Coastal monitoring is a rapidly evolving field essential for understanding meteorological and marine conditions, which in turn supports the development of effective strategies for managing coastal areas. This necessity is increasingly critical given the challenges posed by climate change, rising sea levels, and extreme weather events. Among the tools available, video surveillance, combined with advanced machine learning and computer vision techniques, has emerged as a powerful method. It offers detailed spatial and temporal data, essential for analyzing tidal phases, wave parameters, and storm dynamics across extensive geographic areas.

In this study, we propose an innovative integration of optical flow techniques with video analysis to accurately quantify wave motion parameters. Optical flow, which evaluates object displacement between video frames, is applied to determine wavelength, wave height, and flow velocity. This approach is particularly suited for storm conditions where traditional methods face logistical and financial constraints. Our method enables high-precision, real-time measurements vital for analyzing coastal processes during extreme events. To ensure reliability, the results are cross-validated with in situ instrument data and verified through environmental reconstructions using point clouds and ground control points. This dual-validation strategy minimizes video distortions and enhances measurement accuracy, aligning optical flow results with physical realities.

The proposed system has been tested in a controlled environment at the Coastal Engineering Laboratory of the University of Palermo. A two-dimensional laboratory flume simulated different coastal conditions, ranging from calm waters to storm-like scenarios, ensuring the robustness and adaptability of the methodology. By leveraging optical flow techniques with video surveillance, this approach promises a transformative impact on coastal monitoring, providing continuous, automated, and cost-effective data collection even in remote or inaccessible locations. It offers a scalable alternative to conventional methods, which often demand expensive installations and extensive manpower. The potential of this method to deliver high-quality real-time data, represent a significant advancement in coastal management and environmental monitoring.

How to cite: Sabato, G., Scardino, G., Kushabaha, A., Ciraolo, G., Scala, P., Manno, G., and Scicchitano, G.: Optical Flow for Wave Characterization in a 2D Water Flume Using Video Analysis: A Cutting-Edge Tool for Coastal Monitoring, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-424, https://doi.org/10.5194/egusphere-egu25-424, 2025.

Coastal boulder deposits (CBD) are geomorphic signatures of past extreme wave events (EWEs) such as storms and tsunamis. CBD can be used to reconstruct EWEs if the link between local wave climatology and boulder transport is understood. This proxy of wave data is important for building records in regions where wave data are sparse and for coastal hazard management. This study is focused on storm-driven coastal boulder transport along the west coast of Ireland.

We monitored coastal boulder motion at four sites on Inishmaan, Ireland over two winters (2022/23 and 2023/24). We manually relocated most study boulders to supra-tidal positions closer to the shoreline where they were more likely to be mobilized during storms. The boulders were instrumented with accelerometers to capture the timing of orientation changes, while pressure sensors were deployed on the supratidal platforms to record onshore wave conditions. Site characterization and distance measurements were conducted using uncrewed aerial vehicles (UAVs) for Structure-from-Motion (SfM) processing to create Digital Terrain Models (DTMs). Additionally, traditional ground surveys—measuring boulder axes and GPS locations—were augmented with iPhone LiDAR to estimate boulder volumes. Other methods included, 3D printing for sensor housing and Apple Airtags for boulder tracking.

Our results indicate that boulder transport occurs almost exclusively during storm events coinciding with high tide. We also found that transport was more likely for boulders on low-roughness platforms compared to those constrained by geomorphic features such as grykes, boulder ridges, or platform steps.

Our findings suggest that some boulders are mobilized annually, with isolated boulders being particularly susceptible to storm-driven transport. These results have implications for interpreting preservation potential in the context of coastal hazard assessments. Ongoing numerical modeling will enhance our understanding of regional wave climatology associated with these transport events.

How to cite: Spero, H., Bourke, M., Berke, M., Cullen, N., Herterich, J., Westerink, J., Tejaswi, A., and Kennedy, A.: Annual Mobility of Coastal Boulder Deposits During Storm Events: Inishmaan, Ireland, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2017, https://doi.org/10.5194/egusphere-egu25-2017, 2025.

The Arctic is warming nearly four times faster than the globe. The drastic consequences of climate change are observed in high mountain areas located within the Arctic coast. This is where permafrost degradation and slope destabilization occur, which can be a direct cause of large-scale landslides. Masses of soil, rocks and sediments reaching the coast cause the formation of tsunami waves, which, reaching the other side of the fjord or strait, destroy infrastructure or affect the development of the coastal zone. An example of this is the Vaigat Strait in western Greenland, where tsunami waves have been observed for several decades. In the last dozen years, the intensity of this phenomenon has increased, which was a direct consequence of, among others, the destruction and displacement of the town of Qullissat on Disko Island. The research in the GLAVE project attempted to read the record in sediments located in areas flooded by tsunami waves. For this purpose, the commonly known GPR method was used, but with the use of a modern GPR set consist of the Mala Ground Explorer and 450 MHz shielded antenna, which provides high-resolution radar data. The 2D/3D profiles were supplemented with information from trenches and shallow boreholes made at the intersection of the profile lines. Preliminary results indicate that each tsunami wave reaching the opposite coasts of the Vaigat Strait leaves behind evidence in the form of specific sedimentological structures. The interpretation of the obtained new GPR data supported by information from possible dating can indicate contemporary and historical tsunami episodes. The conducted GPR studies can support landslide monitoring conducted in threatened areas and more accurately predict the threat from the occurrence of sudden tsunami waves to the environment and the local community.

How to cite: Senderak, K., Sobczyk, A., Kasprzak, M., Szczypińska, M., Kostrzewa, O., and Strzelecki, M.: Reflection of landslide tsunami in sediment structures: the new GPR data from coastal zone of the Vaigat Strait, West Greenland, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6178, https://doi.org/10.5194/egusphere-egu25-6178, 2025.

The impact of extreme wave events, such as hurricanes and tsunamis, has resulted in the displacement of large coastal boulders along various coastlines worldwide. Several coastal boulders have been studied along the Mediterranean coasts to assess the wave flow capable of causing their dislodgment. In particular, recent extreme wave events, primarily associated with the occurrence of Mediterranean hurricanes, have led to the dislodgment of multiple boulders under different pre-setting transport conditions (subaerial/submerged, joint-bonded, cliff-edge). These movements have been recorded by surveillance cameras located along the coasts, providing direct evidence of boulder displacements under well-defined transport conditions. A detailed understanding of the pre-setting transport conditions and types of movements (sliding, overturning, saltation) is crucial for evaluating the theoretical wave flow needed to initiate boulder transport. In this study, a comparison was performed between theoretical wave flow and computed wave flow, utilizing numerical models of incipient motion formulas along with the recorded data obtained through computer vision techniques. Morpho-topographic surveys were conducted at different times on a rocky coast in southeastern Sicily (Italy), which experienced boulder dislodgments during various impacts of Mediterranean hurricanes. Terrestrial Laser Scanning (TLS) and Structure from Motion (SfM) techniques were used to assess the dimensional parameters of the coastal boulders. Subsequently, numerical models based on incipient motion formulas were applied to determine the theoretical wave flow required to initiate boulder movement. To compute the wave flow impacting during a given storm event, we applied computer vision techniques to analyze video recordings from surveillance cameras that captured the moments of boulder movement. The video recordings were automatically georeferenced using Ground Control Points extracted from TLS and SfM data to obtain a planar view of the wave propagation with adjusted perspective wrapping. Optical Flow was then applied to the georeferenced video recordings in order to compute the wave flow during these movements. The comparison between computed and theoretical flow provided useful insights for sensitivity analysis of friction, drag, and lift coefficients, thereby improving the accuracy of the force assessments in the incipient motion formulas.

How to cite: Scardino, G., Nandasena, N. A. K., and Scicchitano, G.: The computer vision techniques and numerical models for the assessment of wave flow during coastal boulder movements, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3076, https://doi.org/10.5194/egusphere-egu25-3076, 2025.

Sedimentary ancient DNA (sedDNA) is emerging as a powerful tool for studying storm and tsunami deposits, offering novel insights into past events and their ecological impacts. By analyzing sedDNA from microbial communities preserved in known tsunami and storm-deposited sediments, researchers can distinguish between these deposits and non-overwash sediments. This method has been successfully applied to sites impacted by the Palu tsunami in 2018, where we distinguish between tsunami and non-tsunami deposits in different geological settings and to the deposits of the 2004 Indian Ocean Tsunami and subsequent storm events, demonstrating significant differences in microbial communities (Yap et al., 2021). Despite challenges related to sample preservation and data interpretation, the integration of sedDNA with traditional methods holds promise for enhancing our understanding of sedimentary processes and ecological shifts associated with catastrophic natural events. Combining sedDNA with traditional sediment analysis can provide a more comprehensive understanding of past environmental events. Furthermore, sedDNA has shown potential longevity in tsunami deposits (Yap et al., 2023), preserving microbial community signatures for up to several millennia.

Yap, W., Switzer, A. D., Gouramanis, C., Marzinelli, E., Wijaya, W., Yan, Y. T., ... & Lauro, F. M. (2021). Environmental DNA signatures distinguish between tsunami and storm deposition in overwash sand. Communications Earth & Environment, 2(1), 129.

Yap, W., Switzer, A. D., Gouramanis, C., Horton, B. P., Marzinelli, E. M., Wijaya, W., ... & Lauro, F. M. (2023). Investigating geological records of tsunamis in Western Thailand with environmental DNA. Marine Geology, 457, 106989.

How to cite: Switzer, A., Yap, W., Lauro, F., and Majewski, J.: Unlocking the Secrets of Past Coastal Catastrophes : Using sedimentary ancient DNA (sedDNA) to investigate Storm and Tsunami Deposits, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7829, https://doi.org/10.5194/egusphere-egu25-7829, 2025.

Coastal boulders have been identified as significant markers for the assessment of extreme wave conditions and forces in past events, thus providing crucial insights into the dynamics of coastal hazards. This study examined a coastal boulder field located near Pounta in the Gulf of Laconia (Southern Peloponnese, Greece). The boulders were studied in terms of their lithology, geometrical shape, distribution by UAV imagery, and axis orientation along the coast. 3D LiDAR measurements in combination with rock density analysis were carried out to calculate their masses. The investigation was achieved through open-access methodologies, encompassing readily accessible LiDAR recording technology, with the objective of substantiating the replicability of such studies. An essential aspect of the study involved the detailed specification of previously published data for the region, providing correct locations and characteristics of the boulders, besides employing high-resolution field data and refined analytical techniques for the estimation of wave heights and velocities.

We mapped and analyzed >250 boulders along a ~600 m-long coastal stretch with the furthest inland boulders being located at ~200 m at 6-7 m asl. Boulders were imbricated and show overturning marks (e.g., rock pools) indicating transport during an extreme wave event. Some boulders are deposited on the bedrock, while further inland located boulders are partly embedded in sand-grade sediments, indicating joint transport and deposition of boulders and sediments. Preliminary results from UAV mapping show grouping of boulders based on differences in size and potentially by different events (e.g., AD 1303 Crete earthquake). The largest imbricated boulders (~3.3 t) have been moved a few meters inland, while smaller boulders (up to several hundred kilograms) were transported further inland.

With reference to the existing literature, we found that the volume analyses carried out overestimated the masses of the coastal boulders, thus calculated wave energies to transport or even move boulders were erroneous. We updated existing mathematical approaches to calculate the properties of the waves transporting the analyzed boulders by adding the properties of the transport medium itself that sets the boulder in motion. An approach to take this into account is implemented here for the calculation, accordingly affecting the studied wave energies of historic high-energy events (i.e., storm surges or tsunami).

The study area is characterized by complex coastal geomorphology by staircase-like raised marine terraces, which is susceptible to effects brought by sea-level rise and is particularly sensitive to hazards triggered by extreme wave events. The absence of protective infrastructure in this area necessitates the crucial role of studies that investigate the potential hazard of extreme wave events in coastal risk assessment.

How to cite: Louis, K. J., Bellanova, P., Justen, S., Kautz, G., Houbertz, S., Arianoutsou, A., Papanikolau, I., and Reicherter, K.: Coastal Hazard Assessment through 3D Mesh Analysis of Coastal Boulder Deposits from Extreme Wave Events in Greece, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19938, https://doi.org/10.5194/egusphere-egu25-19938, 2025.

Extreme meteorological events, such as medicanes, are increasingly recognized as key drivers of geomorphic transformation along rocky coastlines. This study explores the response of coastal boulder deposits in Malta to Medicane Helios, focusing on detachment, displacement, and the role of localized geomorphic vulnerabilities.

Medicane Helios, originating over the North African coast, intensified as it traversed the central Mediterranean, reaching Malta on February 9–10, 2023. Its passage was marked by torrential rainfall, gale-force winds, and intense wave energy that reshaped the coastal landscape. While studies often generalize the effects of such storms, this research emphasizes micro-scale interactions between wave energy and specific geomorphic features, including solution hollows and structural joints.

Field observations and aerial surveys using unmanned aerial vehicles (UAVs) were conducted pre- and post-event, providing data for 3D terrain models. The analysis revealed significant movement of boulders, including rotational displacement and intertidal reconfiguration, previously unreported during other extreme events in the region. The findings highlight not just the physical redistribution of clasts but also newly exposed erosional features, such as abrasion marks and scree accumulations.

By drawing parallels with other medicanes, the study underscores the increasing vulnerability of Mediterranean coastal zones to intensified storm impacts. These results emphasize the necessity of integrating localized geomorphic assessments with broader climate models to develop effective coastal defence strategies. The outcomes have broader implications for understanding the resilience of coastal systems to future climatic stressors.

How to cite: Gauci, R., Causon Deguara, J., and Inkpen, R.: The role and impact of medicanes on coastal boulder dynamics:  a preliminary case-study from the Maltese Islands. , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19371, https://doi.org/10.5194/egusphere-egu25-19371, 2025.

The northwestern coast of Sal Island, Cape Verde Archipelago, features an almost continuous rocky shoreline, regularly impacted by powerful Atlantic waves exceeding 4 meters in height and 20 seconds in period. The most striking geomorphic feature of this coast is a prominent boulder ridge perched atop the rocky cliff, situated 10 to 15 meters above sea level and extending 80 to 100 meters inland. The ridge contains boulders with diameters exceeding two meters, raising intriguing questions about its origin: Is the boulder ridge a product of modern wave action? Was it formed during the Last Interglacial, when relative sea levels were 4–8 meters higher than today? Or does it record a single, catastrophic tsunami event? To address these questions, we conducted high-resolution topographic mapping using Unmanned Aerial Vehicles (UAVs). This topographic data was used as a base for hydrodynamic modeling with XBeach. The modeled flow velocities were compared against the location and elevation of the boulder ridge, while the highest flow velocities were cross-validated with empirical equations of incipient motion for the largest boulders in the area. 

This presentation is a contribution to the WARMCOASTS project, which has received funding from the European Research Council under the European Union's Horizon 2020 research and innovation programme (grant agreement n. 802414)

How to cite: Rovere, A., Ramalho, R. S., Casella, E., Vieira, G., Barile, C., Scardino, G., Nandasena, N. A., and Scicchitano, G.: Boulder ridges in Sal Island, Cape Verde: imprint of tsunamis, modern storms, or Last Interglacial wave deposits?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5613, https://doi.org/10.5194/egusphere-egu25-5613, 2025.

This paper provides a detailed study of coastal boulder deposits (CBD's) that were recently discovered along the southern Istrian coasts at Premantura, and on the nearby islet of Fenoliga. Additional observations have also identified CBD's at the Brijuni archipelago 20 km's to the northwest. The northern Adriatic Sea is a semi-enclosed basin, limiting the number of storm wave capable of the detachment, transport, and deposition of large boulders. However, despite this constraint extensive CBD's are evident.

A multidisciplinary approach was used to investigate the sites including geological and geomorphological surveys, together with the use of an Uncrewed Aerial Vehicle (UAV), digital photogrammetric analysis and swim surveys. Measurements of boulder position, elevation, size, shape and density were carried out recently at the two sites. 

We recognized and mapped approximately 950 clasts at Premantura and 592 clasts at Fenoliga. At Brijuni several observations have identified that some blocks periodically appear and disappear following severe storm events. Furthermore, we carried out multitemporal monitoring activities at the Premantura test site, identifying the movement of a dozen of blocks primarily during the extreme low pressure Mediterranean storm Vaia in 2018.

Biogenic marine carbonate encrustations observed on 14 boulders in Premantura suggest the infra- and sublittoral zones as source areas, while for other boulders a subaerial origin is hypothesised. Local topography, together with the stratified limestone bedding planes and dense joint pattern constitute the predisposing factors for boulder size and detachment.

How to cite: Devoto, S., Ceccotto, F., Corradetti, A., Hastewell, L., Mantovani, M., and Furlani, S.: A multidisciplinary approach for the investigation of coastal boulder deposits in southern Istria (north Croatia), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7064, https://doi.org/10.5194/egusphere-egu25-7064, 2025.

The Japanese archipelago has been subjected to the threat of tsunamis throughout the Holocene. The catastrophic 2011 Tohoku-oki tsunami demonstrated that tsunami hazard assessment in Japan was underestimated, i.e. in wave heights and inundation depths. Paleotsunami studies can provide a deeper understanding of historical tsunami events and deliver crucial information about the frequency, magnitude, and characteristics of past tsunamis, enabling better preparedness for future events. This study focuses on the eastern coast of Hokkaido in the Tokachi region, an area with documented historical tsunami impacts (such as from the Tokachi-oki earthquakes in 1843 CE, 1952 CE, and 2003 CE).

We analyzed 1.5 m-long sediment profiles using an integrated approach combining sedimentological and organic geochemical analyses. At least five distinct tsunami deposits were identified in the stratigraphy and preliminarily dated by volcanic ashes of Mount Tarumae volcanic eruptions, e.g., the 1739 CE (Ta-a), the 1667 CE (Ta-b) and the 2500 cal. BP (Ta-c). These deposits are characterized by distinct sand layers that exhibit landward thinning patterns typical of tsunami deposits intercalated with peats. The application of organic geochemical proxies (e.g., n-alkanes, fatty acids, polycyclic aromatic hydrocarbons and hopanes) allows us to trace tsunami inundation beyond the sand deposits, providing a more comprehensive understanding of the depositional characteristics of these paleotsunamis and the contents of organics.

Our findings contribute to a more comprehensive understanding of the maximum inland extent of these paleotsunamis and demonstrate the effectiveness of multi-proxy approaches in identifying and characterizing these events. This research enhances our understanding of tsunami recurrence intervals, sediment transport processes and inundation patterns along the eastern Hokkaido coast, providing valuable input for regional tsunami hazard assessments and coastal management strategies.

How to cite: Decker, J., Bellanova, P., Nishimura, Y., Schwarzbauer, J., and Reicherter, K.: Paleotsunami deposits from coastal sediments in Hokkaido, Japan, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19749, https://doi.org/10.5194/egusphere-egu25-19749, 2025.

Climate change and sea-level rise are crucial global effects in the coming decades. This study aims to estimate the future effects of sea storms on low-lying coastal areas, by using an integrated approach using advanced modeling tools and technologies that include in the analysis the anthropic impacts and coastal subsidence. The approach wants to analyze past storm surges, sea level changes, and shoreline displacements to model future coastal variations due to the increasing frequency and magnitude of extreme events related to climate change.

We focus on the Volturno coastal plain, which is one of the largest and most populated coastal areas along the mid-Tyrrhenian Sea in Italy. The area is mostly exposed to meteo-marine forcings in the sector between 180° and 280° N, therefore major storm surges registered by the nearby National Network’s wave buoy were analyzed for this sector, to evaluate the coastal effect of the main flooding that occurred in the last 35 years. Peak Over Threshold methodology was used for this evaluation by considering events with a minimum significant wave height greater than 1,50 meters and a minimum duration of 12 hours. The selected storms were then divided into 5 categories, based on their power index (Dolan R., Davis R.E., 1992). Numerical simulations of two storms for each category were carried out on a coastal sector with high social, touristic, and naturalistic values, between the Volturno and Regi Lagni rivers. The topographic base used for hydrodynamic modeling has been extracted by analyzing a set of LiDAR surveys collected by the Italian Ministry of the Environment at 2 m of resolution. The elevation data have been converted into the RDN2008/UTM 32-33 coordinate system above sea level elevation (geoid-related height) to create a revised DEM of the coastal zone, validated through multiple GPS surveys carried out in 2024. The DEM of the underwater coastal sector was created by interpolating data from a single beam survey.

The calculation of the shoreline displacement rates shows that during 1954-2003, the coastal sectors of the Volturno River mouth retreated at a velocity >10 m/y. After 2004, thanks to the construction of two submerged breakwaters, this trend inverted with a total accretion of the beach of about 100 meters in 20 years. Nevertheless, the hydrodynamic simulation results allowed the estimation of flooded areas, also considering the three more probable IPCC–AR6 predictive scenarios of sea level rise until 2150. Storms with a return time of 10–25 years reach the dune toe for 80% of the total length. In the sector protected by the breakwater, such events tend to overtop the dune flooding the back dune system area which is part of the WWF natural reserve “Oasi dei Variconi”. According to our procedure, in the future, with a sea-level rise to 1.1 m, not only will such effects increase, but also their return period will be reduced to 5-20 years. Finally, the extreme event that occurred in 1999 will shorten its return period from 50 to 25-30 years.

How to cite: Fasciglione, G., Benassai, G., Di Luccio, D., Florio, A., Mattei, G., Mucerino, L., Trippanera, D., Aucelli, P. P. C., and Anzidei, M.: Erosive effects of sea-storms, human pressure, and sea level rise on Volturno coastal plain (mid-Tyrrhenian area): present to future coastal hazard, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11116, https://doi.org/10.5194/egusphere-egu25-11116, 2025.