This paper presents geomorphological and engineering-geological studies carried out along the north-western coast of Malta by research groups belonging to the University of Modena and Reggio Emilia (Italy), the National Research Council (Italy), the University of Malta and the University of Cantabria (Spain). The research are funded by Fondazione Cassa di Risparmio di Modena and the European Centre for Geomorphological Hazards (CERG) and focus on the evolution of coastal landslides with emphasis on the issues of hazard and risk, with respect to the recreational infrastructures present in the area and to the several tourists that visit this stretch of coast. The area of study extends for about 12 km2 in Northern Malta and elevation ranges from the coast to about 110 m above the sea level. In this part of the Island, slope failures are abundant and strictly linked to lithological and structural factors. In fact, in the north-western area of Malta, between Paradise Bay and Gnejna Bay, three geological units outcrop that deeply control the morphological setting and the evolution of landscape: Globigerina Formation, Blue Clay Formation and Upper Coralline Formation. The Upper Coralline Limestone, the younger Formation of Malta Island, forms a karst plateau, bordered by vertical cliffs of varying heights, which ranges from a few meters to 30 m. At the foot of the limestone slopes Blue Clays Formation crops out which develops gently slopes that in some cases can reach directly the sea. The different mechanical behaviour of clays and limestone favours the development of lateral spreading phenomena, which occur in particular at Anchor Bay, at Ghajn Tuffieha Bay and along the western sector of Marfa Ridge. The occurence of this type of mass movement causes the presence of vertical joints and cracks near the calcareous slopes, due to the fragile response of rock material. Properties of the cracks, such as their aperture and persistence, depend on the different stages of lateral spreading phenomena; in the areas where the phase of evolution is more mature fractures reach lengths that can exceed 200 meters. A consequence of the presence of these wide discontinuities is the accumulation of large boulders along the coast, due to the detachament and fall of blocks from the vertical cliffs. The deposits are wide and the blocks are slowly scattered on the large terrace gently sloping towards the sea. In order to study and understand the complex evolution of coastal slope failures, a multidisciplinary approach has been applied and a complex system of monitoring has been installed. The research carried out so far has included a retrospective study of slope instability events along the north-west coast of Malta, collection and analysis of climatic data, multi-temporal analysis of aerial photos, geomorphological survey and mapping. In addition, the research plan foresees LIDAR surveys and radar interferometric analyses. The results obtained have permitted to outline the causes and evolution of coastal landslides in the north-western coast of Malta, with specific focus on rock spreading phenomena whose movement velocity and direction have been monitored since 2006 in two field sites. GPS network are located at Il-Qarraba and Anchor Bay. The analysis of monitoring data has shown that lateral spreading phenomena are active in both sites and that the displacements range from a few mm/yr to more then 3 cm/yr. The integration of new monitoring data to be acquired will permit the evaluation and mapping of landslide hazard. The final results of the research are aiming at providing local authorities with a sound knowledge of coastal instability phenomena which might be useful for future land planning and in managing geomorphological risk issues.

A comprehensive approach to investigate maltese coastal landslides / Soldati, Mauro; Bonachea, Jaime; Maria Bruschi, Viola; Coratza, Paola; Devoto, Stefano; González-Díez, Alberto; Mantovani, Matteo; Pasuto, Alessandro; Piacentini, Daniela; Remondo, Juan; Schembri, John A.. - In: JOURNAL OF COASTAL RESEARCH. - ISSN 0749-0208. - (2011), pp. 472-473. [10.2112/SI61-001.62]

A comprehensive approach to investigate maltese coastal landslides

Daniela Piacentini;
2011

Abstract

This paper presents geomorphological and engineering-geological studies carried out along the north-western coast of Malta by research groups belonging to the University of Modena and Reggio Emilia (Italy), the National Research Council (Italy), the University of Malta and the University of Cantabria (Spain). The research are funded by Fondazione Cassa di Risparmio di Modena and the European Centre for Geomorphological Hazards (CERG) and focus on the evolution of coastal landslides with emphasis on the issues of hazard and risk, with respect to the recreational infrastructures present in the area and to the several tourists that visit this stretch of coast. The area of study extends for about 12 km2 in Northern Malta and elevation ranges from the coast to about 110 m above the sea level. In this part of the Island, slope failures are abundant and strictly linked to lithological and structural factors. In fact, in the north-western area of Malta, between Paradise Bay and Gnejna Bay, three geological units outcrop that deeply control the morphological setting and the evolution of landscape: Globigerina Formation, Blue Clay Formation and Upper Coralline Formation. The Upper Coralline Limestone, the younger Formation of Malta Island, forms a karst plateau, bordered by vertical cliffs of varying heights, which ranges from a few meters to 30 m. At the foot of the limestone slopes Blue Clays Formation crops out which develops gently slopes that in some cases can reach directly the sea. The different mechanical behaviour of clays and limestone favours the development of lateral spreading phenomena, which occur in particular at Anchor Bay, at Ghajn Tuffieha Bay and along the western sector of Marfa Ridge. The occurence of this type of mass movement causes the presence of vertical joints and cracks near the calcareous slopes, due to the fragile response of rock material. Properties of the cracks, such as their aperture and persistence, depend on the different stages of lateral spreading phenomena; in the areas where the phase of evolution is more mature fractures reach lengths that can exceed 200 meters. A consequence of the presence of these wide discontinuities is the accumulation of large boulders along the coast, due to the detachament and fall of blocks from the vertical cliffs. The deposits are wide and the blocks are slowly scattered on the large terrace gently sloping towards the sea. In order to study and understand the complex evolution of coastal slope failures, a multidisciplinary approach has been applied and a complex system of monitoring has been installed. The research carried out so far has included a retrospective study of slope instability events along the north-west coast of Malta, collection and analysis of climatic data, multi-temporal analysis of aerial photos, geomorphological survey and mapping. In addition, the research plan foresees LIDAR surveys and radar interferometric analyses. The results obtained have permitted to outline the causes and evolution of coastal landslides in the north-western coast of Malta, with specific focus on rock spreading phenomena whose movement velocity and direction have been monitored since 2006 in two field sites. GPS network are located at Il-Qarraba and Anchor Bay. The analysis of monitoring data has shown that lateral spreading phenomena are active in both sites and that the displacements range from a few mm/yr to more then 3 cm/yr. The integration of new monitoring data to be acquired will permit the evaluation and mapping of landslide hazard. The final results of the research are aiming at providing local authorities with a sound knowledge of coastal instability phenomena which might be useful for future land planning and in managing geomorphological risk issues.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11573/1585044
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