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The Maltese archipelago is renowned for its spectacular coasts, characterized by vertical cliffs and scree slopes. In the western sector of Malta and the eastern region of Gozo, a marly clay formation with ductile properties underlying a stiff limestone unit has led to relevant lateral spreading. Utilizing drone aerial photogrammetry, digital elevation models, and satellite imagery, we analyzed the ongoing geomorphological processes across five promontories, selected as case studies. Our analysis reveals a complex interaction between geological structures, Quaternary sea level fluctuations, and lateral spreading processes. Photogrammetric models show that once detached, blocks from the plateaus tend to topple and fall or experience subsidence and backtilting. At Rdum il-Qammieħ, fractures up to 250 m long and openings of up to 2 m were observed, while at Sopu, detached blocks exhibit subsidence of up to 50% and rotations nearing 60°. In all the studied promontories, rotational slides predominantly occur at the frontal sectors, while toppling mechanisms are more common along scarp-edged plateaus. The thickness ratio between the stiff and the ductile formation, ranging from 0.13 to 1.12, along with slope gradients between 10° and 41°, further influence the stability of these coastal features. We discuss the structural and sea level influences on Maltese coastal cliff development over the last 125 ky. We propose a conceptual model outlining the evolution of the Malta Graben promontories through a three-stage evolutionary model: proto-promontories, cliff demolition, and isolation. This model emphasizes the significant role of predisposing, preparatory, and triggering factors in the geomorphological evolution of the Maltese coastline. Our findings provide essential insights into the landscape changes in the Maltese archipelago and represent a useful tool for coastal management and hazard mitigation strategies. [ABSTRACT FROM AUTHOR]

Ambient seismic noise has gained extensive applications in seismology and plays a pivotal role in environmental seismic studies. This study focuses on the Río de la Plata Coastal Plain, employing the horizontal-to-vertical spectral ratio (HVSR) method on ambient seismic noise records to analyze subsurface dynamics. The region's hydrogeology is complex, featuring partially interconnected coastal aquifers. The HVSR analysis reveals two peaks, with P0 associated with the sediment-basement interface and P1 linked to a shallower stratigraphic discontinuity. Temporal analysis of P1 highlights cyclical patterns correlated with estuarine levels, suggesting a relationship between variations in seismic velocities and tidal dynamics. Comparisons with aquifer data support the hypothesis that tidal variations influence subsurface mechanical properties, impacting the HVSR function. The study hints at the potential of ambient seismic noise analysis as a non-invasive and cost-effective method for studying coastal aquifers and understanding groundwater dynamics. Ongoing research aims to further explore these relationships for enhanced groundwater resource management. [ABSTRACT FROM AUTHOR]

This study employs a multimethod approach to investigate the sediment distribution in two pocket beaches, Ramla Beach and Mellieha S Beach, in Malta. Both study sites were digitally reconstructed using unmanned aerial vehicle (UAV) photogrammetry. For each case, an ERT and a dense network of ambient seismic noise measurements processed through a horizontal-to-vertical spectral ratio (HVSR) technique were acquired. Electrical resistivity tomography (ERT) analysis enables the estimation of sediment thickness in each beach. HVSR analysis revealed peaks related to beach sediments overlying limestone rocks in both sites and also indicated a deeper stratigraphic contact in Mellieha S Beach. Based on ERT measurements, sediment thickness is calculated for each HVSR measurement. Interpolation of results allows for bedrock surface modelling in each case study, and when combined with digital terrain models (DTMs) derived from photogrammetric models, sediment volumes are estimated for each site. The geometry of this surface is analyzed from a geological perspective, showing structural control of sediment distribution due to a normal fault in Mellieha S Beach and stratigraphic control facilitated by a highly erodible surface in Ramla Beach. The results emphasize the importance of adopting a three-dimensional perspective in coastal studies for precise sediment volume characterization and a deeper understanding of pocket beach dynamics. This practical multimethod approach presented here offers valuable tools for future coastal research and effective coastal management, facilitating informed decision making amidst the growing vulnerability of coastal zones to climate change impacts. [ABSTRACT FROM AUTHOR]

The aquifers of the Spanish Mediterranean coast are generally subjected to intense exploitation to meet the growing water supply demands. The result of the exploitation is salinization due to the marine saltwater intrusion, causing a deterioration in the quality of the water pumped, limiting its use for community needs, and not always being well delimited. To prevent deterioration, a groundwater control network usually allows precise knowledge of the areas affected by saltwater intrusion but not the extent of the saline plumes. Moreover, the characterization of aquifer systems requires a model that defines the geometry of aquifer formations. For this objective, we integrated hydrogeological, hydrogeochemical, and electrical resistivity subsoil data to establish a hydrogeological model of the coastal aquifer of Torredembarra (Tarragona, NE Spain). In this research, we have carried out a regional and local-scale study of the aquifer system to define the areas prone to being affected by saline intrusion (electrical resistivity values below 10 Ω·m). The obtained results could be used as a support tool for the assessment of the most favorable areas for groundwater withdrawal, as well as enabling the control and protection of the most susceptible areas to be affected by saltwater intrusion. [ABSTRACT FROM AUTHOR]

The Remolar beach-dune system (700 m long and more than 100 m wide, 070N direction) borders a campground that was closed (2003), due to the Barcelona airport expansion. In order to recover and restore the dune ecosystem, a series of soft measures were performed. After 10 years, a study of the morphology, sedimentology, and vegetation of the ecosystem was carried out to evaluate the results of these measures. For this purpose, a series of topographic and ground-penetrating radar (GPR) profiles, grain-size analysis, and an analysis of plant communities found along the profiles were carried out. The data obtained were compared with data from a former 2004 study. The results show that the morphology of the dunes recovered, and a new primary dune has arisen. The system now has a greater process of aggradation than of progradation. The vegetation has recovered the global composition of dune systems, with a typical community of embryo dunes and others of primary dunes that are set in strips parallel to the coast. Despite this improvement, the opportunistic and ruderal component in the primary dune vegetation evidences a strong anthropic inheritance in the system. [ABSTRACT FROM AUTHOR]

Managed aquifer recharge using surface or regenerated water plays an important role in the Barcelona Metropolitan Area in increasing storage volume to help operators cope with the runoff variability and unexpected changes in surface water quality that are aggravated by climate change. The specific aim of the research was to develop a non-invasive methodology to improve the planning and design of surface-type artificial recharge infrastructures. To this end, we propose an approach combining direct and indirect exploration techniques such as electrical resistivity tomography (ERT), frequency domain electromagnetics and data from double-ring infiltration tests, trial pits, research boreholes and piezometers. The ERT method has provided much more complete and representative information in a zone where the recharge project works below design infiltration rates. The geometry of the hydrogeological units and the aquifer-aquiclude contact are accurately defined through the models derived from the interpretation of ERT cross-sections in the alluvial aquifer setting. Consequently, prior to the construction of recharge basins, it is highly recommended to conduct the proposed approach in order to identify the highest permeability areas, which are, therefore, the most suitable for aquifer artificial recharge. [ABSTRACT FROM AUTHOR]