Mariacristina Prampolini

Landslide susceptibility modeling assisted by Persistent Scatterers Interferometry (PSI): an example from the northwestern coast of Malta

Abstract Persistent Scatterers Interferometry (PSI) techniques are widely employed in geosciences to detect and monitor landslides with high accuracy over large areas, but they also suffer from physical and technological constraints that restrict their field of application. These limitations prevent us from collecting information from several critical areas within the investigated region. In this paper, we present a novel approach that exploits the results of PSI analysis for the implementation of a statistical model for landslide susceptibility. The attempt is to identify active mass movements by means of PSI and to avoid, as input data, time-/cost-consuming and seldom updated landslide inventories. The study has been performed along the northwestern coast of Malta (central Mediterranean Sea), where the peculiar geological and geomorphological settings favor the occurrence of a series of extensive slow-moving landslides. Most of these consist in rock spreads, evolving into block slides, with large limestone blocks characterized by scarce vegetation and proper inclination, which represent suitable natural radar reflectors for applying PSI. Based on geomorphometric analyses and geomorphological investigations, a series of landslide predisposing factors were selected and a susceptibility map created. The result was validated by means of cross-validation technique, field surveys and global navigation satellite system in situ monitoring activities. The final outcome shows a good reliability and could represent an adequate response to the increasing demand for effective and low-cost tools for landslide susceptibility assessment.

Advanced SAR Interferometric Analysis to Support Geomorphological Interpretation of Slow-Moving Coastal Landslides (Malta, Mediterranean Sea)

An advanced SAR interferometric analysis has been combined with a methodology for the automatic classification of radar reflectors phase histories to interpret slope-failure kinematics and trend of displacements of slow-moving landslides. To accomplish this goal, the large dataset of radar images, acquired in more than 20 years by the two European Space Agency (ESA) missions ERS-1/2 and ENVISAT, was exploited. The analysis was performed over the northern sector of Island of Malta (central Mediterranean Sea), where extensive landslides occur. The study was assisted by field surveys and with the analysis of existing thematic maps and landslide inventories. The outcomes allowed definition of a model capable of describing the geomorphological evolution of slow-moving landslides, providing a key for interpreting such phenomena that, due to their slowness, are usually scarcely investigated.

Late quaternary coastal landscape morphology and evolution of the Maltese Islands (Mediterranean Sea) reconstructed from high-resolution seafloor data

Abstract The current strong motivation to explore those traces of the archaeological and prehistoric human heritage that presently lie submerged on the continental shelf requires large-scale and precise underwater mapping. One Mediterranean sector deserving particular attention is the Sicily Channel, which is critical for a better understanding of the Africa–Europe migratory routes and early civilization patterns due to its large expanses of shallow seabed that were partially or totally exposed at times of lower relative sea levels. We have focused our attention on the submerged continental margin of the Maltese archipelago. A detailed bathymetric map is here presented, and is discussed in terms of features interpretable as former subaerial landforms and inundated by sea-level rise following the Last Glacial Maximum lowstand at approximately –130 m. Our datasets combine multibeam surveys, Light Detection And Ranging (LiDAR)-derived digital terrain models (DTMs), Chirp sub-bottom profiler records and bottom samples acquired between 2009 and 2012. The main features identified are former river incisions, alluvial plains, karst landscapes (sinkholes, limestone plateaus), slide deposits and palaeoshorelines. This study provides a detailed topographical reconstruction of the palaeolandscape of this key region that is relevant to any future archaeological exploration of the Maltese offshore area.

Geomorphological mapping of terrestrial and marine areas, northern Malta and Comino (central Mediterranean Sea)

ABSTRACT This paper presents an integrated geomorphological map of terrestrial and marine areas of northern Malta and Comino (central Mediterranean Sea) at 1:25,000 scale. The map is the result of terrestrial and marine analyses of different types of data such as aerial photos, digital terrain model of the seafloor and its acoustic backscatter image. The research is intended to emphasise the relationships and continuity of geomorphological features of both the land- and sea-scape, and outline their evolution. The map highlights the occurrence of fluvial, karst and gravity-induced landforms both on land and on the seafloor, such as palaeo-fluvial channels, sinkholes and landslides, which were shaped during sea level lowstands of the last glacial cycle.

High resolution multibeam and hydrodynamic datasets of tidal channels and inlets of the Venice Lagoon

Tidal channels are crucial for the functioning of wetlands, though their morphological properties, which are relevant for seafloor habitats and flow, have been understudied so far. Here, we release a dataset composed of Digital Terrain Models (DTMs) extracted from a total of 2,500 linear kilometres of high-resolution multibeam echosounder (MBES) data collected in 2013 covering the entire network of tidal channels and inlets of the Venice Lagoon, Italy. The dataset comprises also the backscatter (BS) data, which reflect the acoustic properties of the seafloor, and the tidal current fields simulated by means of a high-resolution three-dimensional unstructured hydrodynamic model. The DTMs and the current fields help define how morphological and benthic properties of tidal channels are affected by the action of currents. These data are of potential broad interest not only to geomorphologists, oceanographers and ecologists studying the morphology, hydrodynamics, sediment transport and benthic habitats of tidal environments, but also to coastal engineers and stakeholders for cost-effective monitoring and sustainable management of this peculiar shallow coastal system.

Geomorphology of the north-eastern coast of Gozo (Malta, Mediterranean Sea)

ABSTRACT The paper presents a geomorphological map of the north-eastern coast of the Island of Gozo (Malta) integrating inland and offshore areas at the scale 1:15,000. The map derives from the integration of different methods, such as aerial photo interpretation, field surveys and analysis of seafloor bathymetry. The landforms identified on land were shaped by coastal, fluvial, karst and gravity-induced processes, and some of them prolong on the seafloor. Most of the submerged landforms appear to have been modelled in subaerial conditions during sea-level lowstands, having been sealed by the rising sea in post-glacial times. Two sketches accompany the Main Map showing the type and distribution of coastal geomorphotypes and the land cover of the area.

INTEGRATED GEOMORPHOLOGICAL MAPPING OF THE EMERGED AND SUBMERGED NORTHERN AREA OF MALTA

Terrestrial and marine datasets referring to northe rn Malta (central Mediterranean Sea) have been collected and coupled in the frame of an inter national project funded by the EUR-OPA Major Hazards Agreement of the Council of Europe. O ne of the main outputs of the project is an integrated geomorphological map of the land and seascape of coastal areas of the northern sector of Malta. Existing geomorphological maps pro duced within the same project were used as a base for the mapping of the terrestrial areas. As regards submerged areas, several multibeam suveys were carried out offshore the east ern coasts of the archipelago and offshore the north-western coast of Malta to acquire high re solution bathymetry and backscatter data; a LiDAR-derived DEM of the northern area of Malta was used to cover the white zone between the bathymetric survey and the coastline. This larg e dataset allowed seafloor morphological features to be mapped and recognized by means of ba thymetric analysis and geomorphological interpretation. The seafloor sedim ents were analysed through grab samples collected offshore the eastern coasts of Malta and through the analysis of the acoustic textures characterising the seafloor backscatter imagery (Te xAn implemented by the University of Bath, UK) to produce a sediment distribution map. T he submerged geology was inferred by drawing geological sections based on the Geological Map of the Maltese Islands – Sheet 1 Malta. By exploiting all these data, an integrated g omorphological map of the northern area of Malta (from Marfa Ridge to the Great Fault) and the surrounding seafloors have been produced. The map clearly shows the differences cha ra terising the eastern and the western sides of the island. On the western side, the main features are related to gravity-induced processes responsible for the occurrence of differe nt types of coastal landslides prolonging under the sea level and making up the main landform s of the narrow continental shelf. On the eastern side of the island, the main features are r elated to fluvial and marine processes. Actually, the continental shelf is clearly cut thro ugh by a drainage network that is likely to have developed during sea level lowstands of the La st Glacial Maximum, when the sea level was about 130 m lower than at present.