lateral sediment trapping and restricted shoreline progradation. These east–west contrasts highlight the importance of valley-scale geomorphology in modulating coastal response to Holocene sea-level rise. This study provides new insights into the spatial variability of deltaic geomorphic evolution in a tide-influenced estuary and contributes to a broader understanding of Holocene coastal landscape development in East Asian river deltas.
How to cite: Han, M. and Yoon, H. H.: East–west contrasts in Holocene coastal geomorphic evolution of the Nakdong River delta, South Korea, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6385, https://doi.org/10.5194/egusphere-egu26-6385, 2026.
Coastal boulder deposits are found worldwide on rock coasts and can serve as a record of extreme wave events. Boulder dimensions are key parameters in commonly used hydrodynamic equations for reconstructing the extreme wave events which likely emplaced them, providing data that can inform coastal hazard assessments. Traditionally, boulder dimensions are measured in the field using a tape measure, a process that can be time-consuming when collecting large datasets. Remote sensing approaches are increasingly being used in the measurement of coastal boulder deposits to extract boulder parameters. Orthomosaics generated from unmanned aerial vehicles (UAVs) allow for individual boulders to be measured using either manual or automated digitisation techniques. By digitising the outlines of boulders, a minimum bounding box can be fitted, and parameters such as orientation and axis lengths extracted. Large, site-wide datasets of these values can be rapidly generated, enabling whole site characterisation. However, this technique has only seen limited validation, particularly at sites with clustered boulders and an uneven basement surface. This study compares UAV-derived measurements of boulder dimensions with traditional field measurements, to test the statistical similarity.
The Grind o’ da Navir, Shetland, has an abundance of demonstrably storm wave emplaced boulders, which form ridges across the 15 – 20 m high cliff top. The site was selected due to its uneven bedrock and complex boulder ridge morphology, providing a boulder-abundant but methodologically-challenging environment. From 7950 digitised boulders, the mean long (A) axis was 0.66 m and the intermediate (B) axis was 0.40 m, with maximum axis lengths of 3.37 m and 1.73 m respectively. When compared using a paired subset of the data, the digitisation and traditional methods have a mean difference in A-axis of 0.05 m, and of 0.02 m for the B-axis, with a standard deviation of 0.14 m and 0.12 m for the two axes, respectively. This shows that the two methods are broadly interchangeable for average statistics with only minor bias, but individual measurements may have a larger error. The dip angle of boulders within the ridges at the Grind likely contributes to these individual measurement errors. At sites with isolated boulders on flat platforms, such discrepancies would be expected to be considerably smaller. Thus, UAV-derived boulder outlines can generate site-wide boulder statistics more rapidly than traditional field methods, with reasonable accuracy. The digitisation method can complement traditional field techniques, enabling larger, spatially extensive datasets while reducing the likelihood that spatial variability in boulder characteristics is overlooked.
How to cite: Roberts, S., Raby, A., Manzella, I., and Boulton, S.: Do UAV-Derived Boulder Dimensions Match Traditional Field Measurements at the Grind o’ da Navir, Shetland?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6723, https://doi.org/10.5194/egusphere-egu26-6723, 2026.
Coasts are land–ocean interfaces of high environmental and economic value. They are among the areas most affected by urbanisation and economic activities. Increasing anthropogenic pressure has significantly altered ecosystem structure and services, reducing the quality and quantity of natural resources, causing habitat and biodiversity loss, and transforming coastal landscapes from natural to anthropogenic.
The Italian coastal area is highly anthropised, with 34% of the population permanently residing in coastal cities. The Italian coastline is approximately 8,300 km long, 13% of which is occupied by artificial structures, with an increase in coastal artificialisation of over 100 km in the last 20 years.
The study area is in the Gulf of Trieste, a shallow semi-enclosed sea of about 500 km² in the north-eastern Adriatic Sea, in the Italian region of Friuli Venezia Giulia (FVG). The FVG coastline extends for 111 km, of which 55.4% is highly anthropised.
The south-eastern coasts of the gulf, from Grignano to Muggia, have been extensively built up and modified by human activities, particularly near Trieste, where both the natural coastline and the seabed have been heavily altered.
The aim of the study is to evaluate and quantify the evolution and changes (advances and retreats) of the predominantly rocky coastline of the eastern Gulf of Trieste, caused by anthropogenic activities over the last 200 years.
To conduct the analysis, a series of historical and modern charts of the study area from the last 200 years were collected. After georeferencing the charts, past coastlines were digitised and compared with each other and with the current one using a Geographic Information System (GIS).
Polygons were generated to represent coastline advances and retreats, and the respective areas were calculated. Histograms were produced to illustrate the temporal distribution and extent of coastal changes over the study period. To assess the type of human pressure, each coastline change was analysed in relation to its cause and the intended land and sea use at the time it occurred.
The analysis showed that in some areas, advances caused by human activity reached several hundred metres, mainly due to the construction of infrastructure, ports, and industrial settlements.
How to cite: Pagano, M. and Busetti, M.: Analysis of anthropogenic coastline changes in the Gulf of Trieste (NE Adriatic Sea) over the last 200 years in GIS environment, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10576, https://doi.org/10.5194/egusphere-egu26-10576, 2026.
Rocky coasts evolve under the combined actions of rock uplift and erosive processes. These processes are mostly related to the sea-land interface but have varied mechanisms, ranging from wave-driven rock fatigue and cliff collapse to efficient salt weathering in the intertidal zone. The relative importance of these processes remains poorly quantified and is rarely addressed directly in modeling efforts. In particular, widely used coastal-erosion models are rarely subjected to systematic, field-informed testing that explicitly separates the contributing processes, limiting confidence in their transferability across sites.
Here we present a modelling framework that evaluates and extends wave-driven cliff–platform models by separating process regimes and representing coastal erosion as a modular combination of mechanisms. We implement the framework in xarray-simlab (Xsimlab) which facilitates modular model construction and systematic comparison of process combinations. We implement and compare formulations for (i) talus production and removal at cliffs, (ii) intertidal weathering that drives vertical downwearing of the intertidal platform, and (iii) subaqueous wave-driven horizontal backwearing with nearshore energy dissipation.
Our results show that different combinations of these processes—and their relative contributions—produce markedly different styles of erosional topographic evolution, leading to divergent long-term trajectories and contrasting marine-terrace preservation. This highlights the need to reconsider which model components are appropriate for different geomorphic settings. By exploring combinations of these modules across representative wave and tectonic, and lithological scenarios on the Noto Peninsula and Sado Island (Japan), we assess how shifts in process dominance generate distinct modern shoreline configurations and, ultimately, different coastal morphologies.
How to cite: Keum, D., Malatesta, L., Tsukamoto, S., Norton, K., Braun, J., Bovy, B., and Kim, Y.: Developing a modular and multi-process modeling framework for rocky-coast evolution, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12885, https://doi.org/10.5194/egusphere-egu26-12885, 2026.
Coastal dune systems in (hyper)arid environments provide exceptional natural laboratories for studying aeolian morphodynamics and sediment routing. In the southern Atacama Desert (Chile), a barjanoid dune field and two longitudinal dunes located in close proximity form a highly dynamic inland‑migrating system sourced from coastal sands redistributed by persistent SW winds. In this study, we digitized these dune types from multitemporal satellite imagery from 2005 to 2023 and analysed their 18-year spatio-temporal evolution, focusing on migration rates, morphometric characteristics and the geomorphic controls that govern their trajectories. The barjanoid dune field consists of 4–5 sinuous crests perpendicular to the prevailing winds whose migration rates vary significantly according to their position relative to a Late Pleistocene marine terrace. Crests located on the terrace slope exhibit low net migration (Net Shoreline Movement [NSM]: 3–36 m; Linear Regression Rate [LRR]: 1.14–2.35 m/yr), whereas those that have surpassed the topographic break show markedly higher displacement (NSM: 49–59 m; LRR: 3.80–4.21 m/yr). This sharp contrast demonstrates that terrace gradients act as temporary sediment traps, delaying crest propagation until the accumulation threshold is overcome. To the east of the barjanoid dune field, both longitudinal dunes, parallel and approximately 75 m apart, emanate from a sediment source just landward of the marine terrace, and show sinuous crests that reflect a slightly bi-directional wind regime. However, the first one displays significantly shorter length and faster migration rates than its counterpart to the east (630 and 1275 m and 6.75 and 4.7 m/yr, respectively). These differences, which need further investigation, may reflect variations in proximity to the barjanoid dune field acting as a dynamic sediment supplier, as well as pronounced disparities in dune dimensions, likely reflecting distinct formation times. Additionally, it was observed that both longitudinal dunes could originate from the barjanoid dune crests surpassing the marine terrace and rotating to be aligned with the prevailing wind direction. Together, these results reveal a morphodynamic system strongly conditioned by sediment supply pathways, topographic barriers and inherited deposits. The contrasting behaviours observed suggest sequential formation phases and spatial reorganization of the aeolian system. Integrating migration rates, sediment pathways and terrace-controlled dynamics offers new insights. These findings improve our understanding of coastal dune evolution in tectonically active, sediment-limited arid coasts. The authors thank project PID2021-127268NB-I00 funded by MCIN/AEI /10.13039/501100011033 and by FEDER/UE.
How to cite: Abad de los Santos, M., Veintimilla García, R. I., Talavera, L., and Izquierdo, T.: Morphodynamics of barjanoid and longitudinal dune systems in an arid coastal desert (Atacama, Chile), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13987, https://doi.org/10.5194/egusphere-egu26-13987, 2026.
Accurate shoreline monitoring is critical for coastal zone management in tectonically active regions. However, in micro-tidal environments like the coast of NW Türkiye, the positional accuracy of freely available satellite data remains poorly quantified. The key uncertainty is whether observed errors stem from sensor limitations or short-term environmental noise, hindering reliable sensor selection for operational use.
We conducted a rigorous benchmark analysis using centimeter-precision Unmanned Aerial Vehicle (UAV) Structure-from-Motion (SfM) data as the definitive reference. Shorelines were extracted from Sentinel-2 MSI, Landsat 8 OLI, Sentinel-1 SAR, and Copernicus DEM GLO-30 using Google Earth Engine (GEE) and compared using transect-based metrics (RMSE, MAE) at two contrasting sites: the complex rocky coast of Güneyli (Gulf of Saros) and the urbanized sandy coast of Altınova (Sea of Marmara).
Our analysis reveals a critical finding: all satellite sensors exhibited RMSE values clustered between 8–15 m. This range aligns with the magnitude of expected hydrodynamic noise (e.g., wave run-up) in such micro-tidal settings, suggesting an environmental constraint on practical accuracy. Site-specific patterns emerged: In urbanized Altınova, Sentinel-1 SAR achieved the lowest RMSE (8.79 m), proving robust against spectral confusion from anthropogenic structures. In natural Güneyli, Sentinel-2 demonstrated superior geometric fidelity with the lowest MAE (7.45 m), effectively capturing complex morphology obscured by radar speckle. The Copernicus DEM was consistently unsuitable for precise delineation, with errors exceeding 15 m due to vertical uncertainties amplified by coastal topography.
This study establishes that in micro-tidal, active margins, environmental variability sets a practical accuracy floor (~10 m) for operational satellite monitoring. Therefore, we propose a tiered framework: (1) Sensor choice must be context-driven (SAR for modified coasts, optical for natural settings), (2) Detected changes near this threshold require caution, and (3) High-resolution UAV data is indispensable for validation and for resolving sub-satellite-scale geomorphic features (e.g., submerged beachrock geometry) critical for hazard assessment. Our work thereby provides a calibrated benchmark for coastal scientists and managers.
This work was supported by the Scientific and Technological Research Council of Türkiye (TÜBİTAK) under the Grant Number 119Y567.
How to cite: Geyik, M. and Tarı, U.: Validating Satellite-Derived Shorelines with UAV-SfM: A Multi-Sensor Accuracy Study in NW Türkiye , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16698, https://doi.org/10.5194/egusphere-egu26-16698, 2026.
Sea level rise is a key effect of modern climate change. The ~500 km-long Scania coastline is uniquely sensitive within Sweden to sea level rise (SLR) because it is mostly formed of sediments and its low-lying topography hosts extensive built environments. Swedish municipalities are legally obliged to include climate- and erosion-related risks in their spatial planning. However, it is a challenge for coastal municipalities to fully comply with the legal requirements because the scientific basis is currently difficult to interpret for coastal adaptation to sea level rise and there is still limited research describing the effects of sea-level rise on erosion along Swedish coasts. Our research is addressing these shortcomings through: (i) developing physical process-based predictions of erosion driven by sea level rise for the Scania coastline; and (ii) alongside end-users, co-creating an understanding of how erosion predictions are best communicated to make them accessible, actionable and relevant from the end-user’s perspective. Key challenges to predicting coastal response to sea level rise in southern Sweden include complex topography, varying wave and sediment conditions, and limited material supply. Because of shortcomings in the scientific understanding of SLR-driven coastal erosion, we take an ensemble approach that combines deterministic and probabilistic methods. Our preliminary modelling has focused on translation of equilibrium profiles of different shapes to estimate erosion. We find that a gradual increase in sea level, where the translated profile at the previous time step is used as input to the next step, induces more erosion than an instantaneous shift over the total sea level rise, because more material is deposited in the offshore during this iterative procedure. Our modelling of shoreline responses is being further developed and predictions of coastal response to sea level rise, including analyses of probabilities, will be communicated to our end-users using a GIS platform.
How to cite: Goodfellow, B. W., Almström, B., Bokhari Irminger, S., Ising, J., Karlsson, M., Larson, M., Lundgren Sassner, L., and van Well, L.: Predicting shoreline response to sea level rise along the varying coastline of Scania, southern Sweden, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16839, https://doi.org/10.5194/egusphere-egu26-16839, 2026.
The pace of erosion processes leading to the landward retreat of rocky cliffs could possibly be enhanced by climate change and rising sea level conditions. Satellite and aerial imagery provide a means for quantifying rocky cliff retreat at decadal scale, while retreat rates over several millennia can be estimated by measuring the concentration of cosmogenic nuclides of samples taken from abrasion platforms. In this contribution we analyze the evolution of rocky cliffs at two locations of the Cantabrian coast in northern Spain, both located in the Asturias region, by combining these techniques. The analysis of aerial images shows that one of the sites has remained quite stable over the last decades, while the other stands evidence of active slope instabilities over, at least, the last two decades. The cliff retreat rates estimated based on 10Be concentration measurements from abrasion platforms preserved at the cliff base at both study sites are compatible with slow rates of retreat, of the order of a few centimeters per year.
Research funding: RETROCLIFF (PID2021-122472NB-100, MCIN/AEI/FEDER, UE) and GEOCANTABRICA (IDE/2024/000753, SEK-25-GRU-GIC-24-072, SEKUENS, Principado de Asturias).
How to cite: Rodríguez-Rodríguez, L., Domínguez-Cuesta, M. J., Braucher, R., Cuervas-Mons, J., Aumaître, G., Keddadouche, K., Zaidi, F., and Jiménez-Sánchez, M.: Rocky cliff evolution in the Cantabrian coast (N Spain), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18288, https://doi.org/10.5194/egusphere-egu26-18288, 2026.
Coastal dune systems play a key role in coastal environments, acting both as natural barriers against marine processes and as freshwater storage reservoirs. These systems are dynamic, making assessment and long-term monitoring of geomorphological changes essential for coastal management. The study investigates the evolution of a coastal dune system from the 1970s to the present day through a multi-temporal and multi-source analysis. The study performed a comparative analysis by extracting key coastal geomorphological features (e.g., dune crest lines, dune foot boundaries, shoreline, and lateral dune extension) from historical cartographic data, orthophotographs, and digital terrain models (DEMs). The methodology integrates photogrammetry, digital elevation modeling, and GIS-based techniques to quantify spatiotemporal changes in dune geometry. Results show progressive dune retrogradation, accompanied by a significant decrease in dune extent and elevation, indicating a condition of coastal erosion. These changes are consistent with a decrease in the potential freshwater storage capacity of the coastal aquifer and an increased vulnerability to saltwater intrusion. The study area is located along the southern coast of Ravenna (Italy) and is conducted within the framework of the LIFE NatuReef project. The analyzed dune system represents a unique protected remains within a highly urbanized and tourist coastal context, highlighting its ecological relevance and vulnerability.
How to cite: Faelga, R. A., Carlini, C., Silvestri, S., Ponti, M., and Giambastiani, B. M. S. and the LIFE NatuReef Project: Spatiotemporal analysis of coastal dune features and implications for groundwater resource using an orthophoto-based approach, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18634, https://doi.org/10.5194/egusphere-egu26-18634, 2026.
