Past and Recent Evolution of the Po River Delta and Emilia-Romagna Shoreline Continuum (Italy)

The continuum of shorelines in the Po River Delta and the Emilia-Romagna coast, located in the northwestern Adriatic Sea, is subjected to both natural and anthropogenic pressure that impact the way coastal geomorphology is altered throughout the territory. Hydrodynamical phenomenon associated with wind, waves and currents control the way sediment is transported through the shore and determine the amount of material is deposited. Moreover, high subsidence rate intensifies the coastal erosion putting the preservation of this coastal system at risk. Evaluating coastal dynamics can help understanding what aspects affect them the most. This study assesses the coastline evolution of the Emilia-Romagna region and the Po River Delta from the 1950s to 2020 by the Digital Shoreline Analysis System (DSAS), a software created by the United States Geological Survey (USGS). The Po River Delta shorelines for 70 years present an averaged linear regression rate (LRR) of -2.19 m/yr, net shoreline movement (NSM) of -130.51 m and end point rate (EPR) of -1.95 m/yr. For Emilia-Romagna, the 77 years of shoreline data, averaged LRR of -0.11 m/yr, NSM of -15.72 m and EPR of -0.2 m/yr, which are narrowly erosional, noting that respectively 59.4%, 56.4% and 56.4% of transects present accretion over the considered time interval. The Po River Delta statistics indicating an erosional trend are strongly related to fluvial sediment deficiency, that combined with wind-driven waves, storm surge and currents effects cause a decrease of the accumulated material at shore. The erosional rates of Emilia-Romagna were primarily linked to southward Reno River mouth relocation (suppressing the sediment supply) and gas and groundwater extraction from the soil (causing subsidence) to intensify coastal degradation. However, the majority of transects showing accretion indicate successful beach nourishments. Overall, coastal management and shoreline assessment play a crucial role in sustaining the coastline.