The retreat of beaches in the world is increasingly evident., often due to a negative sediment balance. To prevent this, or at least to mitigate the effects of the retreat, were considered engineering structures and / or compensatory measures with results that were not always effective. Among the best measures, the artificial beach nourishment is well considered, because of its negligible environmental impact as well as for a discrete outcome with low costs. This intervention consists in sand dredging from the continental shelf, or from adjoining shorelines in progress, or even from the access channels to ports and then the discharge of it on the beach. The main difficulty is in identifying these "deposits of sediment" in the continental shelf which are considered the most relevant in terms of volume and likeness with the beach sediments adjacent to it. This contribution has attempted to extract automatically fOlIDS related to submerged ancient beach ridges, derived from the deposition of sand during the lowstands of the sea during the late Pleistocene, though a digital terrain model. The continental shelf, where the extraction was performed automatically. is placed at the south-eastern Tyrrhenian margin. It is in front to a high morphostructural, the Cilento promontory. bounded by the subsidence basins of the Gulf of Salerno - Piana del Sele River. NW. and Gulf of Policastro. SE. The map of this continental shelf seabed was performed using high-resolution bathymetric surveys totaling 675 km run with multibeam echo sounder at a rate not less than 50 kHz. insonificando the seabed in a bathymetric range between 0.5 to 150 m. Subsequently for the sedimentological characterization and. in particular, of the acoustic response on the type of bottom sediments marine mobile and its immediate substrate (SAVINI et al., 1995 cum bibl.), were evaluated for the same extension of the acoustic profiles with CHIRP sonar technology. high-resolution, The survey results were integrated with bathymetric charts of the Hydrographic Institute (1971). scale 1:100,000, appropriately georefereuced. with morphological and bathymetric data obtained from the geomorphological map in Ferraro et al. (1997) and with the morphological and sedimentary data collected from Pennetta (1996 a, b), De Pippo et al. (1996) and De Pippo and Pennetta (2000. 2004). All these data, taken together, allowed to obtain in a GIS environment the geomorphological map scale 1: 150.000 and to identify potentially areas for artificial beach nourishment. For the management and processing of data were used: the design software Autodesk Map 2008, which allowed the georeferencing of bathymetric charts of the Hydrographic Institute of the Navy and in the geomorphological Ferraro et al. (1997) in the reference system UT~II and interpolation of all the points relating to different depths, in order to obtain the preparation of the Charter Bathymetric. The processed data were exported to SHP in a condition suitable for use in other software environments, was then carried out a series of integrated applications of GIS ESRl ArcGIS Desktop 9.2, through which it was possible the drafting of other thematic maps. The applications used are ArcMap, ArcCatalog, and Arc'Toolbox, accompanied by instruments and controls GIS application ArcMap for all activities on mapping. editing and querying da.ta and apply ArcCatalog to organize and manage data. Through the application Arc Toolbox, organized collection of geoprocessing tools. operations were performed on GIS data available. The cartographic processing were represented in the reference system UTM. WGS 84 - ZONE 33N. The basis on which different calculations were made was identified in a Digital Elevation Model (DEM) of the area made using the data in depth, these values were obtained by digitizing the depth contours from the bathymetric map in scale 1:10,000. The detail of the data permitted high-resolution raster model used. consisting of cell sizes of 1Oxl 0 meters. In order to encode the entities geomorphological of interest, it was decided to analyze. from the point of view of the statistical distribution, the values relating t.o the key characteristics that can be derived starting from the The morphology that characterizes the platform, is rather articulated owing to the presence of faults in the substrate that generate displacements in the seabottom and therefore a structure of high and low areas, The platform is characterized by a wideness and an edge somewhat variable. The edge is located generally at a depth of 200 m except for the area overlooking the coastal stretch between Punta Licosa and Acciaroli, where it. reaches a depth of about 230 m, and for the southeastern area overlooking Punta Infreschi and the Gulf of Policastro, where it is much shallower with values lower than -100 m. The average gradient varies from 0.30 in the north and gradually increases going southward where in the narrowest portion of continental shelf reaches 0.8°. Its maximum width of about 30 kill is measured at north-west, and then it gradually shrinks down proceeding towards south-east, for instance, it is 13 km to the beam of the Telegraph Tower and 7 km offshore of Cape Palinuro. In the Gulf of Policastro, finally, it is characterized by a low wideness, which reaches 7.5 k111,and high slope gradients. On the platform were identified several limb of marine abrasion ten-aces with the edge located respectively at a depth of 30 m, 50 1119, 0 ui, 110111. 130 in, 140 m and 150 ill. Such terraces were modeled in coincidence of sea level changes occurred during the Pleistocene. Generally, they are evidenced from the hard substrate tha.t frequently rises from the bottom as well as from the irregular morphology surveyed at depths between 20 111 and 150 ill. Depressed areas were also recognised, filled by successions of sediments in various sizes. These areas are related to extensional processes occurred 011 the southeastern sector of the Tyrrhenian Sea. probably in the Plio-Pleistocene, along NW -SE direction. Instead. a depressed area, that connects with the valley of the River Alento. is controlled by faults with anti-Apenninic trend (NE-SW). as evidenced in the intermediate portion of the platform. We also identified some channels that cut the bottom. forming a paleo-drainage network of subaerial origin, whose outlets are fans of sediments similar to the mouth complex. detected through the analysis of the seabottom morphology. Among other geomorphological features shown in the geomorphological map, two elongated sedimentary bodies with a trend NW -SE are focused at a depth of between -120 and -170 III parallel to the edge of the platform. They extend for about 23 km offshore of Punta Licosa. 3.5 kHz subbottom profiles recognise these bodies as overhead structures from the bottom, where the sea side is always presented with a slope greater than the coast side. They are characterized by a type of echo with the bottom indistinct without reflections in the substrate (Ferraro et aI., 1997), indicating the presence of sandy deposits generally more reflective than the pelitic deposits. The top of these structures is irregular and sometimes is topped by a thin layer of Holocene sediments. DEM, ie elevation, slope, curvature and power of the relief.

Automated extraction of geomorphometric properties of relic sandy bodies in the continetal platform from a digital map geo-referenced in a GIS: the case of Cilento / Cartojan, E.; Guida, D.; Pennetta, Micla; Savini, A.; Siervo, V.; Valente, A.. - (2012), pp. 27-29. (Intervento presentato al convegno Objective Geomorphological Representation Models: Breaking through a New Geomorphological Mapping Frontier tenutosi a Salerno (Italy) nel October 15-19, 2012).

Automated extraction of geomorphometric properties of relic sandy bodies in the continetal platform from a digital map geo-referenced in a GIS: the case of Cilento.

PENNETTA, MICLA;
2012

Abstract

The retreat of beaches in the world is increasingly evident., often due to a negative sediment balance. To prevent this, or at least to mitigate the effects of the retreat, were considered engineering structures and / or compensatory measures with results that were not always effective. Among the best measures, the artificial beach nourishment is well considered, because of its negligible environmental impact as well as for a discrete outcome with low costs. This intervention consists in sand dredging from the continental shelf, or from adjoining shorelines in progress, or even from the access channels to ports and then the discharge of it on the beach. The main difficulty is in identifying these "deposits of sediment" in the continental shelf which are considered the most relevant in terms of volume and likeness with the beach sediments adjacent to it. This contribution has attempted to extract automatically fOlIDS related to submerged ancient beach ridges, derived from the deposition of sand during the lowstands of the sea during the late Pleistocene, though a digital terrain model. The continental shelf, where the extraction was performed automatically. is placed at the south-eastern Tyrrhenian margin. It is in front to a high morphostructural, the Cilento promontory. bounded by the subsidence basins of the Gulf of Salerno - Piana del Sele River. NW. and Gulf of Policastro. SE. The map of this continental shelf seabed was performed using high-resolution bathymetric surveys totaling 675 km run with multibeam echo sounder at a rate not less than 50 kHz. insonificando the seabed in a bathymetric range between 0.5 to 150 m. Subsequently for the sedimentological characterization and. in particular, of the acoustic response on the type of bottom sediments marine mobile and its immediate substrate (SAVINI et al., 1995 cum bibl.), were evaluated for the same extension of the acoustic profiles with CHIRP sonar technology. high-resolution, The survey results were integrated with bathymetric charts of the Hydrographic Institute (1971). scale 1:100,000, appropriately georefereuced. with morphological and bathymetric data obtained from the geomorphological map in Ferraro et al. (1997) and with the morphological and sedimentary data collected from Pennetta (1996 a, b), De Pippo et al. (1996) and De Pippo and Pennetta (2000. 2004). All these data, taken together, allowed to obtain in a GIS environment the geomorphological map scale 1: 150.000 and to identify potentially areas for artificial beach nourishment. For the management and processing of data were used: the design software Autodesk Map 2008, which allowed the georeferencing of bathymetric charts of the Hydrographic Institute of the Navy and in the geomorphological Ferraro et al. (1997) in the reference system UT~II and interpolation of all the points relating to different depths, in order to obtain the preparation of the Charter Bathymetric. The processed data were exported to SHP in a condition suitable for use in other software environments, was then carried out a series of integrated applications of GIS ESRl ArcGIS Desktop 9.2, through which it was possible the drafting of other thematic maps. The applications used are ArcMap, ArcCatalog, and Arc'Toolbox, accompanied by instruments and controls GIS application ArcMap for all activities on mapping. editing and querying da.ta and apply ArcCatalog to organize and manage data. Through the application Arc Toolbox, organized collection of geoprocessing tools. operations were performed on GIS data available. The cartographic processing were represented in the reference system UTM. WGS 84 - ZONE 33N. The basis on which different calculations were made was identified in a Digital Elevation Model (DEM) of the area made using the data in depth, these values were obtained by digitizing the depth contours from the bathymetric map in scale 1:10,000. The detail of the data permitted high-resolution raster model used. consisting of cell sizes of 1Oxl 0 meters. In order to encode the entities geomorphological of interest, it was decided to analyze. from the point of view of the statistical distribution, the values relating t.o the key characteristics that can be derived starting from the The morphology that characterizes the platform, is rather articulated owing to the presence of faults in the substrate that generate displacements in the seabottom and therefore a structure of high and low areas, The platform is characterized by a wideness and an edge somewhat variable. The edge is located generally at a depth of 200 m except for the area overlooking the coastal stretch between Punta Licosa and Acciaroli, where it. reaches a depth of about 230 m, and for the southeastern area overlooking Punta Infreschi and the Gulf of Policastro, where it is much shallower with values lower than -100 m. The average gradient varies from 0.30 in the north and gradually increases going southward where in the narrowest portion of continental shelf reaches 0.8°. Its maximum width of about 30 kill is measured at north-west, and then it gradually shrinks down proceeding towards south-east, for instance, it is 13 km to the beam of the Telegraph Tower and 7 km offshore of Cape Palinuro. In the Gulf of Policastro, finally, it is characterized by a low wideness, which reaches 7.5 k111,and high slope gradients. On the platform were identified several limb of marine abrasion ten-aces with the edge located respectively at a depth of 30 m, 50 1119, 0 ui, 110111. 130 in, 140 m and 150 ill. Such terraces were modeled in coincidence of sea level changes occurred during the Pleistocene. Generally, they are evidenced from the hard substrate tha.t frequently rises from the bottom as well as from the irregular morphology surveyed at depths between 20 111 and 150 ill. Depressed areas were also recognised, filled by successions of sediments in various sizes. These areas are related to extensional processes occurred 011 the southeastern sector of the Tyrrhenian Sea. probably in the Plio-Pleistocene, along NW -SE direction. Instead. a depressed area, that connects with the valley of the River Alento. is controlled by faults with anti-Apenninic trend (NE-SW). as evidenced in the intermediate portion of the platform. We also identified some channels that cut the bottom. forming a paleo-drainage network of subaerial origin, whose outlets are fans of sediments similar to the mouth complex. detected through the analysis of the seabottom morphology. Among other geomorphological features shown in the geomorphological map, two elongated sedimentary bodies with a trend NW -SE are focused at a depth of between -120 and -170 III parallel to the edge of the platform. They extend for about 23 km offshore of Punta Licosa. 3.5 kHz subbottom profiles recognise these bodies as overhead structures from the bottom, where the sea side is always presented with a slope greater than the coast side. They are characterized by a type of echo with the bottom indistinct without reflections in the substrate (Ferraro et aI., 1997), indicating the presence of sandy deposits generally more reflective than the pelitic deposits. The top of these structures is irregular and sometimes is topped by a thin layer of Holocene sediments. DEM, ie elevation, slope, curvature and power of the relief.
2012
Automated extraction of geomorphometric properties of relic sandy bodies in the continetal platform from a digital map geo-referenced in a GIS: the case of Cilento / Cartojan, E.; Guida, D.; Pennetta, Micla; Savini, A.; Siervo, V.; Valente, A.. - (2012), pp. 27-29. (Intervento presentato al convegno Objective Geomorphological Representation Models: Breaking through a New Geomorphological Mapping Frontier tenutosi a Salerno (Italy) nel October 15-19, 2012).
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11588/565641
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