A geomatics approach to multitemporal shoreline analysis in western mediterranean: The case of platamona-maritza beach (Northwest Sardinia, Italy)

摘要

This study examines the shoreline change evolution at two spatiotemporal scales over ca. 18 km of Platamona-Maritza beach (northwest Sardinia, Italy). A multitemporal dataset spanning the period 19552010 was used and made up of archival aerial photographs, orthophotos, satellite imagery, light detection and ranging data, terrestrial laser scanner, Global Positioning System, and recent and historical topographic maps. We integrated this dataset by implementing a repeatable processing procedure, for which the global sensitivity for shoreline change estimation was evaluated (ca. 10 m as a product of time interval and change rate). The applied methodology indicates that the wet/dry boundary can be used as a good shoreline proxy. It is also demonstrated how reliable shoreline positional uncertainty (from 1.9 to 8.6 m) can be estimated whenever a large set of multitemporal data is available and geomatic tools are properly integrated. Results showed how shoreline evolutionary trends affected the entire coastal zone and roughly migrated from east to west, with the largest rates between 1970 and 2000. Where long-term analysis provided higher erosion rates, a sediment volumetric change was estimated, although only for a 2-year window and for a 300-m-wide stretch of beach. An analysis of geomorphic features along the coast also indicates variable longshore drift direction as a consequence of changes in a combination of wind, wave, and current regimes. A direct relationship between the evolutionary trend of hydrometric and pluviometric data recorded at the study site highlight that, although rainfall regime is nearly constant, average discharge of main rivers underwent a dramatic decrease since 1965 in conjunction with land use change and upstream dam construction for agriculture and urban development. Therefore, it has been argued that river sediment supply also was reduced; hence, besides other natural and anthropogenic causes, it likely influenced erosion and accretion events in the southern sector of the Gulf of Asinara.