Shoreline variations and coastal dynamics: A space-time data analysis of the Jonian littoral, Italy

摘要

Morphological variations of coastlines are caused by several key processes that are influenced by climate conditions, sea level variations, wave energy, tectonics and human-induced phenomena. These processes affect the dynamics of catchment basins and the coastal environment. Since the second half of the 20th century, the Jonian coast of the Basilicata Region (Italy) has witnessed a widespread retreating phenomenon, predominantly due to anthropogenic causes affecting transport processes along the riverbeds and causing reductions in the sediment supply to the coast. The disturbance in the balance between sediment transport carried out by the sea and the sediment supply performed by rivers has led to a deficit in the sediment budget. To understand the morphological dynamics of the littoral environment and quantify the amount of coastal erosion, an analysis of coastline change has been carried out using various data sources: historical cartography, aerial photographs and GPS surveys. Between 1870 and 1954, the 32-km-long Jonian littoral under examination showed an accretion trend, while the loss in beach surface steadily increased between 1954 and 2005. The average change in beach surface has been calculated as about +55,000 m~2/yr (accretion) between 1870 and 1954 and -16,500 m~2/yr (erosion) between 1954 and 2005. Overall, 640,000 m~2 of sandy beaches were lost along the entire Jonian coast of the Basilicata Region between 1954 and 2005. Comparing the shoreline between 1870 and 1954, the average net shoreline movement (NSM) is +110 m vs. -30 m between 1954 and 2005. This analysis approach has proven to be effective in quantifying the erosion phenomenon and its effects, despite the lack of homogeneous data series and the variety of spatial and temporal scales over which coastal evolution occurs. The study represents an important step in understanding coastal dynamics in this region. As coastal areas are being affected by an increasing number of population and socio-economic activities, identification of shoreline changes and forecasts of coastline evolution represent key information for coastal scientists, engineers, decision makers and stakeholders for both the management of and development of future plans for coastal environments and for reducing exposure risk to coastal erosion.