ABSTRACT: The Mediterranean basin is a climatically sensitive transition zone between mid-latitude and subtropical circulation regimes, where modest forcing can produce pronounced hydroclimatic and coastal impacts (Ben Ameur et al., 2019 and 2022 and 2024). Here we investigate Late Holocene marine and hydrological variability along the arid Tunisian margin using a sediment archive from the Oued El Fedj delta (western shore of the semi-enclosed Boughrara Lagoon, Gulf of Gabès). A 268 cm long sediment core was retrieved from the downstream deltaic plain and analysed using magnetic susceptibility, grain-size distribution (modal grain size, sorting and frequency-curve partitioning), and carbonate content, all measured at 1 cm sampling intervals, together with XRF geochemical scanning of major and trace elements on 16 representative samples.

Two intervals show a clear increase in carbonate and marine influence, expressed by upward shifts in CaCO₃ and elevated Ca/Ti, Ca/Si, Ca/Al, and Ca/Fe ratios: (i) a carbonate-rich unit at 173–200 cm, tentatively correlated with the Late Holocene highstand/transgressive phase reported for southern Tunisia (~2.5–2.0 ka BP; Paskoff and Sanlaville (1983)), and (ii) an upper unit at 30–57 cm reflecting the ongoing historical-to-modern marine ingression. Both intervals are characterized by poor sorting and polymodal grain-size distributions spanning namely silt (4- 63 µm), very fine (63-125 µm), fine (125- 250 µm), medium (250- 500 µm), and coarse sands (500 µm- 1 mm), consistent with mixed depositional processes in a lagoon–delta setting.

Episodes of intensified fluvial activity are identified by prominent magnetic-susceptibility peaks at 95–140 cm and 20–35 cm, interpreted as enhanced detrital input during high-discharge/flood phases. The older pulse postdates the ~2.5–2.0 ka marine interval and may align with increased hydrological variability during the Dark Ages Cold Period (~1.4–1.0 ka BP) documented in Tunisian sebkha archives, whereas the younger pulse occurs during the recent marine ingression, suggesting coupled relative sea-level rise and flood-driven sediment delivery.

Keywords: Southern Mediterranean; Southeastern Tunisia; Boughrara Lagoon; Late Holocene; relative sea level; flooding event; magnetic susceptibility.

References:

Ameur, M. B., Masmoudi, S., Abichou, A., Medhioub, M., & Yaich, C. (2019). Use of the magnetic, geochemical, and sedimentary records in establishing paleoclimate change in the environment of Sebkha: Case of the SebkhaMhabeul in southeastern Tunisia. Comptes Rendus Geoscience, 351(7), 487-497.

Ben Ameur, M., Masmoudi, S., Omar, H., Ouameni, I., Medhioub, M., & Yaich, C. (2022). Middle to late Holocene sedimentary filling history of the Sebkha el Melah in south-eastern Tunisia. Sedimentology, 69(5), 2348–2366. https:// doi. org/ 10. 1111/ sed.

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Ben Ameur, M., Masmoudi, S., Omar, H., & Yaich, C. (2024). Centennial‑scale flood cyclicity in the second half of Holocene in the southeast Tunisian sediments: paleoenvironmental region gauge between the western and eastern Mediterranean. Journal of Sedimentary Environments, 9, 625–644. https://doi.org/10.1007/s43217-024-00185-7.

Paskoff, R., &Sanlaville, P. (1983). Les côtes de la Tunisie. Variations du niveau marin depuis le Tyrrhénien (Vol. 14, No. 1, pp. 0-0). Maison de l'Orient et de la Méditerranée Jean Pouilloux.

How to cite: Ben Ameur, M., Omar, H., Masmoudi, S., and Yaich, C.: Late Holocene marine incursions and hydrological extremes recorded in the Oued El Fedj delta (Boughrara Lagoon, SE Tunisia), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2381, https://doi.org/10.5194/egusphere-egu26-2381, 2026.

Understanding coastal processes at work under past climates remains key to anticipating future scenarios. The Atlantic Coast of South America preserves records of Plio-Pleistocene and Holocene sea level in elevated marine deposits–especially along the coast of Patagonia in Argentina, where recent efforts have focused on compiling and refining Holocene sea level estimates. Here, we examine the internal structure of Holocene gravel beach deposits within an embayment at Bahía Laura, Argentina, to explore the dynamics at play over the past ~6 ka. Interpretation of over two kilometers of topographically-corrected Ground Penetrating Radar (GPR) profiles tells the story of generally consistent regression and progradation associated with falling or stable relative sea level (RSL) since a mid-Holocene highstand. Further, consistent supply of gravelly sediments likely stems from a combination of an eroded Pleistocene terrace perched immediately above the Holocene sequence, reworked near shelf sediments, and fluvial contribution from the south. Erosional surfaces and berm ridges visible within the profiles document high energy storm events and a shift in slope and spacing between radar reflectors along profiles may chronicle changing wave direction, accommodation space, sediment supply, and/or rate of sea level change.

How to cite: Melly, J., Montes, A., Ruiz, P., Gowan, E., Ryan, D. D., Kumar, R., Huang, W., Switzer, A., Goodwin, I., and Rovere, A.: Near subsurface investigations of South Atlantic paleo beach processes at Bahía Laura, Patagonia, Argentina, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3159, https://doi.org/10.5194/egusphere-egu26-3159, 2026.

Coastal dune systems are fundamental transitional geomorphological features that function not only as natural barriers for coastal protection but also as valuable geo-archives capable of recording the evolutionary dynamics of coastal landscapes. Along the Italian coasts, the formation and stabilization of these systems during the Holocene and historical periods have been shaped by a complex interplay between post-glacial sea-level rise, variability in fluvial sediment supply, and increasingly significant anthropogenic impacts. This contribution provides a systematic review of dated coastal dune systems across the Italian peninsula and its major islands. The primary objective is to synthesize current knowledge and establish a consistent chrono-stratigraphic framework. By integrating geomorphological data, radiometric dating (OSL and ¹⁴C), geoarchaeological evidence, and historical cartography, this study analyzes the spatial and temporal distribution of dune ridges. This integrated approach allows for the identification of synchronous phases of stabilization and progradation at a regional scale, offering a comprehensive perspective on how Mediterranean shorelines have responded to Late Quaternary forcing factors. A key focus of this ongoing research involves utilizing these dated dune sequences as high-resolution proxies for quantifying coastal progradation rates. By correlating the spatial position of dune bodies with their absolute ages, it is possible to derive estimates of shoreline advancement rates across diverse physiographic settings, such as deltaic lobes, open coastal plains, and embayed sectors. This methodology enables a distinction between periods of rapid progradation often linked to high sediment supply or sea-level stabilization—and phases of coastal stability or erosion. In conclusion, this review demonstrates that the integrated study of Italian coastal dunes is not only essential for paleogeographic reconstruction but also provides vital quantitative parameters (progradation rates) for understanding coastal resilience. Such data are crucial for calibrating evolutionary models in response to contemporary sea-level rise and decreasing sediment delivery, aligning with the core themes of proxy identification and process understanding in past and present interglacials.

How to cite: Corrado, G., Amato, V., De Santis, V., Gioia, D., and Aucelli, P.: Chrono-stratigraphy of Italian coastal dunes: implications for Holocene relative sea-level change and coastal progradation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20154, https://doi.org/10.5194/egusphere-egu26-20154, 2026.

This study investigates the coastal dune deposits of "Barrier III" along the southern Brazilian coast, and in particular along the coastal area close to Osório and Paranaguá. While traditionally attributed to the Marine Isotope Stage (MIS) 5e highstand, emerging evidence suggests this barrier is a complex system incorporating younger deposits from MIS 5a or even MIS 3. The analyzed sequences consist of aeolianites outcropping up to a few meters above present sea level. To ensure high-resolution spatial accuracy, proxy elevations were measured using a GNSS RTK station and referenced to the local geoid model (MAPGEO2015), maintaining a vertical error margin of a few centimeters.

Through geomorphological, granulometric, and morphoscopic analyses, this research re-evaluates the geochronological framework of these deposits by presenting 19 new Optically Stimulated Luminescence (OSL) ages. The findings address a critical scientific debate: while a broad consensus has long placed sea levels during MIS 5a and 5c several meters below present, recent studies increasingly suggest that sea level at that time may have been closer to, or even above, modern levels in certain regions. This study examines the extent to which eustatic oscillations during these substages, and potentially MIS 3, drove sedimentary dynamics capable of shaping dune systems in positions proximate to the modern shoreline.

How to cite: Cerrone, C., Lämmle, L., Scicchitano, G., Perez Filho, A., Chauveau, D., Dean, S., Georgiou, N., Leone, S., Jovane, L., Tagliaro, G., and Rovere, A.: Late Pleistocene coastal dynamics: Insights from new OSL Chronology of Barrier III aeolianites, Southern Brazil, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17729, https://doi.org/10.5194/egusphere-egu26-17729, 2026.

The İzmir–Dikili coast (NE Aegean Sea, Türkiye) is a key area for studying coastal evolution due to its complex geological, tectonic, and climatic setting.

Beachrocks are widely used as reliable proxies for reconstructing paleo-sea levels and constraining regional relative sea-level (RSL) changes. This study investigates submerged beachrocks and associated archaeological structures, documented for the first time along this coast, to reconstruct Holocene RSL evolution of the region.

We employed an integrated methodology including underwater observations, aerial photogrammetry, coring, petrographic analyses, and radiocarbon dating within a GIS framework. High-resolution bathymetry data revealed continuous submerged beachrock outcrops with a total length of approximately 3.5 km, situated at depths between 0.38 and 1.50 m below the present mean sea level. Petrographic analyses characterized these deposits as carbonate-cemented sandstones and conglomerates. Geomorphologically, the beachrocks exhibit both tabular and deformed block structures. Archaeological remains, such is reported to be a submerged pier, were also documented at compatible depths.

The distribution and depth of these indicators, combined with the regional geology demonstrate a Holocene RSL rise for the Dikili coast.  We interpret this trend as being primarily controlled by long-term subsidence of the Dikili Graben. Preliminary calculations suggest a rate of approximately 0.4 mm/yr, pending validation by ongoing radiocarbon dating.

This study establishes a robust framework for integrating geological, geomorphological, and archaeological indicators to investigate Holocene sea-level changes in tectonically active coastal settings. Our findings contribute new and critical data to the regional sea-level database of the Northern Aegean.

This study was supported by TUBITAK 1919B012462336 grant and Istanbul Technical University Research Fund, FLO-2025-47205.

How to cite: Onay, T., Burasoglu, S. F., Tulumen, E. B., Kahvecioglu, A. A., and Tari, U.: Holocene Relative Sea-Level Changes and Coastal Evolution Along the Izmir–Dikili Coast (NE Aegean Sea) Insights from Submerged Beachrocks and Archaeological Evidence, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9584, https://doi.org/10.5194/egusphere-egu26-9584, 2026.

Low-lying coastal estuaries, home for ~60% of the world’s population, are often dredged for navigation. Dredging deepens the estuary channel, hypothetically disturbing the hydro- and morpho-dynamics of an estuary. However, the impact of this activity on the morphological equilibrium state (i.e. balanced state between erosion and deposition) and flood propagation of the estuary leaves a substantial knowledge gap. As such, addressing this gap is fundamental to understanding the tendency of the estuary to bounce back to its morphological equilibrium state (i.e. which part severely needs more sediment), along with hydrodynamic impact on tidal and fluvial floods, especially under current sea-level rise (SLR) projections.

Here, high-resolution bathymetric data from 2016 to 2025 are used to detect morphological changes and to run 2D hydrodynamic simulations under varying tidal and fluvial flood conditions, added with 2100 SLR projection in the Clyde estuary, United Kingdom. In tidal prism theory, scaling between the tidal prism (P) and cross section area (A) represents a dynamic equilibrium state of feedback between tidal channel morphology and hydrodynamics. It is used here to understand the current equilibrium state of the uppermost, anthropogenically constrained part and unconfined, downstream part of the estuary.

In an equilibrium state, erosion and deposition in the system are in balance. Instead model shows that the Clyde estuary has been in a morphological disequilibrium state, during the entire study period. Dredging activity, type of flood, sea-level rise and channel confinement collectively affect the morphological equilibrium state of the Clyde estuary, with the channel confinement showing the most pronounced impact.  Dredging and flood type have a minor impact on the downstream morphological equilibrium of the Clyde. In contrast, dredging significantly disrupts the equilibrium of the fully confined upstream section. Although net accretion occurs throughout the system—most strongly in the upstream region—the annual sedimentation rate decreases by approximately a factor of sixteen from 2016-2025. This is because the current disequilibrium state tends to make the system to erode itself. What is the impact of this on flooding? Increased accretion upstream restricts the upstream propagation of the tidal flood, thereby reducing the overall extent of tidal inundation. However, the associated reduction in upstream cross-sectional area increases the extent of fluvial flooding. Under the 2100 SLR projection, assuming the same levels of dredging and estuary shape as today, the estuary gets closer to its morphological equilibrium state. As the sea-level rise delivers more water into the estuary, it increases both the tidal prism volume and the cross-sectional area. Lastly, channel confinement by riverbanks to protect the infrastructure and people from flooding, impacts morphological disequilibrium the most. Channel confinement laterally reduces the cross-section area, making the space available for the flowing water laterally limited and consequently the system adjusts vertically, making it more erosive and increases flood risk. Here we show that tidal prism theory could aid us in understanding the morphological equilibrium state of a dredged estuary, providing us with a useful guideline on sustainable sediment management and flood mitigation under the projected sea-level rise.

How to cite: Prasojo, O. A., Hurst, M. D., Williams, R. D., Naylor, L. A., and Toney, J. L.: Dredging impacts on morphological equilibrium and flood propagation in the Clyde estuary , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21315, https://doi.org/10.5194/egusphere-egu26-21315, 2026.

How to cite: Bonenkamp, M., Baar, A., Nienhuis, J., and Storms, J.: Effect of Variability in River Discharge and Sediment Supply  on Morphodynamic Timescales in Estuaries, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19026, https://doi.org/10.5194/egusphere-egu26-19026, 2026.

Macrotidal flats in coastal environments experience complex interactions among hydrodynamic and sedimentary processes and their morphodynamics have been increasingly modified by human activities over recent decades. Because human-driven disturbances in geomorphic evolution are reflected across a range of spatial and temporal scales, identifying the dominant controlling factors driving geomorphic changes is therefore essential for interpreting coastal morphodynamics and predicting future coastal evolution. However, these aspects remain poorly understood in macrotidal environments.

Two macrotidal flats on the west coast of Korea, the Donggeom and the Shinsi tidal flats, which have been heavily impacted by embankment construction and tidal-flat reclamation, were examined to identify the dominant controls on long-term morphodynamic responses to coastal development. Multi-source remote sensing data, including satellite and drone imagery, were used to quantify changes in tidal channel morphology, channel geometry, and surface bedform migration across seasonal to multi-decadal timescales (1975–2025). Seasonal to annual variations in grain-size distributions were analyzed using surface sediment samples to characterize sedimentary processes and surface sediment dynamics.  

The Donggeom tidal flat, developed within a deltaic setting with sustained fluvial sediment supply, exhibited increasing channel sinuosity and a transition toward a dendritic and narrower channel network, indicating progressive tidal-flat aggradation. In contrast, the Shinsi tidal flat, which lacks a direct fluvial sediment source, experienced tidal-channel development accompanied by seaward sediment export. Annual grain-size variations indicate that embankment construction enhanced wave exposure and promoted coarser sediment deposition, suggesting intensified sediment reworking and erosion. The contrasting geomorphic responses to coastal development are primarily attributed to differences in sediment availability and local hydrodynamic conditions. These results highlight sediment supply and geomorphic configuration as key controls on the spatial variability of macrotidal flat evolution subjected to long-term human modification.

How to cite: Jo, J., Choi, K., Bang, S., and Park, J.: Long-term geomorphodynamic responses of macrotidal flats to human modification (1975-2025), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17153, https://doi.org/10.5194/egusphere-egu26-17153, 2026.

Deltas are among the most dynamic and productive landscapes on Earth, shaped by the continuous interaction between physical processes such as river discharge, tides, waves, wind, sediment transport, and biological processes driven by vegetation, benthic organisms, and microbial activity. This interplay, central to the field of biogeomorphology, has built and shaped delta’s worldwide across spatial and temporal scales. In the context of accelerating climate change, sea-level rise, land subsidence, and increasing human intervention, it becomes increasingly important to understand how biological and physical processes interact in deltas. This knowledge is crucial for predicting how resilient deltas are, recognizing when critical changes may occur, and developing effective adaptation strategies.

Delta systems change through interacting physical and biological processes that occur under both normal conditions and extreme events such as floods, storms, and droughts. Organisms can stabilize sediments, modify water flow, and affect erosion and deposition, while changes in landform shape can also create or eliminate habitats. Despite their importance, these processes remain insufficiently quantified, particularly at the scale of an entire delta and during extreme events, due to limitations in long term and integrated observations. Bridging this knowledge gap requires coordinated monitoring that captures slow trends, sudden disturbances, and their cumulative impacts across rivers, estuaries, and coastal dune systems.

Delta-ENIGMA is a new large-scale research infrastructure in the Dutch Rhine-Meuse-Scheldt delta aimed at transforming and advancing the study of biogeomorphology and delta dynamics. Over a 10-year period (2023-2032), Delta-ENIGMA forms a coherent observation network across key sites in rivers, estuaries, beaches, and dunes, designed to systematically measure interactions between organisms, hydrodynamics, sediment transport, and morphology under both normal and extreme conditions.

Central to this effort is the deployment of state-of-the-art field instrumentation, including high-resolution 3D laser scanners, multibeam echosounders, submerged flow and sediment sensors, wave recorders, phenocams and multispectral drones. These measurements are complemented by targeted observations during extreme events, enabling the capture of high-impact processes that may strongly influence long-term delta evolution. In parallel, Delta-ENIGMA upgrades and develops laboratory facilities such as wind tunnels, mesocosm systems, and advanced bio-morphodynamic flumes to experimentally investigate processes that are difficult or impossible to observe directly in the field but are relevant under future climate scenarios.

To maximize scientific and societal impact, Delta-ENIGMA integrates its observational and experimental facilities within an open, federated data infrastructure and a dedicated knowledge interaction platform. A uniform open-source package will be developed with which data from all Delta-ENIGMA instruments can be read out, quality-controlled, documented with metadata, packaged in uniform data structures, and uploaded to central storage.

Together, these facilities provide researchers and policymakers with unprecedented access to high-quality data, experimental capabilities, and collaborative environments. By linking fundamental biogeomorphological understanding to applied research and innovation, Delta-ENIGMA establishes the Dutch delta as an international super site that is open to researchers internationally for studying delta dynamics and supporting the development of robust, science-based strategies for climate adaptation and sustainable delta management.

How to cite: Ruessink, G., Dutta, S., and Middelkoop, H.: Delta-ENIGMA: advancing biogeomorphology research in deltas through observation and experimentation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16989, https://doi.org/10.5194/egusphere-egu26-16989, 2026.

Vegetation growth in coastal environments, such as estuaries and deltas, plays an important role in coastal morphology. Gridded hydrodynamic and morphodynamic models typically have options to incorporate constant vegetation effects via a roughness parameter, where taller and denser vegetation is associated with higher roughness that alters flow velocities and sediment transport. In this study we present DYCOVE (DYnamic COastal VEgetation): a flexible, open-source model that couples with physics-based, hydro-(morpho)dynamic models to simulate life-cycle dynamics (colonization, growth, and mortality) of multiple vegetation species in coastal environments. Via interactive coupling, changes in vegetation state provide spatial and temporal updates of friction effects in the physics-based model, creating a dynamic feedback loop. However, vegetation colonization, growth, and mortality depend on accurate modeling of local inundation, flow speeds, and bed level changes, which can be strongly dependent on model grid resolution. Finer grid sizes resolve these physical processes more accurately but are not always feasible due to computational demand, whereas coarser grids may result in topographic smoothing that distorts the hydrodynamic solution. Since vegetation depends on reasonable accuracy of physical processes, any errors in hydrodynamic predictions will affect the vegetation calculations, resulting in potentially compounding errors over several iterations. Using DYCOVE, we quantify errors caused by grid resolution effects and evaluate produced differences in vegetation distributions compared to observations from the Wax Lake Delta in Louisiana, USA. Lastly, we discuss strategies for overcoming limitations and errors related to grid resolution that allow for accurate and efficient prediction of vegetation species cover in coastal environments.

How to cite: Tull, N., Brückner, M., and Passalacqua, P.: Quantifying the compounding effects of grid resolution to improve vegetation predictions in delta models, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8343, https://doi.org/10.5194/egusphere-egu26-8343, 2026.

Abstract

Salt marshes are key components of coastal and estuarine landscapes, providing important ecosystem services including carbon storage, nutrient filtering, and wave attenuation. Currently, marsh sustainability is increasingly threatened by sea-level rise and human pressures such as land reclamation, subsidence, and reduced sediment supply, leading to widespread and accelerating marsh loss worldwide.

Understanding salt-marsh evolution at relevant timescales typically relies on biogeomorphodynamic models that resolve hydrodynamics, sediment transport, and morphological change, coupled with biotic feedbacks from vegetation, which directly affect sediment transport and organic deposition. Vegetation dynamics in these models are commonly based on the assumption that each species has an optimal elevation range where its productivity peaks. This assumption derives from field observations of realized (i.e., observed) ecological niches, which display hump-shaped distributions along marsh elevation gradients.

However, both theoretical and empirical insights now challenge this hypothesis, suggesting that species productivity actually tends to increase monotonically with elevation—following a logistic growth pattern—and that the hump-shaped niches observed in the field are merely the result of interspecific competition. This discrepancy challenges the way vegetation feedbacks are represented in most salt-marsh models and calls for a re-evaluation of how species interactions are incorporated into predictions of marsh evolution.

Here we use a biogeomorphodynamic model that solves hydrodynamics, sediment transport, sediment mass balance, and topographic change, coupled to two alternative vegetation formulations: (i) a classical model based on hump-shaped elevation niches, and (ii) a spatially explicit dispersal–competition model based on monotonic (logistic) fundamental niches. Simulations are performed for a real case study in the Venice Lagoon under different rates of relative sea-level rise and suspended sediment supply.

The two vegetation formulations produce markedly different patterns of vegetation zonation and, more importantly, contrasting predictions of marsh resilience to rising sea levels. While the classical model predicts marsh persistence under a relative sea-level rise of 2.5 mm yr⁻¹, the dispersal-based vegetation model predicts marsh degradation, yielding qualitatively different outcomes under the same environmental forcings.

By explicitly accounting for dispersal and interspecific competition, our results show that vegetation dynamics exert a stronger control on long-term marsh survival than is captured by traditional niche-based models. This calls for a revision of current biogeomorphodynamic frameworks to improve projections of salt-marsh resilience under future sea-level rise.

Keywords: Echo-morphodynamic model, Dispersal colonization, Habitat quality, Sediment transport, Salt marsh

How to cite: Shamsnia, H., Finotello, A., D'Alpaos, A., and Bertuzzo, E.: A Comparative Study of Salt Marsh Vegetation Dynamics in an Eco-Morphodynamic Modeling Framework, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18985, https://doi.org/10.5194/egusphere-egu26-18985, 2026.

Crevasse splays generated by natural levee breaches are key geomorphodynamic mechanisms through which rivers deliver sediment to adjacent floodplains and lagoons, promoting land building and wetland development. In heavily engineered deltaic systems, such features provide valuable natural analogues for nature-based solutions (NbS) aimed at restoring sediment connectivity and enhancing coastal resilience. This study investigates the recent morphodynamic evolution of a crevasse splay in the Batteria Island, Po River Delta, formed due to a natural levee breach, with the aim of quantifying rates of splay growth, surface accretion, and channel-network dynamics.

The evolution of the splay between 2015 and 2024 was reconstructed using Sentinel-2 Satellite Imagery. Changes in vegetation cover, tidal-flat extent, and distributary channel patterns were mapped from true- and false-colour composites, while rates of splay-front progradation were quantified using DSAS. High-resolution surface morphology was further constrained using two drone-based LiDAR surveys (2024 and 2025), complemented by a bathymetric survey.

Sedimentological data from approximately 30 shallow sediment cores distributed across the splay were used to constrain vertical and lateral variability within the deposit and to generate a three-dimensional subsurface model of the splay’s internal architecture.

Results show self-sustained growth of the crevasse splay into the lagoon, accompanied by a gradual expansion of vegetated salt-marsh surfaces and net positive vertical accretion. Progradation rates decrease slowly over time due to geometric spreading of sediment across the widening splay lobes. The distributary channel network exhibits distinct dynamics: three main channels remain consistently open, whereas secondary channels are frequently abandoned after becoming blocked by plant debris. These abandoned channels are subsequently colonized by vegetation, promoting sediment trapping and stabilizing the splay surface. In the northern part of the splay, newly formed lobes are beginning to be colonized by vegetation, but the process remains slow, indicating a lag between sediment deposition and ecological succession.

The Batteria Lagoon crevasse splay demonstrates how naturally occurring levee breaches can rapidly create and stabilize new wetland surfaces in a tide-influenced delta. These findings highlight the geomorphic effectiveness of levee-breach-driven sediment delivery and provide quantitative insights relevant to the design and assessment of NbS-based wetland restoration strategies in deltaic environments.

How to cite: Mandal, A. R., Rossi, V. M., Finotello, A., Ghinassi, M., Irace, A., Zaggia, L., Berton, A., Trifiró, S., Mantovani, M., and Cosma, M.: Architecture and evolution of crevasse splay in Po River Delta: implications for nature-based wetland restoration, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19497, https://doi.org/10.5194/egusphere-egu26-19497, 2026.

Many deltas and lagoonal systems are currently under threat of continued sea level rise and face potential future drowning, or transgression of the sea, particularly in lowland lagoonal areas. Resulting drowning of deltas and the impact of potential mitigation measures is subject of many studies. However, timescales and spatial complexity of transgression-related processes often remain unknown or topic of debate. Transgression-forced vegetation changes, salinization, changed these processes are fundamental  for the functioning of the lagoonal complex, determining the stability of tidal inlets and rate of sediment transport. Reconstruction of coastal transitions in the past can quantify rates of change and coastal morphology, which by comparison with model simulations help to constrain the transgressive processes and effects.

The former Caorle lagoon, located in the Veneto region in NE Italy, is currently mostly reclaimed agricultural land. It is under threat of sea-level rise and the past development of this relatively small area acts as a natural laboratory of coastal change, highly relevant for the adjacent lagoon of Venice. We use the output of years of fieldwork (2012 – 2026), a large set of radiocarbon dates derived and proxy records at selected core sites of pollen and foraminifera to constrain salinity gradients, ecological changes and human influence. Exceptionally large infill rates are found in unstable tidal inlets. We find that deposition rates at sites with stable conditions vary between 1-8 mm/yr and are largest in depressed areas (incised valleys) and during rapid sea level rise. Lastly, we find that landscape transitions from fluvial- to tide dominated can be rapid (10 – 100 years) or gradual (100 – 1000 years) depending on relative height, topographic position and river configuration.

How to cite: Gerats, W.: Constraining the past and future evolution of a drowning landscape in Northeastern Italy, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21823, https://doi.org/10.5194/egusphere-egu26-21823, 2026.

Developed estuarine and lagoonal systems have progressively evolved toward increasing human control, as their morphology and hydrodynamics have been modified to support settlements, infrastructure, and economic activities. As climate change drives sea-level rise and alters hydrological and meteorological extremes, this human-dominated trajectory is accelerating, with hard-engineering flood-defence systems—including levees, river diversions, and storm-surge barriers—becoming central to coastal flood-risk management in urbanized coastal areas. While the hydro-, morpho-, and ecological effects of individual flood-protection measures are relatively well documented, far less is known about how multiple defenses interact when they operate simultaneously within the same estuarine system.

Here, we investigate the Venice Lagoon (Italy), a paradigmatic anthropogenic tidal basin shaped by centuries of human interventions. In the northern lagoon, a river-levee spillway is used to divert excess river discharge toward the lagoon to protect mainland urban areas from fluvial flooding, while a storm-surge barrier system at the lagoon inlets is operated to limit marine flooding in Venice and other lagoonal settlements. Using numerical modeling supported by field data, we analysed lagoon hydrodynamics during November 2019, a period characterized by exceptional rainfall and storm-surge conditions that triggered repeated spillway operations and severe flooding in Venice. We compared scenarios with and without storm-surge barrier closures and evaluated the effects of projected sea-level rise over a 40-year horizon.

Our results show that storm-surge barrier closures, although effective at reducing tidal water levels within the lagoon, intensify the freshening caused by riverine flood inputs by restricting tidal exchange and increasing hydraulic heads at (and thus flow discharge through) the spillway. Under sea-level-rise scenarios, barrier closures are projected to become both more frequent and longer-lasting, leading to greater volumes of freshwater entering the lagoon and to an expansion of areas affected by altered salinity. Over longer timescales, these coupled processes are expected to drive the lagoon away from its present hydrodynamic and ecological regime, increasing its reliance on active human regulation to maintain stability. This highlights the need for integrated adaptation strategies that explicitly account for interactions among flood-defence infrastructures, so that coastal cities can be protected without undermining the resilience of estuarine ecosystems under ongoing climate change and intensifying anthropogenic pressures.

How to cite: Michielotto, A., Finotello, A., Matticchio, B., Tognin, D., Mel, R. A., Feola, A., Viero, D. P., Carniello, L., and D'Alpaos, A.: Urban Flood Prevention and Ecosystem Trade-offs in Venice, Italy, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17730, https://doi.org/10.5194/egusphere-egu26-17730, 2026.