Paolo Emanuele Orrù

Mitigating flood risk and planning river corridors in Torrent-type Basins (TBs) requires integrated frameworks that link hydro-geomorphological processes with ecological quality, a combination currently lacking in regional planning. This study presents an integrated hydro-geomorphological and ecological analysis of the Rio Geremeas catchment (Sardinia, Italy), developed within the Regional Sediment Management Plan (PGS). The approach combines multi-scale geomorphological mapping, the IDRAIM eco-morphological framework, and 2D hydro-morphodynamic modelling (MIKE 21C), supported by field surveys and remote sensing of sediment source areas and biological assemblages (riparian vegetation, macroinvertebrates, and fish). Results reveal a direct link between altered sediment dynamics and ecological degradation, with confined reaches showing lower biotic diversity compared to mobile, morphologically functional reaches. 50-year flood simulations identified critical erosion/deposition zones, guiding targeted proposals: restoring sediment continuity by removing hydraulic constraints, controlling invasive species, and managing the river mouth to favour the migration of the European eel. This work provides a transferable, interdisciplinary approach for sediment- and ecosystem-informed river basin planning, directly supporting the EU Water Framework Directive and climate resilience strategies.

1. Coastal transgressive dune systems are large-scale, mobile, partially vegetated dune complexes that can decouple from the backshore and migrate inland over prior terrain, often cannibalising and...

Long-term impacts of sea-level changes and trends in storm magnitude and frequency along the Mediterranean coasts are key aspects of effective coastal adaptation strategies. In enclosed basins such as a gulf, this requires a step beyond global and regional analysis toward high-resolution modeling of hazards and vulnerabilities at different time scales. We present the compound future projection of static (relative sea level) and dynamic (wind-wave) impacts on the geomorphological evolution of a vulnerable sandy coastal plan located in south Sardinia (west Mediterranean Sea). Based on local temporal trends in H_s (8 mm yr⁻¹) and sea level (5.4 mm yr⁻¹), a 2-year return time flood scenario at 2100 shows the flattening of the submerged morphologies triggering the process of marine embayment. The research proposes adaptation strategies to be adopted to design the projected new coastal area under vulnerabilities at local and territorial scales.

Long-term impacts of sea-level changes and trends in storm magnitude and frequency along the Mediterranean coasts are key aspects of effective coastal adaptation strategies. In enclosed basins as a gulf, this requires a step beyond global and regional analysis toward high resolution modelling of hazards and vulnerabilities at different time scales. In this paper we present the compound future projection of static (sea level) and dynamic (wind-wave) impacts to the geomorphological evolution of a vulnerable sandy coastal plan located in the south Sardinia (west Mediterranean Sea). Based on local temporal trends in Hs (8 mm yr-1) and sea level (SLR of 5.4 mm yr-1), a 2-year return time flood scenario at 2100 shows the flattening of the submerged morphologies triggering the process of marine embayment. The research proposes adaptation strategies to be adopted to design the projected new coastal area under vulnerabilities at local and territorial scales.

In this paper, the physiography, geomorphological features, and sedimentary bedforms of the offshore Egadi Islands (Italy) have been illustrated and mapped through an integrated analysis of high-resolution bathymetric, seismo-acoustic, and sedimentological data. The study area is characterized by a wide, up to 25 km, continental shelf which is separated by a NNW-trending linear incision, the Marettimo Channel, along which several erosional and depositional features have been detected and mapped. Sedimentary prograding wedges were detected at water depths between 100–125 m along the shelf margin, which accumulated during the sea-level fall and lowstand stages of the last glacio-eustatic cycle (post- MIS 5.5). This study detected several slope breaks defining scarps across the continental shelf, which were interpreted as coastal cliffs that originated during the post-LGM eustatic sea-level rise. Several fields of different types of sedimentary bedforms, including 2-D and 3-D hydraulic dunes and sorted bedforms, were found across the continental shelf, providing evidence of a high hydrodynamic regime affecting the seafloor. Further on, this study recognized erosive and depositional features related to bottom currents (contourites) in the Marettimo Channel. These findings provide a better understanding of the morpho-sedimentary evolution of the Egadi Islands offshore in the latest Quaternary. Moreover, they offer essential scientific support for effectively managing the most valuable priority habitats for conservation, such as the Posidonia oceanica meadow and coralline algae bioconstructions (Coralligenous habitat).

We present a geomorphological map of the southwestern coast of Sardinia encompassing inland and offshore areas of the S’Omu e S’Orku Mesolithic site. The submerged area was documented by high-resolution multibeam bathymetry combined with Side-Scan Sonar data. The emerged coastal area was surveyed using Uncrewed Aerial Vehicle Remote Sensing and field surveys. The inland landforms were shaped by coastal, fluvial, and gravity-induced processes. Most of the submerged landforms appear be modeled in subaerial conditions during sea-level lowstands, and then sealed by the rising sea level. The coastal evolution has been characterized by the rapid cliff retreat facilitated intense linear erosion of watercourses, by debris flows, rockfalls and toppling. Geomorphological evidences of cliff retreat due to landslide was supported by a simplified analytic hydraulic model of the wave-cliff interaction. These processes and the sea level rise canceled any possible Mesolithic settlement along the coast. The survival of the S’Omu e S’Orku site is only due to a protected morphological position and to the distance from the Early Holocene coastline. The dearth of coastal Early Holocene prehistoric sites is likely the outcome of the presented coastal dynamics.

In Italy, landslides are one of the main geological hazards. Sometimes urban areas are affected by deep-seated gravitational slope deformations (DGSDs) that can lead to a potentially catastrophic failure and trigger a secondary collateral landslide. In these cases, monitoring is important for early warning and risk reduction. In this study, we analyzed DGSDs, in particular, lateral spreads, and landslides in the inhabited areas of Ulassai, in eastern-central Sardinia. Starting from high-resolution geostructural and geomorphological surveys of lateral spread, integrated with high-resolution digital elevation models acquired by UAV (Unmanned Aerial Vehicle), we created geological 3D models of the slope deformations. To better understand the kinematics and temporal evolution of unstable slope deformation, a monitoring system, consisting of Space-borne Interferometric Persistent Scatter Synthetic Aperture Radar (PS-InSAR), GNSS antennas, tiltmeters, and extensometers, was performed. PS-InSAR analysis confirmed by GNSS periodic measurement identified downslope movement of up to 10 mm per year in the lateral spread. Continuous acquisition by extensometers and tiltmeter recorder displacement in large block inclinations and opening and closing of fractures since 2021. Integrated data analysis will be essential to define the threshold for a future 24/7 early-warning system.

This paper shows the results of high-resolution survey on the continental shelf of Bonifacio Strait (north Sardinia). Multisensor and multiscale data obtained by means of sub-bottom profiler CHIRP and multibeam and side-scan sonar made it possible to identify the morphological features of bedforms. The analysis of both side-scan sonar sonograms mosaic and high-resolution seismic data allowed us to perform a detailed mapping of various substrates highlighting the presence of complex bedform associations. These bedform associations are typical of continental shelf environments affected by high-speed bottom currents. Multisource data analysis integrated by sedimentological study allowed us to identify the directions of sediment movements on the seabed and the progradation of bedforms. Locally, it was found that the bedforms of mobile bottoms are still active and they persist for more than a decade. The path of the currents’ circulation revealed that in the Bonifacio Strait, the bottom currents flow westwards, opposed to the prevailing sea surface flows.

Connections between Plio-Pleistocenic tectonic activity and geomorphological evolution were studied in the Pardu Valley and Quirra Valley (Ogliastra, East Sardinia). The intensive Quaternary tectonic activity in Sardinia linked to the opening of the Tyrrhenian Basin is known. In Eastern Sardinia, it manifests with an uplift that is recorded by geomorphological indicators, such as deep-seated gravitational slope deformation, fluvial captures, engraved valleys, waterfalls, and heterogeneous water drainage. The Pardu River flows from the NW toward the SE and then abruptly changes direction toward the NE. At this point, a capture elbow adjacent to the current head of the Quirra River is well developed. The Quirra River, in its upstream part, flows at altitudes approximately 200 m higher than the Pardu River. It also shows an oversized and over-flooded valley with respect to the catchment area upstream. This setting indicates that the Pardu River, which previously flowed south along the Quirra River, was captured by the Pelau River. We analyzed long-term landslides with lateral spreading and sackung characteristics, which involve giant carbonate blocks and underlying foliated metamorphites in both valleys. The use of LiDAR, high-resolution uncrewed aerial vehicle digital photogrammetry (UAV-DP), and geological, structural, and geomorphological surveys enabled a depth morphometric analysis and the creation of interpretative 3D models of DGSDs. Space-borne interferometric synthetic aperture radar (InSAR) data using ERS and Sentinel-1 satellites identified downslope movement of up to 20 mm per year in both Pardu Valley flanks. Multi-source and multi-scale data showed that the state of activity of the DGSDs is closely linked to the geomorphological evolution of the catchment areas of the Rio Pardu and Rio Quirra. The intense post-capture erosion acted in the Rio Pardu Valley, giving it morphometric characteristics that were favorable to the current evolution of the DGSDs, while the Rio Quirra Valley presents paleo-DGSDs that have been fossilized by pre-capture terraced alluvial deposits.